GIFT OF 
 
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MANUAL 
 
 OF 
 
 ELEMENTARY GEOLOGYr 
 
 OB, 
 
 THE ANCIENT CHANGES OF THE EARTH AND ITS INHABITANTS 
 AS ILLUSTRATED BY GEOLOGICAL MONUMENTS. 
 
 BY SIR CHARLES LTELL, M.A. F.R.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." 
 
 EDIHBUBGH RIVIEW, July, 1837. 
 
 HDMMOI.IT3. A1C1COVITB. TRH.OBIT* 
 
 TERTIARY. SECONDARY. PRIMARY. 
 
 KEPRINTED FROM THE SIXTH EDITION, GREATLY ENLARGED. 
 
 SUustraUU toftji 750 oottcuts. 
 
 NEW YORK: 
 D. APPLETON AND COMPANY, 
 
 846 & 348 BEOADWAY. 
 
 1858. 
 
A* 
 
 
 ENGINEERING LIBRARY 
 
PREFACE 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 previously 
 acquired stock of knowledge. In iny 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 Illustrations 
 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 follow- 
 ing summary of the more important additions and alterations. 
 
 Principal Additions and Alterations in the present Edition. 
 
 CHAP. IX. "The general Table of Fossiliferous strata," formerly 
 placed at the end of Chapter Xx'yi'f., is now given at p. 104, that the 
 beginner may accustom himself from the first to refer to it from time to 
 time when studying the numerous subdivisions into which it is now 
 necessary to separate the chronological 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 con- 
 temporaneous 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 Society of London for 
 
 855672 
 
VI PEEFACE TO THE FIFTH EDITION". 
 
 1852. In the course of my investigations I enjoyed opportunities of 
 determining more exactly the relations of the Antwerp and the Suffolk 
 crag, p. 173 ; the stratigraphical place of the Bolderberg beds near 
 Hasselt, p. 178 ; that of the Limburg or Kleyn Spawen strata, p. 188 ; 
 and of other Belgian and French deposits. In reference to some of these, 
 the questions so much controverted of late, whether certain groups should 
 be called Lower Miocene or Upper Eocene, are fully discussed, p. 183, 
 et seq. 
 
 In the winter of 1852, 1 had the advantage of examining the northern 
 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. 185-192), recognized by him as the equivalent 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 Bag- 
 shot beds. An account of these discoveries, with the names of the new 
 subdivisions, is given at pp. 208 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. 221, 
 and the relations of the Middle and Lower Eocene of France to various 
 deposits in the Isle of Wight and Hampshire at p. 222 et seq. In the 
 same chapters, many figures have been introduced of characteristic or- 
 ganic 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. 235. 
 
 CHAP. XVm. 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. 263. 
 
 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 introduced. 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 endeavored 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 prob- 
 lem by an appeal to ordinary causation, or to invoke the aid of imagi- 
 nary catastrophes and paroxysmal violence, pp. 271-290. 
 
 CHAP. XX. XXI. On the strata from the Oolite to the Lias inclu- 
 sive. The Purbeck beds are here for the first time considered as the 
 uppermost member of the Oolite, in accordance with the opinions of the 
 
PREFACE TO THE FIFTH EDITION. vii 
 
 late Professor E. Forbes, p. 294. Many new figures of fossils character- 
 istic of the subdivisions of the three Purbecks are introduced ; and the 
 discovery, in 1854, of a new mammifer alluded to, p. 295. 
 
 Representations also of fossils of the Upper, Middle, and Lower Oolite, 
 and of the Lias, are added to those before given. 
 
 CHAP. XXTT. XX1L1. On the Triassic and Permian formations. 
 The improvements consist chiefly of new illustrations of fossil remains. 
 
 CHAP. XXfV. XXY. Treating of the Carboniferous group, I have 
 mentioned the subdivisions now generally adopted for the classification of 
 the Irish strata (p. 359), and I have added new figures of fossil plants to 
 explain, among other topics, the botanical characters of Calamites, Stern- 
 bergia, and Trigonocarpum, and their relation to Coniferae (pp. 364, 365, 
 368). The grade also of the Coniferse in the vegetable kingdom, and 
 whether they hold a high or a low position among flowering plants, is dis- 
 cussed with reference to the opinions of several of the most eminent 
 living botanists ; and the bearing of these views on the theory of progres- 
 sive development, p. 3 TO. 
 
 The casts of rain-prints in coal-shale are represented in several wood- 
 cuts as illustrative of the nature and humidity of the carboniferous 
 atmosphere, p. 381. The causes also of the purity of many seams of 
 coal, p. 382, and the probable length of time which was required to 
 allow the solid matter of certain coal-fields to accumulate, p. 383, are 
 discussed for the first time. 
 
 Figures are given of Crustaceans and Insects from the Coal, pp. 
 385, 386 ; and the discovery of some new Reptiles is alluded to, p. 401. 
 
 I have also alluded to the causes of the rarity of vertebrate and inver- 
 tebrate air-breathers in the coal, p. 401. 
 
 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 Paleozoic, as distin- 
 guishable from those of the Neozoic, type, p. 403 ; also by woodcuts of 
 several genera of shells which retain the patterns of their original colors, 
 p. 406. The foreign equivalents of the Mountain Limestone are also 
 alluded to, p. 409. 
 
 CHAP. XXVL In speaking of the Old Red Sandstone, or Devonian 
 Group, the evidence of the occurrence of the skeleton of a Reptile and 
 the footprints of a Chelonian in that series are reconsidered, p. 412. 
 New plants found in Ireland in this formation are figured, p. 414 ; also 
 the Pterygotus, or large crustacean of Forfarshire, p. 415 ; and, lastly, the 
 division of the Devonian series in North Devon into Upper, Middle, and 
 Lower, p. 420, the fossils of the same (p. 421 et seq.), and the equivalents 
 of the Devonian beds in Russia and the United States, are treated of, 
 p. 425 and 428. 
 
 CHAP. XXVII. The classification and nomenclature of the Silurian 
 rockg of Great Britain, the Continent of Europe, and North America, and 
 the question whether they can be distinguished from the Cambrian, and 
 
Vlll PKEFACE TO THE FIFTH EDITION. 
 
 by what paleontological characters, are discussed in this chapter, pp. 429, 
 447, and 453. 
 
 The relation of the Caradoc Sandstone to the Upper and Lower Silu- 
 rian, as inferred from recent investigations (p. 437), the vast thickness of 
 the Llandeilo or Lower Silurian in Wales (p. 442), the Obolus or Ungu- 
 lite grit of St. Petersburg and its fossils (p. 443), the Silurian strata of 
 the United States and their British equivalents (p. 444), and those of 
 Canada, the discoveries of M. Barrande respecting the metamorphosis of 
 Silurian and Cambrian trilobites (pp. 441, 450), 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 likewise 
 described as they exist in Wales, Ireland, Bohemia, Sweden, the United 
 States, and Canada, and some of their peculiar organic remains are fig- 
 ured, p. 447 to p. 453. 
 
 Lastly, at the conclusion of the chapter, some remarks are offered re- 
 specting the absence of the remains of fish and other vertebrata from the 
 deposits below the Upper Silurian, p. 453, in elucidation of which topic 
 a Table has been drawn up of the dates of the successive discovery of dif- 
 ferent classes of Fossil Vertebrata in rocks of higher and higher anti- 
 quity, showing the gradual progress made in the course of the last 
 centuiy 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 development is then discussed, and the 
 grounds of the supposed scarcity both of vertebrate and invertebrate air- 
 breathers in the most ancient formation considered, p. 456. 
 
 CHAP. XXVni. With the assistance of an able mineralogist, M. 
 Delesse, I have revised and enlarged the glossary of the more abundant 
 volcanic rocks, p. 472, and the table of analyses of simple minerals, 
 p. 475. 
 
 CHAP. XXIX. In consequence of a geological excursion to Madeira 
 and the Canary Islands, which I made in the winter of 1853-4, 1 have 
 been enabled to make larger additions of original matter to this chapter 
 than tc any other in the work. The account of Tenerifie and Madeira, 
 pp. 510, 518, 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. 494-508. Many illustrations, 
 chiefly from the pencil of my companion and fellow-laborer, Mr. Hartung, 
 have been introduced. In reference to the above-mentioned subjects, 
 citations are made from Dana on the Sandwich Islands, p. 489, and from 
 Junghuhn's Java, p. 492. 
 
 CHAP. XXXV. XXXVII. The theory of the origin of the meta- 
 morphic rocks and certain views recently put forward by some geolo- 
 gists respecting cleavage and foliation have made it desirable to recast 
 
PKEFACE TO THE FIFTH EDITION. ix 
 
 and rewrite a portion of these chapters. New proofs are cited in favor of 
 attributing cleavage to mechanical force, p. 603, and for inferring in many 
 cases a connection between foliation and cleavage, p. 608. At the same 
 time, the question how far the planes of foliation usually agree with 
 those of sedimentary deposition, is entered into, p. 607. 
 
 CHAP. XXXVIII. 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 labors. His 
 friendship, and the power of referring to his sound judgment in 
 cases of difficulty on paleontological 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- 
 cellences, would have inspired a large portion of the rising 
 generation with kindred enthusiasm for branches of knowledge 
 nitherto 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 
 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 
 
X PEEFACE TO THE FIFTH EDITION. 
 
 geology, 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, 1838, into a separate treatise called the " Elements 
 of Geology," first re-edited in 1842, and again recast and en- 
 larged in 1851, and entitled " A Manual of Elementary Geol- 
 ogy." 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 " Princi- 
 ples" 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 ene from the other, I 
 have endeavored to render each complete in itself, and inde- 
 pendent ; 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 
 present 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 
 connection which Chemistry bears to Natural Philosophy, each 
 being subsidiary to the other, and yet admitting of being con- 
 sidered as different departments of science.* 
 
 CHAELES LYELL. 
 
 53 Barley-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 L On the different Classes of Rock*. 
 
 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 < - - I* a ge 1 
 
 CHAPTER II. Aqueous Rocks Their Composition and Forms of Stratification. 
 
 Mineral composition of strata Arenaceous rocks Argillaceous Calcareous 
 Gypsum Forms of stratification Diagonal arrangement Ripple-mark 10 
 
 CHAPTEE IH Arrangement of Fossils in Strata Freshwater and Marine. 
 
 Limestones formed of corals and shells Proofs of gradual increase of strata de- 
 rived from fossils Tripoli and semi-opal formed of infusoria Chalk derived 
 principally from organic bodies Distinction of freshwater from marine forma- 
 tions Alternation of marine and freshwater deposits - - 21 
 
 CHAPTEE IV. Consolidation of Strata and Petrifaction of Fossils. 
 
 Chemical and mechanical deposits Cementing together of particles Concre- 
 tionary 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 posi- 
 tion of disturbed strata Unconfonnable stratification Fractures of strata 
 Faults .... .... 44 
 
 CHAPTER VL 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 VLL 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 VHL 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 nomenclature adopted in this work, so far as regards primary, 
 secondary, and tertiary periods .... 89 
 
xii 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 Dis- 
 tinct 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 - L - ' - - 109 
 
 CHAPTER XI. Newer Pliocene Period. Boulder Formation. 
 
 Drift of Scandinavia, northern Germany, and Russia Fundamental rocks pol- 
 ished, grooved, and scratched Action of glaciers and icebergs Fossil shells 
 of glacial period Drift of eastern Norfolk Ancient glaciers of North Wales 
 Irish drift - - 126 
 
 CHAPTER XII. Boulder Formation continued. 
 
 Effects of intense cold in augmenting the quantity of alluvium Analogy of er- 
 ratics 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 Me- 
 teorite in Asiatic drift - - < "' - - - 137 
 
 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 Relation- 
 ship of geographical provinces of living vertebrata and those of Pliocene species 
 Teeth of fossil quadrupeds - - - - -152 
 
 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 glacial period Antwerp crag Subapennine beds Miocene forma- 
 ifans 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 .r%: - - - - 167 
 
 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 
 Auvcrgne and the Cantal Upper Eocene of Bordeaux, <fec. Of Nebraska, 
 United States ........ 188 
 
 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 for- 
 mations of France Nummulitic formations of Europe and Asia Eocene 
 strata at Claiborne, Alabama Colossal cetacean Orbitoid limestone Burr 
 atone - - -*' * ..... 207 
 
CONTENTS. xiii 
 
 CHAPTER XVIL Cretaceous Group. 
 
 Lapse of time between the Cretaceous and Eocene periods Formations in Bel- 
 gium and France of intermediate age Pisolitic limestone Divisions of the 
 Cretaceous series in Northwestern 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 Hippurite limestone Cretaceous rocks of the United States 234 
 
 CHAPTEE XVHL 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 re- 
 lation to the Cretaceous type Flora of Lower Cretaceous and Wealdea 
 periods ...--.--- 256 
 
 CHAPTER XIX. Denudation of the Chalk and Wealden. 
 
 Physical geography of certain districts tcomposed 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 Kise and denudation of the strata gradual 
 At what period the Weald valley was denuded, and by what causes Ele- 
 phant-bed, Brighton Sangatte cliff Conclusion - - - 267 
 
 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 Inferior Oolite and fossils - * * - 291 
 
 CHAPTER XXL Jurassic Group, continued. Lias, 
 
 Mineral character of Lias Fossil shells and fish Radiata Ichthyodorolites 
 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 - .... 317 
 
 CHAPTER XXII. Trias or New Red Sandstone Group. 
 
 Distinction between New and Old Red Sandstone The Trias and its three di 
 visions in Germany Keuper and its fossils Muschelkalk and fossils Fossil 
 plants of the Bunter Triassic group in England Footsteps of Cheirotherium 
 Osteology of the Ldbyrinlhodon Triassic mammifer Origin of Red Sand- 
 stone and Rock-salt New Red Sandstone in the United States Fossil foot- 
 prints of birds and reptiles in the valley of the Connecticut - - 332 
 
 CHAPTER XXUL Permian or Magnesian Limestone Group. 
 
 Fossils of Magnesian Limestone Term Permian English and German equiva- 
 lents Marine shells and corals Palaeoniscus and other fish Thecodont sau- 
 rians Permian Flora Its generic affinity to the carboniferous Psaronites or 
 tree-ferns ---- .... 350 
 
 CHAPTER XXIV. The Coal, or Carboniferous Group. 
 
 Carboniferous strata in England Coal-measures and mountain limestone Car- 
 boniferous series in Ireland and South Wales Underclays with Stigmaria 
 Carboniferous Flora Ferns, Lepidodendra, Calamites, Sigillariae Coniferae 
 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 Crusta- 
 ceans and insects - - - - - - 358 
 
CONTENTS. 
 
 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 Page 387 
 
 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, <fcc., crustaceans, of Caithness and Forfarshire Dis- 
 tinct 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 - - - - - 411 
 
 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 Wen- 
 lock formation, corals, cystideans, trilobites Caradoc sandstone Pentameri 
 and Tentaculites Lower Silurian rocks Llandeilo flags Cystidese Trilo- 
 bites Graptolites Vast thickness of Lower Silurian strata in Wales Foreign 
 Silurian equivalents in Europe Ungulite grit of Russia Silurian strata 01 
 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 trilobites 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 prema 
 ture - - - 429 
 
 CHAPTER XXVIIL 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 analyses of minerals most abundant in 
 the volcanic and hypogene rocks - - * i~ ' - , - 460 
 
 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 volcanoes Form, exter- 
 nal structure, and origin of volcanic mountains Craters and Calderas Sand 
 wich 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 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 how formed - - - - 476 
 
CONTENTS. XV 
 
 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 character 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 Soinma Igneous formations of the Newer Plio- 
 cene period Val di Noto in Sicily - Page 519 
 
 CHAPTER "X"X"XT. On the Different Ages of the Volcanic Rocks 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 characters of the volcanoes of the Upper and Lower Eifel Lake craters 
 Trass Hungarian volcanoes - - - 630 
 
 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 quadru- 
 peds buried in scoriae Cantal Eocene volcanic rocks Tuffs near Clermont 
 Hill of Gergovia Trap of Cretaceous period Oolitic period New Red Sand- 
 stone period Carboniferous period Old Red Sandstone period Silurian pe- 
 riod Cambrian volcanic rocks ...-.- 545 
 
 CHAPTER XXXIIL Plutonic Rocks Granite. 
 
 General aspect of granite Analogy and difference of volcanic and plutonic for- 
 mations 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 Whether plutonic rocks are ever overlying Their exposure 
 at the surface due to denudation - - 560 
 
 CHAPTER XXXIV. On the different Ages of the Plutonic Rocks. 
 
 Difficulty in ascertaining the age of a plutonic rock Test of age by relative posi- 
 tion Test by intrusion and alteration Test by mineral composition Test by 
 included fragments Recent and Pliocene plutonic rocks, why invisible Ter- 
 tiary 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 protruded in a solid form Age of the granites of Arran, in 
 Scotland - ... . - 573 
 
 CHAPTER XXXV. Metamorphic Rocks. 
 
 General character of metamorphic rocks Gneiss Hornblende-schist Mica- 
 schist Clay-slate Quartzite Chlorite-schist Metamorphic limestone Al- 
 phabetical 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 meta- 
 morphic series Objections to the metamorphic theory considered Partial 
 conversion of Eocene slate into gneiss - - 587 
 
 CHAPTER XXXVL 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 - 600 
 
XVI CONTENTS. 
 
 CHAPTER XXXVIL On the different Ages of the Metamorphic Rocks. 
 
 Age of each set of metamorphic strata twofold Test of age by fossils and min- 
 eral character not available Test by superposition ambiguous Conversion of 
 fossiliferous strata into metamorphic rocks Limestone and shale of Carrara 
 Metamorphic 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 - - Page 611 
 
 CHAPTER XXXVIII. 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 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 Connec- 
 tion of hot springs and mineral veins Concluding remarks :..' ^ . 618 
 
 SUPPLEMENT. 
 
 British Pliocene Strata Proofs from fossil shells of a gradual refrigeration of climate 
 in England, at the successive periods of the Coralline, the Red, and the Norwich 
 Crag Searles Wood's Monograph on the Crag Mollusca The Crag Mastodon, a 
 Pliocene species Different assemblages of fossil Mammalia in the freshwater and 
 drift deposits of the valley of the Thames Fossil Musk-buffalo in the drift near 
 London and near Berlin - ... p a g e 635 
 
 Where to draw the line "between the Miocene and Eocene Tertiary Strata. 
 
 Classification of the Miocene and Eocene strata Where to draw the line between 
 Upper Eocene and Lower Miocene Reasons for a proposed change of nomen- 
 clature Miocene fossil shells and quadrupeds of the Sewalik or Sub-Hiinalayan 
 Hills - - - - - - - - - - 640 
 
 Miocene Fauna of the Sewalik Hitts .... 645 
 
 Denudation of the Wealdenr Discovery of the Lower Crag on the summit of the 
 North Downs between Folkestone and Dorking - 645 
 
 New Fossil Mammalia from the Purbeck or Upper Oolitic Strata in Dorsetshire. 
 Discovery in Dorsetshire of seven or eight new genera of Mammalia in the Purbeck 
 or Upper Oolite strata First example of a skull of a Mammifer from Secondary 
 Rocks Insectivorous Marsupials and Placentals and herbivorous Marsupials 
 Figures and descriptions Light thrown on the Microlestes or oldest triassic Mam- 
 mifer General bearing of the new facts - - 647 
 
 Discovery of Mammalian Remains in Rocks of high Antiquity in] North Carolina, 
 United States - - - - - - - - - 659 
 
 Upper Trias of the Eastern Alps. Recognition of a Marine equivalent of the Upper 
 Trias in the Austrian Alps True position of the St. Cassian and Hallstatt Beds 
 800 new species of triassic Mollusca and Radiata Links thus supplied for connect- 
 ing the Palaeozoic and Neozoic faunas 660 
 
 On the supposed evidence of Phcenogamous Plants (not Gymnosperms) in the Coal 
 Formation ...----_. 663 
 
 Sihvrian and Cambrian Rocks and M. BarrandJs theory of Colonies - - 664 
 Antiquity of Fossil Birds - 669 
 
MANUAL 
 
 OF 
 
 ELEMENTARY GEOLOGY. 
 
 CHAPTER I. , 
 
 ON THE DIFFERENT CLASSES OF ROCKS. 
 
 Geology defined Successive formation of the earth's crust Classification d 
 rocks according to their origin and age Aqueous rocks Their stratification 
 and imbedded fossils Volcanic rocks, with and without cones and craters 
 Plutonic rocks, and their relation to the volcanic Metamorphic rocks and their 
 probable origin The term primitive, why erroneously applied to the crystal- 
 line 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 y?j, ge, the 
 earth, and Xoyos, 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, inhabited the globe. 
 
 All are aware that the solid parts of the earth consist of distinct sub- 
 stances, such as clay, chalk, sand, limestone, coal, slate, granite, and the 
 like; but previously to observation it is commonly imagined that all 
 these had remained from the first in the state in which we now see 
 them, that they were created in their present form, and in their present 
 position. The geologist soon comes to a different conclusion, 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 condition gradually, under a great variety 
 
2 CLASSIFICATION OF ROCKS. [On. 1 
 
 of circumstances, and at successive periods, during each of which distinct 
 races of living beings have flourished on the land and in the waters, the 
 remains of these creatures still lying buried in the crust of the earth. 
 
 By the " earth's crust," is meant that small portion of the exterior of 
 our planet which is accessible to human 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 ^^ 
 part of the distance from the surface to the centre. The remark is just ; 
 but although the dimensions of such a crust are, in truth, insignificant 
 when compared to the entire globe, yet they are vast, and of magnificent 
 extent in* relation to man, and to the organic beings which people our 
 l ciob^"' inferring to this standard of magnitude, the geologist may 
 admire tfye Cmple limits of his domain, and admit, at the same time, 
 l <tkfet ndt/oijty. /he 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 space, 
 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 endeavored 
 to avoid offering such violence to our language, by speaking of the com- 
 ponent materials of the earth as consisting of rocks and soils. But there 
 is often so insensible a passage from a soft and incoherent state to that 
 of stone, that geologists of all countries have found it indispensable to 
 have one technical term to include both, and in this sense we find roche 
 applied in French, rocca in Italian, andfelsart in German. The beginner, 
 however, must constantly bear in mind, that the term rock by no means 
 implies that a mineral mass is in an indurated or stony condition. 
 
 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 endeavoring briefly to explain to the student how all rocks may be 
 divided into four great classes by reference to their different origin, or, in 
 other words, by reference to the different circumstances and causes by 
 which they have been produced. 
 
 The first two divisions, which will at once be understood as natural, 
 are the aqueous and volcanic, or the products of watery and those of 
 igneous action at or near the surface. 
 
 Aqueous rocks. The aqueous rocks, sometimes called the sedimentary, 
 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 the land during temporary inundations. 
 
CH. I.] AQUEOUS ROCKS. 3 
 
 For, whenever a running stream charged with mud or sand, has its ve- 
 locity 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 frequently 
 find at the bottom a series of deposits, disposed with considerable regu- 
 larity, 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 example, of the layers of sand, clay, or 
 marl, may be wanting, one or more of them having thinned out and 
 given place to others, or sometimes one of the masses first examined is 
 observed to increase in thickness to the exclusion of other beds. 
 
 The term "formation" which I have used in the above explanation, 
 expresses in geology any assemblage of rocks which have some character 
 in common, whether of origin, age, or composition. Thus we speak of 
 stratified and unstratified, freshwater and marine, aqueous and volcanic, 
 ancient and modern, metalliferous and non-metalliferous formations. 
 
 In the estuaries of large rivers, such as the Ganges and the Mississippi, 
 we may observe, at low water, phenomena analogous to those of the 
 drained lakes above mentioned, but on a grander scale, and extending 
 over areas several hundred miles in length and breadth. When the pe- 
 riodical 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 color, or in the fineness or coarseness of their 
 particles, and some of them are occasionally characterized by containing 
 drift-wood. At the junction of the river and the sea, especially in la- 
 goons 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 color from 
 that of a previous year, and being separable from it, as has been observed 
 in excavations at Cairo, and other places.* 
 
 When beds of sand, clay, and marl, containing shells and vegetable 
 matter, are found arranged in a similar manner in the interior of the 
 earth, we ascribe to them a similar origin ; and the more we examine 
 their characters in minute detail, the more exact do we find the resem- 
 blance. Thus, for example, at various heights and depths in the earth, 
 and often far from seas, lakes, and rivers, we meet with layers of rounded 
 
 * See Principles of Geology, by the Author, Index, "Nile," " Eiv-ers," <tc. 
 
4 AQUEOUS ROCKS. [Ca. 1. 
 
 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 sedi- 
 ment, 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 originated 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, frag- 
 ments of wood, impressions of leaves, and other organic substances. Fossil 
 shells, of forms such as now abound in the sea, are met with far inland, 
 both near the surface, and at great depths below it. They occur at all 
 heights above the level of the ocean, having been observed at elevations 
 of more than 8000 feet in the Pyrenees, 10,000 in the Alps, 13,000 in 
 the Andes, and above 18,000 feet in the Himalaya.! 
 
 These shells belong mostly to marine testacea, but in some places 
 exclusively to forms characteristic of lakes and rivers. Hence it is con- 
 cluded 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 intermixed ; but the strata containing 
 fossils are not superficial deposits, 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 favorite 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 have been 
 deposited in the bed of the ocean during the period which intervened 
 
 See p. 18, fig. 7. 
 
 f Capt. R. J. Strachey found oolitic fossils 18,400 feet high in the Himalaya. 
 
CH. I] VOLCANIC ROCKS. 5 
 
 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 revo- 
 lutions 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 se limentary 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 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 con- 
 ceded by the theory above alluded to ; and likewise that no one 
 universal and sudden conversion of sea into land will account for geo- 
 logical appearances. 
 
 We have now pointed out one great class of rocks, which, however 
 they may vary in mineral composition, color, grain, or other characters, 
 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 characterized by stratification or 
 fossils, or by both. 
 
 Volcanic rocks. The division of rocks which we may next consider 
 are the volcanic, or those which have been produced at or near the sur- 
 face 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 unstrat- 
 ified, and are devoid of fossils. They are more partially distributed than 
 aqueous formations, at least in respect to horizontal 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 Au- 
 vergne, Velay, and Vivarais, now the departments of Puy de Dome, 
 Haute Loire, and Ard6che, towards the centre and south of France, in 
 which are several hundred conical hills having the forms of modern vol- 
 canoes, with craters more or less perfect on many of their summits. These 
 cones are composed moreover of lava, sand, and ashes, similar to those 
 
6 VOLCANIC ROCKS. [CH, 1 
 
 of active volcanoes. Streams of lava may sometimes be tiaced 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. Al- 
 though none of these French volcanoes have been in activity within the 
 period of history or tradition, their forms are often very perfect. Some, 
 however, have been compared to the mere skeletons of volcanoes, the 
 rains and torrents having washed their sides, and removed all the loose 
 sand and scoriae, leaving only the harder and more solid materials. By 
 this erosion, and by earthquakes, their internal structure 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 scoriae, 
 but also perpendicular walls, or dikes, as they are called, of vo'canic 
 rock, which have burst through the other materials. Such dikes are 
 also observed in the structure of Vesuvius, Etna, and other active 
 volcanoes. They have been formed by the pouring of melted matter, 
 whether from above or below, into open fissures, and they commonly 
 traverse deposits of volcanic tuff, a substance produced by the show- 
 ering down from the air, or incumbent waters, of sand and cinders, 
 first shot up from the interior of the earth by the explosions of volcanic 
 
 Besides the parts of France above alluded to, there are other countries, 
 as the north of Spain, the south of Sicily, the Tuscan territory of Italy, 
 the lower Rhenish provinces, and Hungary, where spent volcanoes may 
 be seen, still 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 Giants' 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 volcanoes. 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 super- 
 ficial lava, in England and many other countries, is principally to be 
 attributed to the eruptions having been submarine, just as a considerable 
 proportion of volcanoes in our own times burst out beneath the sea. 
 But this question must be enlarged upon more fully in the chapters on 
 Igneous Rocks, in which it will also be shown, that as different sedi- 
 mentary formations, containing each their characteristic fossils, have 
 been deposited at successive periods, so also volcanic sand and scoria? 
 
Ce. I] PLUTONIC ROCKS. 7 
 
 have been thrown out, and lavas 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 chronologi- 
 cal series of monuments, throwing light on a succession of events in the 
 history of the earth. 
 
 Plutonic rocks (Granite, &c.). We have now pointed out the exist- 
 ence 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 deposits 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 plutonic, comprehending 
 all the granites and certain porphyries, which are nearly jrilied 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 consti- 
 tute 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 volcanoes, they have been melted, and have 
 afterwards cooled and crystallized, but with extreme slowness, and under 
 conditions very different from those of bodies cooling in the open air. 
 Hence they differ from the volcanic rocks, not only by their more crys- 
 talline 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 cel- 
 lular 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 overflowed. But 
 as this is continually the case with the volcanic rocks, they have 
 been styled, from this peculiarity, " overlying" by Dr. MacCulloch ; 
 
3 METAMOEPHIC ROCKS. [Ca 1 
 
 and Mr. Necker has proposed the term " underlying" for the granites, 
 to designate the opposite mode in which they almost invariably present 
 themselves. 
 
 Metamorphic, or stratified crystalline rocks. The fourth and last 
 great division of rocks are the crystalline strata and slates, or schists, 
 called gneiss, mica-schist, clay-slate, chlorite-schist, marble, and the like, 
 the origin of which is more doubtful than that of the other three 
 classes. They contain no pebbles, or sand, or scoriae, or angular pieces 
 of imbedded stone, and no traces of organic bodies, and they are often 
 as crystalline as granite, yet are divided into beds, corresponding in 
 form and arrangement to those of sedimentary formations, and are 
 therefore said to be stratified. The beds sometimes consist of an alter- 
 nation of substances varying in color, composition, and thickness, pre- 
 cisely as we see in stratified fossiliferous deposits. According to the 
 Huttonian theory, which I adopt as the most probable, and which will be 
 afterwards more fully explained, the materials of these strata were origi- 
 nally 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 laving exchanged an earthy for 
 a highly crystalline texture for a distance of a quarter of a mile from their 
 contact with granite. In some cases, dark limestones replete with shells and 
 corals, have been turned into white statuary marble, and hard clays, contain- 
 ing vegetable or other remains, into slates called mica-schist or hornblende- 
 schist, every vestige of the organic bodies having been obliterated. 
 
 Although we are in a great degree ignorant of the precise nature of 
 the influence exerted in these cases, yet it evidently bears some analogy 
 to that which volcanic heat and gases are known to produce ; and the 
 action may be conveniently called plutonic, because it appears to have 
 been developed in those regions where plutonic rocks are generated, and 
 under similar circumstances of pressure and depth in the earth. Whether 
 hot water or steam permeating stratified masses, or electricity, or any 
 other causes have cooperated to produce the crystalline texture, may be 
 matter of speculation, but it is clear that the plutonic influence has some- 
 times pervaded entire mountain masses of strata. 
 
 In accordance with the hypothesis above 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 juosra, meta, trans, and fAopptj, 
 morphe,/oma. 
 
 Hence there are four great classes of rocks considered in reference to their 
 origin, the aqueous, the volcanic, the plutonic, and the metamorphic. lu 
 the course of this work it will be shown, that portions of each of these four 
 distinct classes have originated at many successive periods. They have all 
 been produced contemporaneously, and may even now be in the progress 
 of formation on a large scale. It is not true, as was formerly supposed, 
 that all granites, together with the crystalline or metamorphic strata, 
 were first formed, and therefore entitled to be called " primitive," and 
 
CH. I] FOUK CLASSES OP KOCKS COXTEMPOKANEOUS. 9 
 
 that the aqueous and volcanic rocks were afterwards superimposed, and 
 should, therefore, 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 natu- 
 rally 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 fossllif- 
 erous, 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 con- 
 stantly 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 subjacent 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 be- 
 longing to one great family, whether they be stratified or unstratified, 
 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 second- 
 ary, 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 pecu- 
 liarity equally attributable 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 unal- 
 tered sedimentary strata. I proposed in the Principles of Geology (first 
 edition, vol. iii.), the term " hypogene" for this purpose, derived from 
 utfo, under, and yivofxai, to be, or to be born / a word implying the 
 theory that granite, gneiss, and the other crystalline formations are alike 
 nether-formed rocks, or rocks which have not assumed their present 
 /orm 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 comparatively 
 modern date, belonging, for example, to the period hereafter to be 
 described as tertiary, they are still underlying rocks. They never repose 
 
10 COMPONENTS OF STKATA. [Cir. II 
 
 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 de- 
 riving their origin from particular causes, and having a certain composi- 
 tion, form, and position in the earth's crust, or other characters both 
 positive and negative, such as the presence or absence of organic re- 
 mains. In the second place, the rocks of each class may be viewed as 
 a grand chronological series of monuments, 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 Diag- 
 onal 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 appear- 
 ance, position, mode of origin, organic contents, and other characters 
 which belong to them as aqueous formations, independently of their age, 
 and we may afterwards consider them chronologically or with reference 
 to the successive geological periods when they originated. 
 
 I have already given an outline of the data which led to the belid 
 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 calcareous, 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 ; 
 
CH. II.] MINERAL COMPOSITION OF STRATIFIED ROCKS. 11 
 
 and, lastly, the calcareous rocks or limestones consist of carbonic acid 
 and lime. 
 
 Arenaceous or siliceous rocks. To speak first of the sandy division : 
 beds of loose sand are frequently met with, of which the grains consist 
 entirely of silex, which term comprehends all purely siliceous minerals, 
 as quartz and common flint. Quartz is silex in its purest form ; flint 
 usually contains some admixture of 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 to- 
 gether 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 ar- 
 ranged in layers parallel to the planes of stratification, 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 sufficient 
 ductility, when kneaded up with water, to be fashioned like paste by 
 the hand, or by the potter's lathe, is called a clay ; and such clays vary 
 greatly in their composition, and are, in general, nothing more than mud 
 derived from the decomposition or wearing down of rocks. The purest 
 clay found in nature is 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 pe- 
 culiar, earthy odor 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 
 
 * The kaolin of China consists of Tl'15 parts of silex, 15'86 of alumine, T92 of 
 lime, and 6'?3 of water (W. Phillips, Mineralogy, p. 33) ; but other porcelain clays 
 differ materially, that of Cornwall being composed, according to Boase, of nearly 
 equal parts of silica and alumine, with 1 per cent, of magnesia. (Phil. Mag. voL 
 x. 1837.) 
 
 f See W. Phillips's Mineralogy, " Alumine." 
 
12 MINERAL COMPOSITION OF STRATIFIED ROCKS. [On. 11 
 
 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 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 ap- 
 plied to a rock in which the grains are partly calcareous and partly sili- 
 ceous, 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 concentric 
 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 resembling 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 mu- 
 riatic acids, or strong vinegar ; for the lime, having a greater chemical 
 affinity for any one of these acids than for the carbonic, unites imme- 
 diately with them to form new compounds, thereby becoming a sulphate, 
 nitrate, or muriate of lime. The carbonic acid, when thus liberated 
 from its union with the lime, escapes in a gaseous form, and froths up 
 or effervesces as it makes its way in small bubbles through the drop ot 
 liquid. This effervescence is brisk or feeble in proportion as the lime- 
 stone is pure or impure, or, in other words, according to the quantity of 
 foreign matter mixed with the carbonate of lime. Without the aid ot 
 this test, the most experienced eye cannot always detect the presence ol 
 carbonate of lime in rocks. 
 
 The above-mentioned three classes of rocks, the siliceous, argillaceous, 
 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 Fontaine- 
 
CH. II.J FOBMS OF STRATIFICATION. 13 
 
 bleau, used for pavement in France. More commonly we find sand and 
 clay, or clay and marl, intermixed in tne same mass. When the sand 
 and clay are each in considerable quantity, the mixture is called loam. 
 If there is much calcareous matter in clay it is called marl ; but this 
 term has unfortunately been used so vaguely, as often to be very ambig- 
 uous. 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 with 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 oc- 
 currence. 
 
 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 color ; but it varies greatly in min- 
 eralogical character, passing from an earthy state to a white compact 
 stone of great hardness. Dolomite, so common in many parts of Ger- 
 many and France, is also a variety of magnesian limestone, usually of a 
 granular texture. 
 
 G-ypsum. 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. Anhydrous gvpsum is a rare vari- 
 ety, 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 color, and below these, layers of shale and sand- 
 stone or beds of shale, divisible into leaf-like laminae, and containing 
 
14 ALTERNATIONS. [Cfl. II 
 
 beautiful impressions of plants. Then again we meet with beds of pure 
 and impure coal, alternating with shales and sandstones, and underneath 
 the whole, perhaps, are calcareous strata, or beds of limestone, filled with 
 corals and marine shells, each bed distinguishable from another by cer- 
 tain fossils, or by the abundance of particular species of shells or 
 zoophytes. 
 
 This alternation of different kinds of rock produces the most distinct 
 stratification ; and we often find beds of limestone and marl, conglom- 
 erate 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, color, and grain, according to 
 the seasons ; the waters are sometimes flooded and rapid, at other periods 
 low and feeble ; different tributaries, also, draining peculiar countries and 
 soils, and therefore charged with peculiar sediment, are swollen at distinct 
 periods. It was also shown that the waves of the sea and currents un- 
 dermine 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 tile 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 Brittany, at the mouth of the Loire. The sur- 
 rounding 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 micaceous 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 distinct mica- 
 ceous lamina. The mica is the heavier mineral of the two ; but it re- 
 mains 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 
 
 * Consult Index to Principles of Geology, " Stratification," "Currents," 
 Deltas," "Water," &c. 
 
CH. II] HORIZONTALI'LT OF STRATA." 15 
 
 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 
 under surfaces of strata, or the planes of stratification, are parallel. 
 Although this is not strictly true, they make an approach to paral- 
 lelism, 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 position 
 arises principally from the motion of the water, which forces along par- 
 ticles 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 depressions where the water is 
 deepest. 
 
 A good illustration of the principle here alluded to may be sometimes 
 seen in the neighborhood of a volcano, when a section, whether natural 
 or artificial, has laid open to view a succession of various-colored layers 
 of sand and ashes, which have fallen in showers upon uneven ground. 
 Thus let A B (fig. 1) be two ridges with an intervening valley. These 
 original inequalities of the surface have been gradually effaced by beds 
 of sand and ashes c, c?, e, the surface at e being quite level. It will be 
 seen that although the materials of the first layers have accommodated 
 
 themselves in a great degree to the shape 
 of the ground A B, yet each bed is thick- 
 est 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 sup- 
 posing 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 
 
16 
 
 DIAGONAL OR CKOS6 STRATIFICATION. 
 
 [On. 11. 
 
 water more than a third of the weight which they have in air, the spe- 
 cific 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. 
 
 Yet, however uniform and horizontal may be the surface of new de- 
 posits 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 distance of many 
 hundred yards continuously ; but we generally find at length that each 
 individual stratum thins out, and allows the beds which were previously 
 above and below it to meet. If the 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 phenomenon 
 of frequent occurrence. We find a series of larger strata, each of which 
 is composed of a number of minor layers placed obliquely to the general 
 
 Fig. 3. 
 
 Section of sand at Sandy Hill, near Biggleswade, Bedfordshire. 
 Height 20 feet. (Green-sand formation.) 
 
 planes of stratification. To this diagonal arrangement the name ol 
 "false or cross stratification" has been given. Thus in the annexed sec- 
 tion (fig. 3) we see seven or eight large beds of loose sand, yellow and 
 
CH. IL] 
 
 CAUSES OF DIAGONAL STRATIFICATION. 
 
 17 
 
 brown, and the lines a, 6, c, mark some of the principal planes of strati- 
 fication, which are nearly horizontal: But the greater part of the sub- 
 ordinate 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 deviation from parallelism of the slanting laminae can- 
 not possibly be accounted for by any rearrangement of the particles ac- 
 quired during the consolidation of the rock. In what manner then can 
 such irregularities be due to original deposition ? We must suppose 
 that at the bottom of the sea, as well as in the beds of rivers, the mo- 
 tions of waves, currents, and eddies often cause mud, sand, and gravel 
 to be thrown down in heaps on particular spots, instead of being spread 
 out uniformly over a wide area. Sometimes, when banks are thus 
 formed, currents may cut passages through them, just as a river forms 
 its bed. Suppose the bank A (fig. 4) to be thus formed with a steep 
 
 Fi.4 
 
 C D 
 
 sloping side, and the water being in a tranquil state, the layer of sedi- 
 ment 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 ve- 
 locity, 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, and on which the nearly 
 
 Fig. 5. 
 
 horizontal layers, 9, 10, 11, may then accumulate. It was shown in fig. 
 3 that the diagonal layers of successive strata may sometimes have an 
 opposite slope. This is well seen in some cliffs of loose 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 thickness of an inch, are 
 composed of quartzose grains. This 
 arrangement may have been due to 
 the altered direction of the tides and 
 
 Cliff between Mismer and Dnnwich. currents ill the same place. 
 
18 CAUSES OF DIAGONAL STRATIFICATION. [Ca. II 
 
 The description above given of the slanting position of the minoi 
 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 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, in- 
 tervene between the shore and the mountains, as in the annexed fig. (7), 
 where a vast succession of slanting beds of gravel and sand may bo 
 
 Monte Calvo. Fig. T. 
 
 Section from Monte Calvo to tho sea by the valley of Magnan, near Nice. 
 A. Dolomite and sandstone. (Green-sand formation ?) 
 a, &, d. Beds of gravel and sand. 
 c. Fine marl and sand of St. Madeleine, with marine shells. 
 
 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 sub- 
 side, 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 ac- 
 
Cn. IL] RIPPLE MARK. 19 
 
 cumulation 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 currents of moderate velocity. By 
 inattention to facts and inferences of this kind, a very exaggerated esti- 
 mate has sometimes been made of the supposed depth of the ancient 
 ocean. There can be no doubt, for example, that the strata a, fig. 7, 
 or those nearest to Monte Calvo, are older than those indicated by 6, 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 conclude, 
 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 can- 
 not 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 neighborhood. That the beds, a, 6, c, c?, are of compara- 
 tively modern date is proved by this fact, that in seams of loamy marl 
 intervening between the pebbly beds are fossil shells, half of which be- 
 long to species now living in the Mediterranean. 
 
 fiipple mark. The ripple mark, so common on the surface of sand- 
 stones of all ages (see fig. 8), and which is so often seen on the sea-shore 
 
 Fig. 8. 
 
 Slab of ripple-marked (new red) sandstone from Cheshire 
 
20 RIPPLE MARE. [Cii. II 
 
 at low tide, seems to originate in the drifting of materials along the 
 bottom of the water, in a manner very similar to that which may explain 
 the inclined layers above described. This ripple is not entirely confined 
 to the beach between high and low water mark, but is also produced on 
 sands which are constantly covered by water. Similar undulating ridges 
 and furrows may also be 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 neighboring dunes, so as to cover the shore, and whiten a dark 
 level surface of sandy mud, and this fresh covering of sand was beauti- 
 fully 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 appear- 
 ance 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 5, c t d, e ; the windward- 
 side a gentle slope, as a, 6, c, c?, fig. 9. When a gust of wind blew 
 
 Fig. 9. 
 
 with sufficient force to drive along a cloud of sand, all the ridges were 
 seen to be in 'motion at once, 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, ac- 
 cording to their shape and momentum, 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 aug- 
 mented. 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 com 
 mon, and two of which are seen in the slab, fig. 8. We may observe 
 this configuration 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 ehange 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 
 
CH. IH] GKADUAL DEPOSITION INDICATED BY FOSSILS. 21 
 
 storms extends to a very slight depth. To this rule, however, there are 
 some exceptions, and recent ripple-marks have been observed at the depth 
 of 60 or 70 feet. It has also been ascertained that currents or large 
 bodies of water in motion may disturb mud and sand at the depth of 300 
 or even 450 feet.* Beach ripple, however, may usually be distinguished 
 from current ripple by frequent changes in its direction. In a slab of 
 sandstone, not more than an inch thick, the furrows or ridges of an an- 
 cient ripple may often be seen in several successive laminae to run to- 
 wards 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 in- 
 fusoria Chalk derived principally from organic bodies Distinction of fresh- 
 water from marine formations Genera of freshwater and land shells Rules 
 for recognizing marine testacea Gyrogonite and chara Freshwater hshes 
 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 remains are 
 distributed through stratified deposits. We should often be unable to 
 detect any signs of stratification or of successive deposition, 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 bot- 
 tom ; 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 ani- 
 mals 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 
 
 e Edin. New PhiL Journ. vol. xxxi.; and Darwin, Vole. Islands, p. 134. 
 
22 
 
 GKADUAL DEPOSITION 
 
 [On. III. 
 
 almost exclusively of corals, and in many cases ii is evident that the present 
 position of each fossil zoophyte has been determined by the manner in 
 which it grew originally. The axis of the coral, for example, if its nat- 
 ural growth is erect, still remains at right angles to the plane of stratifi- 
 cation. If the stratum be now horizontal, the round spherical heads of 
 certain species continue uppermost, and their points of attachment are 
 directed downwards. This arrangement is sometimes repeated through- 
 out 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 tur- 
 bid water. 
 
 In like manner, when we see thousands of full-grown shells dispersed 
 everywhere 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 remains now adhere to it, grew from an embryo to a 
 mature state. Attached shells which are merely external, like some of the 
 serpulae (a) in the annexed figure (fig. 10), may often have grown upon 
 Fi & 10. an oyster or other shell while the an- 
 
 imal 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 interior, one of them exactly 
 on the place where the adductor mus- 
 cle of the Gryphcea (a kind of oys- 
 ter) was fixed. 
 
 Some fossil shells, even if simply 
 attached to the outside of others, bear 
 full testimony to the conclusion 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 
 
 ro58 " 
 
 e ute " i8 
 
CH. III.] 
 
 INDICATED BY FOSSILS. 
 
 23 
 
 illustration. It is well known that these animals, when living, are inva- 
 riably covered with numerous suckers, or gelatinous tubes, called " ambu- 
 lacral," 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 
 
 Fig. 11. 
 
 Serpula attached to 
 
 a fossil Spatangus 
 
 from the chalk. 
 
 Recent Spatangus with the spines 
 removed from one side. 
 
 6. Spine and tubercles, nat size, 
 a. The same magnified. 
 
 one-half of its shell stripped of the spines. In fig. 1 1 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 bris- 
 tles. 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, 
 Fig. is. a genus of bivalve mpllusca. The upper valve (6, fig. 
 
 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 
 a. Echinus from the young Crania adhered to the bared shell, grew and 
 vafve'ofthe Crania P^hed in its turn ; after which the upper valve was 
 attached. separated from the lower before the ^Echinus became 
 
 Z>. Upper valve of tba * 
 
 Crania detached, enveloped in chalky mud. 
 
 It may be well to mention one more illustration of the manner in 
 which single fossils may sometimes throw light on a former state of 
 things, both in the bed of the ocean and on some adjoining land. We 
 meet with many fragments of wood bored by ship-worms, at various 
 depths in the clay on which London is built. 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 mollusk still re- 
 maining in the cylindrical hollows. In fig. 15 e, a representation is 
 given of a piece of recent wood pierced by the Teredo navalis, or com- 
 mon 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 
 
SLOW DEPOSITION OF STEATA. 
 
 [On. IIL 
 
 manner, a piece of fossil wood (a, fig. 14) 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 
 
 Fig. 14. 
 
 Fig. 15. 
 
 Fossil and recent wood drilled by perforating Mollusca. 
 Fig. 14. a. Fossil wood from London clay, bored by Teredina. 
 
 &. Shell and tube of Teredina per sonata, the right-hand figure the ventral, the left the 
 
 dorsal view. 
 Fig. 15. e. Eecent 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. 
 
 on to the valves of the shell (6), which therefore cannot be detached 
 from the tube, like the valves of the recent Teredo. The wood in this 
 fossil specimen is now converted into a stony mass, a mixture of clay 
 and lime ; but it must once have been buoyant and floating in the sea, 
 when the Teredince 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 l-md, enjoying a fit soil and climate. 
 
 I 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 ori- 
 gin was not suspected until of late years, even by naturalists. Great 
 surprise was therefore created by the recent discovery of Professor Ehren- 
 berg of Berlin, that a certain kind of siliceous stone, called tripoli, was 
 entirely composed of millions 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 Diatomacea3 by 
 those naturalists who believe in their vegetable origin. The substance 
 
CH. Ill] 
 
 INFUSORIA OF TRIPOLI. 
 
 25 
 
 alluded to has 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 exam- 
 ined with a powerful microscope, is found to consist of the siliceous 
 plates or frustules of the above-mentioned Diatomacese, united together 
 
 Fig. 16. 
 
 Fig. 17. 
 
 Fig. IS. 
 
 
 Fig. 20. 
 
 Fig. 19. 
 
 D 
 
 EanUaria. GaUonetta GaUoneUa 
 
 vulgaris ? distant, ferruginea. 
 
 These figures are magnified nearly 800 times, except the lower fignre of G. ferruginea (fig. 13 a), 
 which is magnified 2000 times. 
 
 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 Ofaillonella distant (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 Diatomacese are of pure silex, and their forms 
 are various, but very marked and constant in particular genera and spe- 
 cies. Thus, in the family Ba- 
 cillaria (see fig. 16), the fos- 
 sils preserved in tripoli are 
 seen to exhibit the same di- 
 visions and transverse lines 
 which characterize the living 
 species of kindred form. With 
 these, also, the siliceous splen- 
 ic or internal supports of the 
 freshwater sponge, or Spon- 
 gilla of Lamarck, are some- 
 times intermingled (see the 
 needle-shaped bodies in fig. 
 20). These flinty cases and 
 spiculce, although hard, are 
 very fragile, breaking like 
 glass, and are therefore admi- 
 rably adapted, when rubbed, 
 for wearing down into a fine 
 powder fit for polishing the 
 surface of metals. 
 
 Fragment of semi-opal from the great bed of tripoli, Bilin. Besides the tripoli, formed 
 r!| X Th? masmfied. showing circnl.r articula- exclusively of the fossils above 
 
 ies f GaUondla ^ and spicula5 described, there occurs in the 
 
26 FOSSIL INFUSOKIA. [On. Ill 
 
 upper part of the great stratum at Bilin another heavier and more compact 
 stone, a kind of semi-opal, in which innumerable parts of Diatomacece 
 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 Diatomacese have been dissolved by water, and have thus given 
 rise to this opal in which the more durable fossils are preserved like in- 
 sects 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 Sax- 
 ony, the species of DiatomaceaB (or Infusoria, as termed by Ehrenberg) 
 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 innumerable ar- 
 ticulated threads, of a yellow ochre color, composed partly of flint and 
 partly of oxide of iron. These threads are the cases of a minute micro- 
 scopic body, called Gaillonella ferruginea (fig. 18). 
 
 It is clear that much time must have been required for the accumulation 
 of strata to which countless generations of Diatomacea3 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. Lons- 
 dale, on examining, 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 frag- 
 ments 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 smallest of them, such as a, fig. 24, 
 
 Cytheridm and Foraminifera from the chalk. 
 Fig. 21. Fig. 22. Fig. 23. Fig. 24. 
 
 u 
 
 Cythere, Mull. Portion of Cristellaria Rosalina. 
 
 Cytherina, Lam. Nodosaria, rotulata. 
 
 are gigantic in comparison with the cases of Diatomacere before men- 
 tioned. It has, moreover, been lately discovered that the chambers into 
 which these Foraminifera are divided are actually often filled with thou- 
 
CH. in.] FRESHWATER AND MARINE FOSSILS. 27 
 
 sands of well-preserved organic bodies, which abound in every minute 
 grain of chalk, and are especially apparent in the white coaling of 
 flints, often accompanied 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 re- 
 mains, so also many chalk flints in which no organic structure can be 
 recognized may nevertheless have constituted a part of microscopic 
 animalcules. 
 
 " The dust we tread upon was once alive !" BYBON. 
 
 How faint an idea does this exclamation of the poet convey of the 
 real wonders of nature ! for here we discover proofe 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 re- 
 mote, 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 fre- 
 quent lakes and rivers are distinct from those inhabiting the sea. In 
 the northern part of the Isle of Wight formations of marl and lime- 
 stone, more than 50 feet thick, occur, in which the shells are prin- 
 cipally, 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 lime- 
 stone, marl, and sandstone are found, hundreds of feet thick, which con- 
 tain 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, Find- 
 heim, Budenheim, and other places. In order to account for this phe- 
 nomenon, 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 away from 
 the alluvial plains of the great river and its tributaries, some from 
 mountainous regions, others from the low country. 
 
28 
 
 DISTINCTION OF FRESHWATER 
 
 [On. TIL 
 
 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 comparison 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 zoophytes ; no 
 chambered shells, such as the nautilus, nor microscopic Foraminifera. 
 But it is chiefly by attending to the forms of the rnollusca 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 ma- 
 rine. 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, 
 
 Fig. 25. 
 
 Fig. 26. 
 
 Cyclas obotata ; fossil. Ilanta, 
 
 Cyrena consobrina ; fossil. Grays, Essex 
 
 about ten only out of ninety genera being freshwater. Among these 
 last, the four most common forms, both recent and fossil, are Cyclas, Cy- 
 
 Fig. 27. 
 
 Fig. 28. 
 
 Fig. 29. 
 
 Anodonta Cordierii ; 
 fossil. Paris. 
 
 Anodonta latimarginatzis ; 
 recent Bahia. 
 
 Unio littoralis ; 
 recent Auvergne. 
 
 rena, Unio, and Anodonta (see figures) ; the 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. IIL] 
 
 FROM MARIXE FORMATIONS. 
 
 29 
 
 Fig- so. 
 
 Gryphcea incurva, Sow. (G. 
 
 arcuata, Lam.) upper 
 
 valve. Lias. 
 
 ludina. (See figures.) 
 
 Fig. 81. 
 
 Lamarck divided the bivalve mollusca into the 
 Dimyary, or those having two large muscular 
 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 presume a deposit in 
 which we find any of them to be marine. 
 
 The univalve shells most characteristic of fresh- 
 water deposits are, Planorbis, Lymnea, and Pa- 
 But to these are occasionally added Physa, Sue- 
 
 Fig. 32. Fig. 33. 
 
 Planorbis euompTialus ; 
 fossil Isle of Wight 
 
 Lymnea longiscata ; 
 fossil Hants. 
 
 Paludina lento, ; 
 fossil Hants. 
 
 cinea, Ancylus, Valvata, Melanopsis, Melania, and Neritina. (See figures.) 
 
 Fig. 34. Fig. 85. Fig. 36. Fig. 37. 
 
 Succinea amphibia ; 
 fossil. Loess, Ehine. 
 
 Ancylus elegant ; 
 fossil Hants. 
 
 Valvata; 
 
 fossil. 
 Grays, Essex. 
 
 Physa hypnorum ; 
 recent 
 
 In regard to one of these, the Ancylus (fig. 35), Mr. Gray observes 
 that it sometimes differs in no respect from the marine Siphonaria, ex- 
 Fig. 83 Fig. 39. Fig. 40. Fig. 41. 
 
 Auricula ; 
 recent Ava. 
 
 Melania, 
 inquinata. 
 Paris basin. 
 
 Melanopsis "buc- 
 cinoidea; recent 
 Asia. 
 
 cept in the animal. The shell, however, of the Ancylus is usually 
 thinner.* 
 
 * Gray, Phil. Trans. 1835, p. 302. 
 
so 
 
 DISTINCTION OF FEESHWATEE 
 
 [Ce. III. 
 
 Some naturalists include Neritina (fig. 42) and the marine Nerita 
 (fig. 43) in the same genus, it being scarcely possible to distinguish the 
 
 Fig. 42. 
 
 Fig. 43. 
 
 Fig. 44. 
 
 Neritina globulus. Paris basin. 
 
 Nerita granulosa, Paris basin. 
 
 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 JVeritce, 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 spe- Cerituum 
 cies peculiar to each. Other genera, like Auricula (fig. 38), are p^ris 3 basin 
 amphibious, frequenting marshes, especially 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), Cy- 
 dostoma (fig. 46), Pupa (fig. 47), Clausilia (fig. 48), Bulimus (fig. 49), 
 
 Fig. 46. 
 
 Fig. 46. 
 
 Helve, Turonensis. 
 Faluns, Touraine. 
 
 Cyclostoma 
 elegam. 
 
 Fig. 47. Fig. 43. Fig. 49. 
 
 Pupa 
 tridens. 
 Loess. 
 
 Clausilia 
 bidens. 
 Loess. 
 
 Bulimus lubricus. 
 Loess, Khine. 
 
 and Achatina ; which two last are nearly allied and pass into each other. 
 The Ampullaria (fig. 50) is another genus of shells, inhabiting 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 oonchologists to belong to Natica and other ma- 
 rine genera. 
 
 All univalve shells of land and freshwater species, 
 with the exception of Melanopsis (fig. 41), and Acha- 
 
 Amputtaria glauca, 
 from the Jumna. 
 
 Una, which has a slight indentation, have 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 aperture 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, 
 
OH. Ill] FROM MARINE FORMATIONS. 31 
 
 such as that seen at b in Ancillaria (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 ; whereas 
 
 Fig. 51. 
 
 Pleurotoma 
 
 rotata. 
 
 Subap. hills, 
 
 Italy. 
 
 Ancillaria subitlata. Barton clay. 
 
 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 exception 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 
 that 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), in- 
 habit salt water ; and, although the animal differs slightly, the shell is 
 scarcely distinguishable from that of the Cypris. 
 
 The seed-vessels and stems of Cham, 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 Clutrce 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 ex- 
 tinct fossil species found in England, France, and other countries. Tho 
 
 * For figures of fossil species of Purbeck, see below, ch. JOE. 
 
32 
 
 FEESH WATER AND MARINE FORMATIONS. [OH. III. 
 
 stems, as well as the seed-vessels, of these plants occur both in modern 
 shell marl and in ancient freshwater formations. They are generally 
 
 Fig. 53. 
 
 Fig. 54. 
 
 Ohara medieaginula ; 
 fossil. Upper Eocene, 
 Isle of Wight. 
 a. Seed-vessel, 
 
 magnified 20 
 
 diameters. 
 &. Stem, magnified. 
 
 Chara elasUca ; recent Italy. 
 
 a. Sessile seed-vessel between the divisions of 
 the leaves of the female plant. 
 
 &. Magnified transverse section of a branch, 
 with five seed-vessels, seen from below 
 upwards. 
 
 composed of a large tube surrounded by smaller tubes ; the whole stem 
 being divided at certain intervals by transverse partitions or joints. 
 (See 6, fig. 53.) 
 
 It is not uncommon to meet with layers of vegetable matter, impres- 
 sions of leaves, and branches of trees, in strata containing freshwater 
 shells ; and we also find occasionally the teeth and bones of land quad- 
 rupeds, 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 fresh- 
 water origin of strata. Certain genera, such as carp, perch, pike, and 
 loach ( Cyprinus, Perca, JEsoz, and Cobitis), as also LeUas, being pe- 
 culiar to freshwater. Other genera contain some freshwater and some 
 marine species, as Cottus, 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 observations 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 ex- 
 isting fishes, that it is very difficult, at least in the present state of sci- 
 ence, to derive any positive information from icthyolites respecting the 
 element in which strata were deposited. 
 
 -j- 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 
 helk 
 
 * See Index of Principles, " Fossilization." 
 
CH. IV.] CONSOLIDATION OF STKATA. 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 commu- 
 nicate 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 pe- 
 riods 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 ex- 
 tremity 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 1824, when the North Sea 
 entered, killing all the freshwater shells, fish, and plants ; and from that 
 time to the present, the sea-weed Fucus vesiculosus, together with oys- 
 ters and other marine mollusca, have succeeded the Cyclas, Lymnea, 
 Paludina, and Charce* 
 
 But changes like these in the Lym-Fiord, and those before mentioned 
 as occurring at the mouths of great rivers, will only account for some 
 cases of marine deposits of partial extent resting on freshwater strata. 
 When we find, as in the southeast of England, a great series of fresh- 
 water 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 phenomena.! 
 
 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 consolidation 
 of stratified rocks, and the petrifaction of imbedded organic remains. 
 
 Chemical and mechanical deposits. A distinction has been made by 
 
 * See Principles, Index, " Lym-Fiord." 
 
 f Sec below, Chap. XVIII., on the Wealden. 
 
34 CONSOLIDATION OF STRATA. [On. IV. 
 
 geologists between deposits of a chemical, and those of a mechanical, 
 origin. By the latter name are designated beds of mud, sand, or peb- 
 bles produced by the action of running water, also accumulations 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 precipitated 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, incrusting shells, fragments of 
 wood and leaves, and binding them together.* 
 
 In coral reefs, large masses of limestone are formed by the stony skel- 
 etons of zoophytes ; and these, together with shells, become cemented 
 together by carbonate of lime, part of which is probably furnished to 
 the sea-water by the decomposition of dead corals. Even shells of which 
 the animals are still living, on these reefs, are very commonly found to 
 be incrusted over with a hard coating of limestone.f 
 
 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 hori- 
 zontality 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 incrust the vertical 
 walls of a fissure, and be of equal thickness throughout ; but such de- 
 posits 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 Kelloway 
 in Wiltshire. A peculiar band of sandy strata, belonging to the group 
 called Oolite by geologists, may be traced through several counties, the 
 sand being for the most part loose and unconsolidated, but becoming 
 
 * See Principles, Index, " Calcareous Springs," <fec. 
 \ Ibid. " Travertin," " Coral Reefs," <fec. 
 
Cu. IV.] CONSOLIDATION OF STRATA. 35 
 
 stony near Kelloway. In this district there are numerous 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 sand- 
 stone has been produced. If we take fragments of many other argilla- 
 ceous grits, retaining the casts of shells, and plunge them imto 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 
 
 O 
 
 decomposition as to crumble into powder when touched. It is clear that 
 water percolating such strata may soon remove the calcareous matter of 
 the shell ; and, unless circumstances cause the carbonate of lime to be 
 again deposited, the grains of sand will not be cemented together ; in 
 which case no memorial of the fossil will remain. The absence of or- 
 ganic 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 fragment 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 ex- 
 ample, in the Mediterranean, at the depth of about 230 fathoms, accord- 
 ing to the researches of Prof. E. Forbes. In the ^Egean 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 dif- 
 fused 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 temperature of the solvent is 
 lowered, mineral matter has a tendency to separate from it and solidify. 
 Thus a stony cement is often supplied to sand, pebbles, or any fragment- 
 ary mixture. In some conglomerates, like the pudding-stone of Hertford- 
 shire (a Lower Eocene deposit J, 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 con- 
 firm this idea : by far the greater number of the stones used for building 
 and road-making are much softer when first taken from the quarry 
 than after they have been long exposed to the air ; and these, when once 
 
 * Report Brit. Ass. 1843, p. 178. 
 
36 CONSOLIDATION OF STKATA. [On. IV. 
 
 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 
 themselves deprived of freedom of motion, but would also bind together 
 other portions of the rock which before were loosely aggregated. On 
 the same principle wet sand and mud become as hard as stone when 
 frozen ; because one ingredient of the mass, namely, the water, has crys- 
 tallized, 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 marlstone, like that 
 observed in many ancient European formations, and like them contain- 
 ing 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 artificial mix- 
 ture 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 lime. This substance hardens, and becomes a solid stone in water, 
 and was used by the Romans in constructing the foundations of build- 
 ings 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 successive laminae ; for these laminae 
 
 * Dr. MacCulloch, Syst. of Geol. vol. i. p. 123, 
 
CH. IV.] 
 
 COXCRETTOXARY STRUCTURE. 
 
 37 
 
 Fig. 55. 
 
 Calcareous nodules in Lias. 
 
 Fig, 56. 
 
 
 Spheroidal concretions in magnesian 
 limestone. 
 
 are often traced in the concretions, remaining parallel to those of the sur- 
 rounding 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 exam- 
 ples 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 diameter of several feet, and they have both a con- 
 centric 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 in- 
 stance we must suppose the deposition of 
 a series of minor layers, first forming the 
 stratum 6, 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 inter- 
 fering with the laminated structure of the rock. 
 
 When the particles of rocks have been thus rearranged by chemical 
 forces, it is sometimes difficult or impossible to ascertain whether certain 
 lines of division are due to original deposition or to the subsequent ag- 
 gregation of similar particles. Thus suppose three strata of grit, A, B, 
 
 C, are charged unequally with calcareous 
 matter, and that B is the most calcareous. 
 If consolidation takes place in B, the con- 
 cretionary action may spread upwards 
 into a part of A, where 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 c?, e, being thus effaced, the 
 line d, /, 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 
 
 Fig. 57. 
 
 * De la Beche, Geol. Researches, p. 95, and Geol. Observer (1851), p. 686. 
 
38 MINERALIZATION OF [Cn. IV. 
 
 of fluid above. The same happens in regard to organic remains which 
 are filled with water under great pressure as 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 become 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 mechanical 
 movements afterwards to be described, by which strata have be^n bent, 
 broken, and raised above the level of the sea. Rocks of more yielding 
 materials must often have been forced against others previously consol- 
 idated, 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 powdei 
 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 inetamorphic 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 conch ologist 
 to be the internal shape of the fossil univalve, 6, fig. 58. Nor should 
 
CH. IV.] ORGANIC REMAINS. 39 
 
 we have imagined at first sight that the shell a and the cast 6, fig. 59, 
 were different parts of the same fossil. The reader will observe, in the 
 
 Fig. 89. 
 
 Pha&ianfUa ffeddingtonenxis, Pleurotom aria A n ylica and 
 
 and cast of the same. Coral Eag. cast Lias. 
 
 last-mentioned figure (6, 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 particles 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 striae, 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, py- 
 rites, or other mineral, we then obtain from the mould an exact cast both 
 of the external and internal form of the original shell. In this manner 
 silicified casts of shells have been formed ; and if the mud or sand of 
 the nucleus happen to be incoherent, or soluble in acid, we can then pro- 
 cure in flint an empty shell, which in shape is the exact counterpart of 
 the original. This cast may be compared to a bronze statue, representing 
 merely the superficial form, 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 anatom- 
 ical models in wax, where not only the outward forms and features, but 
 the nerves, blood-vessels, and other internal organs are also shown. 
 Thus we find corals, originally calcareous, in which not only the general 
 shape, but also the minute and complicated internal organization are re- 
 tained 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 cells and fibres of plants, and even those spiral vessels which in 
 the living vegetable can only be discovered by the microscope, are pre- 
 served. 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, the texture seen in fig. 60 is ex- 
 
4.0 MINEEALIZATIOX OF [On. IV. 
 
 hibited. A texture equally minute and complicated has been observed 
 in the wood of large 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 parallel 
 rows of vessels here seen are the rings of an- 
 nual growth, but in one part they are imperfectly 
 T7x7ure~o7a treT^m'the Preserved, the wood having probably decayed 
 coal strata, magnified. (Wi- before the mineralizing; matter had penetrated to 
 
 tham.) Transverse section. 
 
 that portion ot 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 after- 
 wards 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 de- 
 compose 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 min- 
 eral, is at hand and ready to be precipitated, we may imagine this inor- 
 ganic 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 
 colored at different times, or so crystallized as to reflect light differ- 
 ently, 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 Gop- 
 pert of Breslau attempted recently to imitate the natural process of pet- 
 rifaction. 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 sylvestris), were immersed in a moderately 
 
Ca IV.] ORGANIC REMAINS. 41 
 
 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 fam- 
 ily 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 discovered the bones of several mice 
 in a sediment consisting of small grains of pyrites, others of sulphur, 
 others of crystallized green sulphate 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 ox- 
 ygen ; hence the pyrites and the other compounds were thrown down. 
 Although the mice were not mineralized, or turned into pyrites, the phe- 
 nomenon shows how mineral waters, charged with sulphate of iron, may 
 be deoxydated on coming in contact with animal matter undergoing pu- 
 trefaction, so that atom after atom of pyrites may be precipitated, and 
 ready, under favorable 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 immersed by Professor Goppert in various 
 fluid mixtures. 
 
 Tt is well known that the water of springs, or that which is continually 
 
 * Vol. i. p. 399, first series. 
 
 \ Piddington, Asiat, Research, vol. xviii. p. 226. 
 
4:2 FLINT OF SILICIFIED FOSSILS. [On. IV. 
 
 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 ; and 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 decomposition of diatomaceae, sponges, and othei 
 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 decomposing, may be- 
 come so charged with carbonic acid as to acquire a power of dis- 
 solving 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 ex- 
 plained, in an essay on the chemistry of geology,* how the decomposi- 
 tion of felspar may be a source of silex in solution. He has remarked 
 that the siliceous earth, which constitutes 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 carbonic 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 residue 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 dis- 
 solved and removed ; and this can be accounted for in two ways ; first, 
 because silica when combined with an alkali is soluble in water ; sec- 
 ondly, 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 felspathic rocks are universally dis- 
 tributed, constituting, as they do, so large a proportion of the volcanic, 
 plutonic, and metamorphic formations. Even where they chance to be 
 absent in mass, they rarely fail to occur in the superficial gravel or allu- 
 vial deposits of the basin of every large river. 
 
 The disintegration of mica also, another mineral which enters largely in- 
 to the composition of granite and various sandstones, may 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 ox- 
 idation of this iron in the air is the principal cause of the waste of mica. 
 
 * Jam. Ed. New Phil. Journ. No. 30, p. 246. 
 
Cn. IV.] PKOCESS OF PETRIFACTION. 43 
 
 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 silicifica- 
 tion 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 re- 
 tarded putrefaction, so that the soft parts of the buried substance may 
 have remained for a long time without disintegration, 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 de- 
 pended on the time when the lapidifying mineral was introduced. Thus, 
 in certain silicified stems of palm-trees, the cellular tissue, that most de- 
 structible 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 commenced soon after 
 the wood was exposed to the action of moisture, and the supply of min- 
 eral 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 be- 
 fore the commencement of lapidification, during which the cellular tissue 
 was obliterated. When both structures, 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.f 
 
 * 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 
 extensive masses of horizontal strata Inclined and vertical stratification An- 
 ticlinal and synclinal lines Bent strata in east of Scotland Theory of folding 
 by lateral movement Creeps Dip and strike Structure of the Jura Vari- 
 ous forms of outcrop Rocks broken by flexure Inverted position of disturbed 
 strata Unconformable stratification Hutton and Playfair on the same Frac- 
 tures of strata Polished surfaces Faults Appearance of repeated alterna- 
 tions 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 conti- 
 nental 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 the 
 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 sat- 
 isfactory 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 re- 
 peatedly moved upwards or downwards, so as permanently to change ita 
 
OH. V.] NOT THE SEA LOWERED. 45 
 
 position relatively to the sea. There are several distinct grounds for 
 preferring this conclusion. First, it will account equally for the position 
 of those elevated masses of marine origin in which the stratification re- 
 mains 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 con- 
 vulsions, while in others they have proceeded 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 evi- 
 dence 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 Mediter- 
 ranean. 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 strata 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 geologists, 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 Mountain at the Cape of Good Hope is another example of highly 
 elevated yet perfectly horizontal strata, no less than 3500 feet in thick- 
 ness, 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, how- 
 ever 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. Play- 
 fair argued in favor of this opinion in 1802 ; and in 1807, Yon Buch, 
 after his travels in Scandinavia, announced his conviction that a rising 
 of the land was in progress. Celsius and other Swedish writers had, 
 
46 RISING- AND SINKING OF LAND. [On. V. 
 
 a century before, declared their belief that a gradual change had, for 
 ages, been taking place in the relative level of land and sea. They at- 
 tributed the change to a fall of the waters both of the ocean and the 
 Baltic. This theory, however, has now been refuted by abundant evi- 
 dence ; 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 south- 
 ernmost part of Sweden, or the province of Scania, there has been actu- 
 ally 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 under- 
 going 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 evi- 
 dence has been daily strengthened of continued changes of level effected 
 by violent convulsions in countries where earthquakes are frequent. There 
 the rocks are rent from time to time, and heaved up or thrown down 
 several feet at once, and disturbed in such a manner, 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 cir- 
 cular coral islands and barrier reefs abound, there is a slow and continued 
 sinking of the submarine mountains on which the masses of coral are 
 based ; while there are other areas of the South Sea, where the land is 
 on the rise, and where coral has been upheaved far above the sea-level. 
 
 It would require a volume to explain to the reader the various facts 
 which establish the reality of these movements of land, whether of ele- 
 vation or depression, whether accompanied by earthquakes or accom- 
 plished 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 horizon- 
 tal, inclined, or disturbed marine strata, and the superposition of fresh- 
 
 * In the first three editions of my Principles of Geology, I expressed many 
 doubts as to the validity of the alleged proofs of a gradual rise of land in Sweden ; 
 but after visiting that country, in 1834, I retracted these objections, and published 
 a detailed statement of the observations which led me to alter my opinion in the 
 Phil. Trans. 1835, Part I. See also the Principles, 4th and subsequent editions. 
 
 f See his Journal of a Naturalist in Voyage of the Beagle, and his work on 
 Coral Reefs. 
 
 \ See chapters xxvii. to xxxii. inclusive, and chap. 1. 
 
CH. V.J 
 
 INCLINED STRATIFICATION. 
 
 47 
 
 Fig. 61. 
 
 water to marine deposits, afterwards to be described. It will also appear, 
 in the sequel, how much light the doctrine of a continued subsidence of 
 land may throw on the manner in which a series of strata, formed in 
 shallow water, may have accumulated to a great thickness. The exca- 
 vation 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 oscillations 
 in the level of the waters instead of the land, we should be compelled to 
 admit that the ocean has been sometimes everywhere 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 perpen- 
 dicularly on their edges, which is by no means a rare phenomenon, es- 
 pecially in mountainous countries. Thus we find in Scotland, on the 
 southern skirts of the Grampians, beds of pudding-stone alternating 
 with thin layers of fine sand, all placed vertically to the horizon. When 
 Saussure first observed certain conglomer- 
 ates in a similar position in the Swiss Alps, 
 he remarked that the pebbles, being for the 
 most part of an oval shape, had their 
 longer axes parallel to the planes of strati- 
 fication (see fig. 61). From this he in- 
 ferred, that such strata must, at first, have 
 been horizontal, each oval 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, in- 
 deed, 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 twenty 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 thickness, 
 consisting of red and white sandstone, and various colored shales, the 
 beds being distinguishable into four principal groups, namely, No. l,red 
 marl or shale ; No. 2, red sandstone, used for building ; No. 3, conglom- 
 erate ; and No. 4, gray paving-stone, and tile-stone, with green and red- 
 
 Vertical conglomerate and sandstone. 
 
CUKVED STKATA. 
 
 [OH. V. 
 
 E* 
 
 ll 
 
 1 
 
 dish shale, containing peculiar organic re- 
 J mains. A glance at the section will show 
 'Q that each of the formations 2, 3, 4, are re- 
 peated thrice at the surface, twice with a 
 2 southerly, and once with a northerly incli- 
 g* cation or dip, and the beds in No. 1, which 
 S are nearly horizontal, are still brought up 
 'g twice by a slight curvature to the surface, 
 f once on each side of A. Beginning at the 
 2" northwest extremity, the tile-stones and 
 2 conglomerates No. 4 and No. 3 are verti- 
 % cal, and they generally form a ridge par- 
 allel to the southern skirts of the Grampi- 
 | ans. The superior strata Nos. 2 and 1 be- 
 5 1 come less and less inclined on descending 
 g-g to the valley of Strathmore, where the 
 || strata, having a concave bend, are said by 
 a - * 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 trav- 
 elling from the north to the centre of the 
 basin, he is always passing from older to 
 newer beds; whereas, after crossing the 
 line A, and pursuing his course in the same 
 southerly direction, he is continually leav- 
 ing the newer, and advancing upon older 
 strata. All the deposits which he had be- 
 fore examined begin then to recur in re- 
 versed 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 White- 
 ness (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 conglom- 
 erate and sand, and are newer than any of the groups, 1, 2, 3, 4, before de- 
 scribed, and rest unconformaUy 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. Abb's Head, 
 * Edin. Trans, vol. vii. pi. 3. 
 
CH. V.] EXPERIMENTS TO ILLUSTRATE CURVED STRATA. 
 
 49 
 
 on the east coast of Scotland, where the rocks consist principally of a 
 bluish slate, having frequently a ripple-marked surface. The undulations 
 of the beds reach from the top to the bottom of cliffs from 200 to 300 
 
 Fig. 63. 
 
 Curved strata of slate near St. Abb's Head, Berwickshire. (Sir J. Hall.) 
 
 feet in height, and there are sixteen distinct bendings in the course of 
 about six miles, the curvatures being alternately concave and convex up- 
 wards. 
 
 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 opposite ends 
 pressed towards each other with such force as to cause them to approach 
 more nearly together. On the removal of the weight, the layers of clay 
 were found to be curved and folded, so as to bear a miniature resemblance 
 to the strata in the cliffs. We must, however, bear in mind, that in the 
 natural section or sea-cliff we only see the 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 
 
 Fig. 64 
 
 water which will be explained in the next chapter. The dark lines m 
 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 por- 
 
 4 
 
50 CURVED STRATA. [Ca V. 
 
 tion which is concealed beneath the sea-level, as also that which is sup- 
 posed 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 differently 
 colored cloths upon a table, and when they are spread out horizontally, 
 
 Fig. 65. 
 
 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 difficulty. 
 It will appear when the volcanic and granitic rocks are described, that 
 some of them have, when melted, been injected forcibly into fissures, 
 while others, already in a solid state, have been protruded upwards 
 through the incumbent crust of the earth, by which a great displace- 
 ment 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 sometimes extend- 
 ing over a wide area. The frequent repetition, or continuance 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 volcanoes and hot springs, or by the contrac- 
 tion of argillaceous rocks by heat and pressure, or any other combination 
 of circumstances. Whatever conjectures we may indulge respecting the 
 causes, it is certain that pliable beds may, in consequence of unequal 
 degrees of subsidence, 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 il 
 lustration of this fact. First, it may be stated generally, that the exca 
 vation of coal at a considerable depth causes the mass of overlying strata 
 to sink down bodily, even when props are left to support the roof of the 
 mine. "In Yorkshire," says Mr. Buddie, "three distinct subsidences 
 were perceptible at the surface, after the clearing out of three seams of 
 coal below, and innumerable vertical cracks were caused in the incum- 
 bent mass of sandstone and shale, which thus settled down."* The ex- 
 
 * Proceedings of Geol. Soc. vol. iii. p. 148. 
 
CH. V.I 
 
 CREEPS IX COAL-MIXES. 
 
 51 
 
 act amount of depression in these cases 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, Newcastle, 
 
 the galleries which have been excavated are represented by the white 
 spaces a 6, while the adjoining dark portions are parts of the original 
 coal-seam left as props, beds of sandy clay or shale constituting the floor 
 of the mine. When the props have been reduced in size, they are pressed 
 
52 CURVED STRATA, [Ce. Y 
 
 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 composed 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 curvature 
 at the bottom of each gallery, as at a, fig. 66 ; then the pavement con- 
 tinuing 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 reunited 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 a, 6, c, d, an inferior 
 stratum, called the " metal coal," which is 3 feet thick, has been fractured 
 at the points e, /, #, 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, whieh 
 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 no- 
 tice 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 curv- 
 ature of the beds is most regular, and the reunion of the fractured ends 
 most complete ; whereas the signs of displacement or violence are great- 
 est 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 when these strata,, including 
 
OH. V.] DIP AND STRIKE. 53 
 
 vegetable remains, are curved again and 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, these zigzag bendings are repeated four 
 
 Fig. 67. 
 
 Zigzag flexures of coal near Mons. 
 
 or five times, in the manner represented in fig. 67, the black lines repre- 
 senting 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 devi- 
 ation from a level or horizontal line is called the amount of dip, or the 
 Fig. 63. angle of dip. Thus, in the annexed 
 
 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 pro- 
 longation or extension of the strata 
 in a direction at right angles to the dip ; and hence it is sometimes called 
 the direction of the strata. Thus, in the above instance of strata dipping 
 to the north, their strike must necessarily be east and west. We have 
 borrowed the word from the German geologists, streichen signifying to 
 extend, to have a certain direction. Dip and strike may be aptly illus- 
 trated 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 endeavoring to com- 
 prehend 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 occa- 
 sionally deceived, both as to the point of dip and the amount of it. 
 
 * See plan by M. Chevalier, Burat's D'Aubuisson, torn, il p. 334. 
 
54 DIP AND STKIKE. [Cu. 7. 
 
 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 which faces to the north, where the 
 
 Fig. 69. 
 
 Apparent horizontally of inclined strata. 
 
 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 endeavor 
 to find a ledge or portion of the plane of one of the beds projecting be- 
 yond 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 standing exactly 
 Fig. 70. 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 perpendicular, and of the other in 
 a horizontal position, as in fig. 70. It is 
 thus easy to discover whether the lines of 
 the inclined 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 divide 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 the compass as in the lower dotted 
 
CH. V.] 
 
 DIP AND STEIKE. 
 
 55 
 
 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 con- 
 cave and convex bendings are occasionally repeated several times. These 
 usually form part of a series of parallel waves of strata, which are pro- 
 longed in the same direction throughout a considerable 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 longi- 
 tudinal valleys, as in fig. 71, the ridges being formed by curved fossilif- 
 erous 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 synclinal line. 
 
 Fig.7t 
 
 Fig. 7-2. 
 
 Fig. 73. 
 
 Section illustrating the structure of the Svriss Jura. 
 
 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 portio i of it carried away by denudation, so that the ridges 
 of the beds in the formations a, 6, c, come out to the day, or, as the 
 
 miners say, crop out, on the sides 
 of a valley. The ground plan of 
 such a denuded ridge as C, as given 
 I in a geological map, may be ex- 
 | 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 of 
 which the dip is in opposite direc- 
 
 Ground plan of the denuded ridg*C, fig. 71. 
 
 * Seo M. Thurmann's work, " Essai sur les Soulevemena Jurassiques du Por- 
 rentruy, Paris, 18S2," with whom I examined part of these mountains in 1835. 
 
56 
 
 OUTCROP OF STRATA. 
 
 [On. V. 
 
 tions, as expressed by the arrows. The emergence of strata at the sur- 
 face is called by miners their outcrop or basset. 
 
 If, instead of being folded into parallel ridges, the beds form a boss 
 or dome-shaped protuberance, and if we suppose the summit of the 
 dome carried off, the ground plan would exhibit the edges of the strata 
 forming a succession of circles, or ellipses, round a common centre. 
 These circles are the lines of strike, and the dip being always at right 
 angles is inclined in the course of the circuit to every point of the com- 
 pass, 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-likc 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 appear- 
 ing 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 down- 
 wards (see fig. 75), and 
 those formed of the older 
 beds will now appear up- 
 permost, 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 incli- 
 nation, the newer beds will 
 appear the highest, as in 
 the first and second cases. 
 This is shown by the draw- 
 ing (fig. 76), which exhib- 
 its strata rising at an angle 
 
 Slope of valley 20, dip of strata 50. of 20, and crossed by 
 
 Fig. 74. 
 
 Slope of valley 40, dip of strata 20. 
 Fig. 75. 
 
CH. V.I 
 
 AXT1CLIXAL AND SYXCLIXAL LIXES. 
 
 57 
 
 Slope of valley 20, dip of strata 20, in opposite 
 directions. 
 
 a valley, which declines in an 
 opposite direction at 20.* 
 
 These rules may often be of 
 great practical utility; for 
 the different degrees of dip 
 occurring in the two cases 
 represented in figures 74 and 
 7 5, may occasionally be en- 
 countered in following the 
 same line of flexure at points 
 a few miles distant from 
 each other. A miner un- 
 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. 7o, and discovering there also the out- 
 crop 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 
 demonstrate the futility of such hopes. 
 
 In the majority of cases, an anticlinal axis forms a ridge, and a syn- 
 clinal axis a valley, as in A, B, fig. 62, p. 48 ; but there are exceptions 
 to this rule, the beds sometimes sloping in- 
 wards from either side of a mountain, 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 en- 
 larged 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 be- 
 neath 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. They may have owed their flexibility in part to the 
 
 * I am indebted to the kindness of T. Sopwith, Esq., for three models which I 
 have copied in the above diagrams ; but the beginner may find it by no means 
 easy to understand such copies, although, if he were to examine and handle the 
 originals, turning them about in different ways, he -would at once comprehend 
 their meaning, as well as the import of others far more complicated, \vhich the 
 same engineer has constructed to illustrate faults. 
 
 Fig. T7. 
 
58 
 
 REVERSED DIP OF STRATA. 
 
 [On. 
 
 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 
 che-t. At certain points, as at a, fig. 78, some of the bendings of the 
 
 Fig. 78. 
 
 Fig. 79. 
 
 Strata of chert, grit, and marl, near St. Jean de Luz. 
 
 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 chalcedony and quartz. 
 
 Between San Caterina and Castrogiovanni, in Sicily, bent and undu- 
 lating gypseous marls occur, with here and there thin beds of solid 
 
 gypsum interstratified. Sometimes these 
 solid layers have been broken into detached 
 fragments, still preserving their sharp edges 
 (ff 9i % *79), while the continuity 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 re- 
 gions 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 them- 
 selves, 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 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 re- 
 peated, the position of one-half being reversed, and part of No. 1, origi- 
 nally the uppermost, having now become the lowest of the series. These 
 phenomena are often observable on a magnificent scale in certain regions 
 in Switzerland in precipices from 2000 to 3000 feet in perpendicular 
 height. In the Iselten Alp, in the valley of the Lutschine, between 
 
 j. gypsum. m. marl. 
 
 Fig. 80. 
 
CH. V.] 
 
 CURVED STRATA IN THE ALPS. 
 Fig. 8L 
 
 L\\\\\\\\\\\\ 
 
 59 
 
 Unterseen and Grindelwald, curves of calcareous shale are seen from 
 1000 to 1500 feet in height, in which the beds sometimes plunge down 
 vertically 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 Pyre- 
 nees, as those near Gavarnie, at the base of Mount Perdu. 
 
 Unconformable stratification. Strata are said to be unconformable, 
 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 case it is evi- 
 
 Fig. 83. 
 
 Unconformable junction of old red sandstone and Silurian schist at the Siccar Point, near St Abb's 
 Head, Berwickshire. See also Frontispiece. 
 
 dent that a period had elapsed between the production of the two sets 
 of strata, and that, during this interval, the older series had been tilted 
 
60 UNCONFOKMABLE STRATIFICATION. [On. V 
 
 and disturbed. Afterwards the upper series was thrown down in hori- 
 zontal 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, c?, <#, 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 breaking 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 dis- 
 sected 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 pre- 
 sented 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 immeasurable 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 listanod with earnestness and admiration to the 
 philosopher who was now unfolding to us the order and series of these 
 wonderful events, we became sensible how much farther reason may 
 sometimes go than imagination 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 colored 
 from nature by the youngest son of the late Sir James Hall. It was im- 
 possible, however, to do justice to the original sketch, in an engraving, as 
 the contrast of the red sandstone and the light fawn-colored vertical schists 
 
 * Biographical account of Dr. Hutton. 
 
 f Playfair, ibid. ; see his Works, Edin. 1822, vol. iv. p. 81. 
 
CH, V.] 
 
 FISSURES IN STRATA. 
 
 61 
 
 could not be expressed. From the point of view here selected, the under- 
 lying 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 unconformable strata, the inferior rock has not only been denuded, but 
 drilled by perforating shells. Thus, for example, at Autreppe and Gusigny, 
 near MODS, beds of an ancient (primary or paleozoic) limestone, highly 
 
 Fig. 84 
 
 Junction of unconformable strata near Mons, in Belgium. 
 
 inclined, and often bent, are covered with horizontal strata of greenish 
 and whitish marls of the Cretaceous formation. The lowest and there- 
 fore the oldest bed of the horizontal series is usually the sand and con- 
 glomerate, a, in which are rounded fragments of stone, from an inch to 
 two feet in diameter. These fragments have often adhering shells at- 
 tached to them, and have been bored by perforating mollusca. The 
 solid surface of the inferior limestone has also been bored, so as to ex- 
 hibit cylindrical and pear-shaped cavities, as at c, the work of saxicavous 
 mollusca ; and many rents, as at 6, 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 separated 
 parts remaining in the same places ; but we often find a fissure, several 
 inches or yards wide, intervening between the disunited portions. These 
 fissures are usually filled with fine earth and sand, or with angular frag- 
 ments of stone, evidently derived from the fracture of the contiguous 
 rocks. 
 
 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 derangement 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 
 
62 
 
 FAULTS. 
 Fig. 85. 
 
 [Oa V 
 
 TJ D 
 
 Faults. A B perpendicular, C D oblique to the horizon. 
 
 the strata on each side of the faults A B, CD, continue parallel to one 
 another ; in other cases, the strata on each side are inclined, as in a, 6, c, d 
 
 Fig. 86. 
 
 p d c f, a 
 
 E F, fault or fissure filled with rubbish, on each side of which the shifted 
 strata are not parallel. 
 
 (fig. 86), though 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 perpendicu- 
 lar, 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 ;he union of two or more faults. In other words, the 
 disjointed strata have in certain districts been subjected to renewed move- 
 ments, 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 earth- 
 quakes ; for land has been moved, and its level, relatively to the sea, 
 considerably altered, within the period when much of the alluvial sand 
 and gravel now covering the surface of continents was deposited. 
 
 * Playfair, Illust. of Hutt. Theory, 42. 
 f 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. 8Y) represent the surface of a 
 country on which the strata a b c frequently crop out, an observer, who 
 
 Fig. 87. 
 
 Apparent alternations of strata caused by vertical faults. 
 
 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 origi- 
 nal 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 success- 
 ively, 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 de- 
 nudation 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 dis- 
 covered 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 sud- 
 denly in his workings, upon reaching the- strata of sandstone c, or on ar- 
 riving at the line of fault F, he comes partly upon the shale &, and partly 
 on the sandstone c, and on reaching E he is again stopped by a wall com- 
 posed 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 fissure are scored by grooves, such 
 
 * Conybeare and Phillips, Outlines, (fee. p. 376. 
 
64: ORIGIN OF GREAT FAULTS. [On. V. 
 
 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 extended 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 "slicken- 
 sides," that the striae are not always parallel, but often curved and ir- 
 regular. 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 extensive chasm d e, formed at the depth of several miles, 
 
 Fig. 88. 
 
 whether by 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. JSTow, if this region be convulsed by earthquakes, the 
 fissures /#, 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 subterranean 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 f g, and the edges 
 of the falling mass being continually more broken and triturated at each 
 convulsion. If, as is not improbable, 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 previous 
 friction. In the present state of our ignorance of the causes of subsidence, 
 an hypothesis which can explain the great amount of displacement in 
 
 * Phillips, Geology, Lardner's Cyclop, p. 41. 
 
Cn. V.] ORIGIN OF GREAT FAULTS. 65 
 
 some faults, on sound mechanical principles, by a succession of move- 
 ments, is far preferable to any theory which assumes each fault to have 
 been accomplished by a single upcast or downthrow of several thousand 
 feet. For we know that there are operations now in 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 insensibly, 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 de- 
 pressed, 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 Carboniferous, Devonian, 
 and Silurian rock was formed, whilst the bed of the sea was all the time 
 continuously and tranquilly subsiding.* Whatever may have been the 
 changes which the solid foundation underwent, whether accompanied by 
 the melting, consolidation, crystallization, or desiccation of subjacent min- 
 eral 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 importance 
 in the aggregate, that we are able to explain the phenomena of denuda- 
 tion, 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 equi- 
 librium, 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 ;" Memoir?, yols. 
 L and ii. by Sir H. de la Beche, Mr. A, C. Ramsay, and Mr. John Phillips. 
 
 5 
 
66 DENUDATION OF ROCKS. [On. VL 
 
 CHAPTER VI. 
 
 DENUDATION. 
 
 Denudation defined Its amount equal to the entire mass of stratified deposits in 
 the earth's crust Horizontal sandstone denuded in Ross-shire Levelled sur- 
 face 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, winch has been occasionally spoken of in the preceding 
 chapters, is the removal of solid matter by water in motion, whether of 
 rivers or of the waves and currents of the sea, and the consequent laying 
 bare of some inferior rock. 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 accompaniment of 
 the production of all new strata of mechanical origin. The formation 
 of every new deposit by the transport of sediment and pebbles necessa- 
 rily 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 vol- 
 canic 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 excavation 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 re- 
 jected 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. 
 
Cn. VI] 
 
 DENUDATION OF STRATIFIED ROCKS, 
 
 67 
 
 Fig. 89. 
 
 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 re- 
 moval of transported materials in past ages! Accordingly, there are 
 different classes of phenomena, which attest in a most striking manner 
 the vast spaces left vacant by the erosive power of water. I may 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, 8, 4, in the accom- 
 panying diagram (fig. 89) ; No. 1 conglom- 
 erate, No. 2 clay, No. 3 grit, and No. 4 
 limestone, each repeated in a series of hills 
 separated by valleys varying in depth. 
 When we examine the subordinate parts of 
 these four formations, we find, in like man- 
 ner, distinct beds in each, corresponding, on the opposite sides of the 
 valleys, both in composition and order of position. No one can doubt 
 that the strata were originally continuous, and that some cause has 
 swept away the portions which once connected the whole series. A 
 torrent on the side of a mountain produces similar interruptions ; and 
 when we make artificial cuts in lowering roads, we expose, in like man- 
 ner, corresponding beds on either side. But in nature, these appearances 
 occur in mountains several thousand feet high, and separated by inter- 
 vals of many miles or leagues in extent, of which a grand exemplifica- 
 tion is described by Dr. MacCulloch, on the northwestern coast of Ross- 
 shire, in Scotland.* 
 
 Fig. 90. 
 
 Coul beg. 
 
 Valleys of denudation. 
 a. alluvium. 
 
 Suil Yeini 
 
 Coul more. 
 
 Denudation of red sandstone on northwest 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 dis- 
 tinctly 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 sum- 
 mits 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 sand- 
 stone, and that masses from 1000 to more than 3000 feet in thickness have 
 been removed. 
 
 * Western Islands, vol. ii. p. 93, pi. 31, fig. 4. 
 
68 DENUDATION. [Cir. VI 
 
 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 adjacent 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 obser- 
 vations 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 al- 
 ways have been borrowed from another ; a truth which, obvious as it 
 may seem when thus stated, must be repeatedly impressed on the stu- 
 dent'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 sedi- 
 mentary matter, as if the new strata were not always produced at the 
 expense of pre-existing rocks, stratified or unstratified. By duly reflect- 
 ing 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 acces- 
 sions 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 correct indication of the 
 rate at which the denuding operation was carried on. 
 
 Perhaps the most convincing evidence of denudation on a magnificent 
 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, although 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 ac- 
 
CIL VL] 
 
 OF STRATIFIED ROCKS. 
 
 69 
 
 curacy. 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 
 
 Fig. 91. * 
 
 Faults and denuded coal strata, Ashby de la Zouch. (Mammat.) 
 
 rise to the height of 500 feet above the corresponding beds on the other 
 side. But the uplifted strata do not stand up 500 feet above the general 
 surface ; on the contrary, the outline of the country, as expressed by the 
 line 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 precipitous 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 subter- 
 ranean movements.f 
 
 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 districts above re- 
 ferred to, they consist of rounded and angular fragments of hard sand- 
 stone, 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 discordant 
 .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 magni- 
 tude, which have thrown the rocks up or down several hundred feet. 
 Yet the superficial inequalities to which these dislocated masses origi- 
 nally 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 fractured 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 
 
 * See Mammal's Geological Facts, &c., p. 90, and plate, 
 f Conybeare's Report to Brit. Assoc. 1842, p. 381. 
 
TO ORIGIN OF VALLEYS. [Cut. VI 
 
 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 their 
 different degrees of hardness ; the hard trap of the Wreldn, 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 val- 
 leys." 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 magni- 
 tude 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 ex- 
 plain the observed phenomena by the aid of so gratuitous an hypothesis. 
 
 On the other hand, a machinery of a totally different kind seems capa- 
 ble of giving rise to effects of the required magnitude. It has now been 
 ascertained that the rising and sinking of extensive portions 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 sometimes 
 run for a thousand miles or more in one direction, retaining a considera- 
 ble velocity even at the depth of several hundred feet. Under these cir- 
 cumstances, 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 volu- 
 minous deposit may be entirely swept away, so that, in the absence of 
 faults, no evidence may remain of the denuding operation. It may in- 
 deed be affirmed that the signs of waste will usually be least obvious 
 where the destruction has been most complete ; for the annihilation 
 
 * Prestwich, Geol. Trans, second series, vol. v. pp. 452, 473v 
 
CH. VI] INLAND SEA-CLIFFS. 71 
 
 may have proceeded so far, that no ruins are left of the dilapidated 
 rocks. 
 
 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, espe- 
 cially 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 mountain 
 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 excava- 
 tion, 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 move- 
 ments and denudation. 
 
 I may now recapitulate a few of the conclusions to which we have ar- 
 rived : 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 originally 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 denu- 
 dation, 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 southeast of England, when treating in Chapter XLX. of the denu- 
 dation 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 othei 
 counties in England. These ancient beach-lines often form terraces ol 
 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 ef- 
 
72 INLAND SEA-CLIFFS. [On. VI 
 
 faced, wherever, in consequence of the altered state of the tides and cur- 
 rents, the sea has 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 ex- 
 ample 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 northeast and southwest, or parallel 
 to the contiguous coast. This sudden fall of about 50 feet conducts us 
 fiom the higher platform of the Landes to a lower plain which extends 
 
 Fig. 92. 
 
 Section of inland cliff at Abesse, near Dax. 
 a. Sand of the Landes. &. Limestone. c. Clay. 
 
 to the sea. The outline of 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 6, con- 
 taining 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 cal- 
 careous 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, favored the waste by allowing the more solid super- 
 incumbent stone 6 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, d e, 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, earthquakes must 
 not be forgotten. During violent shocks, steep and overhanging cliffs 
 are often thrown down and become a heap of ruins. Sometimes une- 
 qual movements of upheaval or depression entirely destroy that horizon- 
 
Cn. n.] INLAND SEA-CLIFFS AND TERRACES. 78 
 
 tality 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 distances 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 re- 
 semble those now washed by the waves of the Mediterranean, where 
 they are formed of calcareous rock, especially if the rock be a hard crys- 
 talline 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 pro- 
 duces. 3. A line of littoral caverns at the foot of the cliffs. 4. A con- 
 solidated 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 calcareous cement. Similar aggrega- 
 tions 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 lithodomi 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 
 living 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 Xavarino 
 on cliffs in the interior 125 feet high above the Mediterranean. 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 corals. Such effects are traced not 
 
74 INLAND SEA-CLIFFS [On. VI 
 
 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 frorn 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 platform 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 intermittance 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-ehore, would 
 have presented a nearly similar aspect. But if pauses occur in the pro- 
 cess 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 sedimentary 
 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 (6, 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 perfo- 
 rated by lithodomi. Within the grotto, also, at the same level, similar 
 perforations occur ; and so numerous are the holes, that the rock is com- 
 pared by Hoffmann to a target pierced by musket balls. But in ordei 
 
On. VI] 
 
 IN THE ISLAND OF SICILY. 
 
 75 
 
 to expose to view these marks of boring-shells in the interior of the cave, 
 it was necessary first to remove a mass of breccia, which consisted of 
 
 Fig. 93. 
 
 
 a. Monte Grifone. 6. Cave of San Ciro.* 
 
 c. Plain of Palermo, in \vhich are Newer Pliocene strata of 
 limestone and sand. d. Bay of Palermo. 
 
 numerous fragments of rock, and an immense quantity of bones of the 
 mammoth, hippopotamus, and other quadrupeds, imbedded in a dark 
 brown calcareous 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 deposit 
 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 be- 
 fore mentioned (p. 74). 
 
 There are also numerous instances in Sicily of terraces of denudation. 
 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 may 
 be traced forming a continuous and lofty precipice, a 5, fig. 94, facing 
 towards the sea, and constituting the abrupt termination of a calcareous 
 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 6, 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 precipice a 6, at which time the sur- 
 
 * Section given by Dr. Christie, Edin. New PhiL Journ. No. xxm. called by 
 mistake the Cave of Mardolce, by the late M. Hoffmann. See account by Mr. S. . 
 P. Pratt, F. G. S. Proceedings of Geol. Soc. No. 32, 1S3S. 
 
76 
 
 INLAND SEA- CLIFFS AND 
 
 [On. VI. 
 
 face of the terrace c b must have' been covered by the Mediterranean. 
 There was a pause, therefore, in the upward movement, when the waves 
 
 Fig. 94. 
 
 Sea 
 
 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, A, once existed, and that 
 the sea, during a long interval free from subterranean movements, 
 advances along the line c 6, all preceding cliffs must have been 
 swept away one after the other, and reduced to the single precipice 
 ab. 
 
 That such a series of smaller cliffs, as those represented at e, /, g, A, 
 fig. 94, did really once exist at intermediate heights in place of the single 
 precipice a 6, 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 limestone is shaped out 
 into a great succession of ledges, separated from each other by small 
 vertical cliffs. These are sometimes so numerous, one above the other, 
 
 Fig. 95. 
 
 Valley called Gozzo degli Martiri, below Melilli, Val di Note. 
 
 that where there is a bend at the head of a valley, they produce an ef- 
 fect singularly resembling the seats of a Roman amphitheatre. A good 
 
CH. VI.] TEREACES IX SICILY. 77 
 
 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, precipitous 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 bot- 
 tom, on the opposite sides of a gorge, may be accounted for, as already 
 hinted, bv supposing the sea to have stood successively at many different 
 levels, as at a a, b 5, c c, in the accompanying fig. 96. But the causes 
 of the gradual contraction of the valley from above downwards may 
 
 Fig. 96. 
 
 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 propor 
 tion 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 ex- 
 pected, to whichever of the two hypotheses above explained we incline ; 
 for, according 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 
 encroach so far on the other as to unite several smaller cliffs into 
 one. 
 
 Before quitting the subject of ancient sea-cliffs, carved out of lime- 
 stone, I shall mention the range of precipitous rocks, composed of a 
 white marble of the Oolitic period, which I have 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 
 
78 
 
 KOCKS WORN BY THE SEA. 
 
 [On. VI 
 
 round them, facing towards all points of the compass, as if they had 
 once formed rocky islets near the shore.* 
 
 Captain Bayfield, in his survey of the Gulf of St. Lawrence, discov- 
 ered in several places, especially in the Mingan islands, a counterpart 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 prin- 
 cipal grooves scooped out of the limestone pillars. These beaches con- 
 sisted 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 favored with other views of rocks on the 
 same coast, drawn by Lieut. A. Bo wen, R. N. (See fig. 97.^1 
 
 Fig. 97. 
 
 Limestone columns in Niaplsca Island, in the Gulf of St. Lawrence. Height 
 of the second column on the left, 60 feet. 
 
 In the North- American beaches above mentioned rounded fragments 
 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 atmos- 
 pheric decomposition on the surface, or the cavities alluded to would 
 have disappeared. 
 
 Fig. 98. 
 
 The North Eocks, Bermuda, lying outside the great coral reef. 
 A. 16 feet high, and B. 12 feet. c. c. Hollows worn by the sea. 
 
 * I was directed by M. Deshayes to this spot, which I visited in June, 1833. 
 f See Trans, of Geol. Soc. second series, vol. v. plate v. 
 
CH. VII.] ' ALLUVIUM. 79 
 
 We have an opportunity of seeing in the Bermuda islands the 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 by Capt. Nelson, R. E., the 
 excavations c, c, c, have been scooped out by the waves in a stone of very 
 modern date, which, although extremely hard, is full of recent corals and 
 shells, some of which retain their color. 
 
 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 carefully 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 comparativb.y 
 modem ; 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 con 
 trary, they are, upon the whole, extremely 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 movements, as the adjoining calcareous rocks. 
 
 CHAPTER VE. 
 
 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 subjacent 
 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 fragments of rock, some an- 
 gular 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 prob- 
 
80 
 
 ALLUVIUM IN AUVERGNE. 
 
 [Ca VII. 
 
 able connection with the 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 chaptei 
 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 diy 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 unreason- 
 able 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 al- 
 ready acquired in some degree its present configuration before any volca- 
 noes were in activity, and before any igneous matter was superimposed 
 upon the granitic and fossiliferous formations. The pebbles therefore in 
 the older gravels are exclusively constituted of granite and other aborigi- 
 nal rocks ; and afterwards, when volcanic vents burst forth into eruption, 
 
 Fig. 99. 
 
 Lavas of Auvergne resting on alluviums of different ages. 
 
 those earlier alluviums were covered by 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 
 
CH. VII] 
 
 ALLUVIUM. 
 
 81 
 
 of these plains differed from the first or upland alluvium, by containing 
 in it rounded fragments of various volcanic rocks, and often bones be- 
 longing 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, TOO 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 nar- 
 row 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 under- 
 mining their banks and grinding down into pebbles or sand, columns 
 of basalt and fragments 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 disintegra- 
 tion 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, con- 
 forming to all the inequalities of the fundamental rocks (fig. 100). Oc- 
 casionally, a small mass, as at c, appears 
 detached, and as if included in the subja- 
 cent formation. Such isolated portions are 
 usually sections of winding subterranean 
 hollows filled up with alluvium. 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 which the roots of large 
 trees have once occupied, gravel and sand 
 ha-ving been introduced after their decay. 
 
 Fig. 100. 
 
 a. Vegetable soil ft. Alluvium. 
 
 c. Mass of same, apparently detached. 
 
82 SAND-PIPES. [CH. VII 
 
 But there are other deep hollows of a cylindrical form found in Eng- 
 land, France, and elsewhere, penetrating the white chalk, and filled with 
 sand and gravel, which are not so readily explained. They are some- 
 times called "sand-pipes," or "sand-galls," and "puits naturels," in 
 France. Those represented in the annexed cut were observed by me in 
 
 Fig. 101. 
 
 Band-pipes in the chalk at Eaton, near Norwich. 
 
 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 ofthem 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 ob- 
 served 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 c?, 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 
 
 * Trimmer, Proceedings of Geol. Soc. vol. iv. p. 7, 1842. 
 
CH. VII.] ALLUVIUM. 83 
 
 at b b, similar unrounded nodules of flint, still preserving their irregular 
 form and white coating, are found at various depths in the midst of the 
 loose materials filling the pipe. These have evidently been detached 
 from regular layers of flints occurring 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, >,*nd 
 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, Maestricht. These 
 hollows are filled with pebbles and clay, derived from overlying beds of 
 gravel, and all terminate downwards like those of Norfolk. I was in- 
 formed that, 6 miles from Maestricht, one of these pipes, 2 feet in diam- 
 eter, 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 distinc- 
 tion 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 neighboring 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 materials, 
 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 en- 
 
 * See Lyell on Sand-pipes, Ac. Phil. Mag. third series, voL xv. p. 257, Oct. 1839. 
 
84: ALLUVIUM. [On. VII 
 
 tombed in the strata, which enable us to determine their age and 
 mode of origin, we regard them as part of the regular series of fos- 
 siliferous formations, whereas, if there are no fossils, we have frequently 
 no power of separating them from the general mass of superficial al- 
 luvium. 
 
 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 decomposition 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 for- 
 merly. But suah 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 hydrographical 
 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 cany 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, 
 therefore, 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 would begin to aug- 
 ment. Each of them would be less given to overflow its alluvial plain ; 
 and their power of carrying earthy matter seaward, and of scouring out 
 and deepening their channels, will be sustained till, after a lapse of many 
 thousand years, each of them has eroded a new 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 fringing the valley sides in the form of a terrace apparently flat, 
 but in reality sloping down with the general inclination of the river. 
 Everywhere this terrace will present cliff's 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 
 
 * Principles of Geology, 7th ed. p. 506, 8th ed. p. 509. 
 
CH. VIL] 
 
 RIVER TERRACES. 
 
 85 
 
 oscillations of level, I have endeavored to show in my description of that 
 country;* and the freshwater shells of existing species and bones of 
 land quadrupeds, partly of extinct races preserved in the terraces of flu- 
 viatile origin, attest the exclusion of the sea during the whole process 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 ex- 
 ample, 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 up- 
 heaved area would in its turn be a sea-shore, and inight 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. Mate- 
 rials 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 corresponding in height. 
 
 Fig. 102. 
 
 Eiver Terraces and Parallel Eoads. 
 
 These terraces are seldom continuous for great distances, and their 
 surface slopes downwards, with an inclination similar ta that of the river. 
 They are readily explained if we adopt the hypothesis before 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 
 
 * Second Visit to the U. S, vol. ii. chap. 34. 
 
86 PAEALLEL KOADS [On. VII 
 
 operation being afterwards repeated at lower levels,, there will be several 
 successive cliffs and terraces. 
 
 Parallel roads. The parallel shelves, or roads, as they have been 
 called, of Lochaber or Glen Roy and other contiguous valleys in Scot- 
 land, 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, twc, 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 horizontally, 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 artificially 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 depo- 
 sition of detritus, precisely similar to that which is dispersed 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 throughout 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 pro- 
 portion 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 descrip- 
 tion of all the geographical circumstances attending these singular ter- 
 races, or to discuss the ingenious theories which have been severally 
 proposed to account for them by Dr. MacCuiloch, Sir T. D. Lauder, and 
 Messrs. Darwin, Agassiz, Milne, and Chambers. There is one point, 
 however, 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 moun- 
 
CH. VII] OF GLEX ROY. 87 
 
 tains subject to disintegration by frost or the action of torrents, some 
 loose matter is washed down annually, especially 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 
 
 ~B in which Dr. MacCulloch and Mr. Darwin 
 
 A R C Supposed original surface of SU pp Ose t he roads" to constitute mere in- 
 CD. Roads or shelves in the outer dentations in a superficial alluvial coating 
 
 alluvial covering of the hill. \ , . 
 
 which rests upon the hill-side, and consists 
 chiefly of clay and sharp unrounded stones. 
 
 Among other proofs that the parallel roads have really been formed 
 along the margin of a sheet of water, it may be mentioned, that wher- 
 ever an isolated hill rises in the middle of the glen above the level of 
 any particular shelf, a corresponding shelf is seen at the tame 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 unin- 
 terrupted 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 com- 
 position, and the slope and inclination of the ground very similar, started 
 the conjecture that these valleys were once blocked up by enormous gla- 
 ciers descending from Ben JS"evis, giving rise to what are called in Swit- 
 zerland 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 after- 
 wards 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 Switzerland. Al- 
 lusion 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 previous lacustrine theory, by 
 
88 PARALLEL ROADS OF GLEN ROY. [Cn. VH 
 
 accounting more easily for the temporary existence and entire disappear* 
 ance of lofty transverse barriers, although the height required for the im- 
 aginary 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 station- 
 ary for so many centuries as to allow of the accumulation of an extraor- 
 dinary quantity of detrital matter, and the excavation, at many points im- 
 mediately 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 horizontality 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 al- 
 luded 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- 
 mentioned 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 nar- 
 rowness. In a chart of the Falkland Islands by Capt. Sullivan, R. N., it 
 appears that there are several examples there of straits where the sound- 
 ings 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 relative 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 tho 
 islands, if the sea were to subside."* 
 
 The first of the difficulties above alluded to, namely, the non-extension 
 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 have been time for the removal of 
 
 * " Ancient Sea Margins," p. 114, by R. Chambers. 
 
CH. VI1L] CHRONOLOGY OF ROCKS. 89 
 
 the gravel. In one case an intermediate 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 horizontality 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 formation 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 horizon- 
 tality ; 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 upper- 
 most shelf, or 1250 feet, simultaneously all over the globe, while the land 
 remained unmoved, is a view which will find favor with very few geolo- 
 gists, for the reasons explained in the fifth chapter. 
 
 The student will perceive, from the above sketch of the controversy re- 
 specting 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. 
 
 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 tran- 
 sition class Xeptunian theory Hutton 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 intended 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. 
 
9Q CLASSIFICATION OF KOCKS. [On. VIII 
 
 IN the first chapter it was stated that the four great classes of locks, the 
 aqueous, the volcanic, the plutonic, and the metamorphic, would each be 
 considered not only in reference to their mineral characters, and mode of ori- 
 gin, 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 argil- 
 laceous 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 convenient 
 and natural method to begin by establishing a chronology for these strata, 
 and then to refer as far as possible to the same divisions the several groups 
 of plutonic, volcanic, and metamorphic rocks. Such a system of classifica- 
 tion is not only recommended by its greater clearness and facility of ap- 
 plication, but is also best fitted to strike the imagination by bringing into 
 one view the contemporaneous revolutions 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 comprehend. 
 
 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 mem- 
 bers of the aqueous and volcanic orders were produced ; and although 
 this idea has long been modified, and is nearly exploded, it will be neces- 
 sary 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, pro- 
 posed to divide rocks into three classes, the first and oldest to be called 
 primitive, comprising the hypogene, or plutonic and metamorphic rocks ; 
 the next to be termed secondary, comprehending the aqueous or fossilif- 
 erous 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 de- 
 rived 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 or- 
 ganic remains, must have been mechanical deposits, produced after the 
 
CH. VIII.] NEPTUNIAN THEOKY. 91 
 
 planet had become the habitation of animals and plants. This bold 
 generalization, although anticipated 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 celebrated for his improved methods of discriminating the minera- 
 logical 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 mechanical origin and or- 
 ganic remains. For this group, therefore, forming a passage between 
 Lehman's primitive and secondary rocks, the name of ubergang or transi- 
 tion was proposed. They consisted principally of clay-slate and an ar- 
 gillaceous sandstone, called grauwacke, and partly of calcareous beds. 
 It 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 of flbtz, or " a level floor ;" 
 and every deposit more modern than the chalk, which was classed as the 
 uppermost of the flotz series, was designated " the overflowed land," an 
 expression which may be regarded as equivalent to alluvium, although 
 under this appellation 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 
 oeds," and the horizontality of the flotz, or newer fossiliferous strata, were 
 mere local accidents, they soon abandoned the term flotz ; and 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 al- 
 ready 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.* 
 
 The 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 a universal chaotic ocean, holding 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 chemical, because the waves and currents 
 had already begun to wear down solid land, and to give rise to pebbles, 
 sand, and mud ; nor entirely without fossils, because a few of the first 
 marine animals had begun to exist. After this period, the secondary for- 
 * See Principles of Geology, vol. i. chap. iv. 
 
92 ON THE TERM " TRANSITION." [Cn. Vlll 
 
 mations were accumulated in waters resembling those of the present ocean, 
 except at certain intervals, when, from causes wholly unexplained, a par- 
 tial recurrence of the " chaotic fluid" took place, during which various 
 trap rocks, some highly crystalline, were formed. This arbitrary hypothe- 
 sis rejected all intervention of igneous agency, volcanoes 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 phe- 
 nomena 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 strata called primi- 
 tive had not been precipitated from a primaeval ocean, but were sediment- 
 ary 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 favor ; 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 conformity 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, inter- 
 mediate 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 transition, 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- 
 
CH. VIIL] CHANGES OF NOMENCLATURE. 93 
 
 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 tran- 
 sition, 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 refer- 
 ence 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, in- 
 duced 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 metamor- 
 phic 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, onr work o'erflowa. 
 
 But the reverse is true in geology ; for here it is our work which contin- 
 ually 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, by the force of association 
 to perpetuate error ; so that dogmas renounced by the reason still retain 
 a strong hold upon the imagination. 
 
 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 men- 
 struum 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 crys- 
 talline 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 
 proceeded, the aqueous vapor in the atmosphere was condensed, and, fall- 
 ing in rain, gave rise to the first thermal ocean. So high was the tem- 
 perature 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, al- 
 though not so intense as to prevent the introduction and increase of some 
 
94 CHRONOLOGICAL ARRANGEMENT [Ca VIII. 
 
 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 or- 
 ganic beings, were still preserved ; and the mistaken notion that all the 
 semi-crystalline and partially fossiliferous rc>cks belonged to one period, 
 while all the earthy and uncrystalline formations originated at a subse- 
 quent 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 cer- 
 tainly no geological proofs that the granite which constitutes the founda- 
 tion 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 dis- 
 tinct and often distant periods. One mass was solid, and had been frac- 
 tured, 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 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 universality 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 simultaneously. 
 
 In the present work the four great classes of rocks, the aqueous, plutonic, 
 volcanic, aiid metamorphic, will form four parallel, or nearly parallel, col- 
 umns in one chronological table. They will be considered as four sets of 
 monuments relating to four contemporaneous, or nearly contemporaneous, 
 series of events. I shall endeavor, 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 
 geological period, and how the earth's crust may have been continually 
 modelled, 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 vol- 
 canic rocks break out at the surface, and are connected with reservoirs of 
 melted matter at vast depths in the bowels of the earth, so, at every 
 era of the past, fossiliferous deposits and superficial igneous rocks were in 
 progress contemporaneously with others of subterranean and plutonic ori- 
 gin, and some sedimentary strata were exposed to heat and made to as- 
 sume a crystalline or metamorphic structure. 
 
 It can by no means be taken for granted, that during all these changes 
 the solid crust of the earth has been increasing in thickness. It has been 
 
Ca VIII] OF KOCKS IN GENERAL. 95 
 
 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 crystalline rocks, at each successive era, may merely have 
 counterbalanced the loss sustained by the melting of materials previously 
 consolidated. As to the relative antiquity of the crystalline foundations of 
 the earth's crust, when compared to the fossiliferous and volcanic rocks 
 which they support, I have already stated, in the first chapter, that to pro- 
 nounce an opinion on this matter is as difficult as at once to decide which 
 of the two, whether the foundations or superstructure of an ancient city built 
 on wooden piles, may be the oldest. We have seen that, to 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, un- 
 til 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. 
 
 After the observations which have now been made, the reader will per- 
 ceive that the term primary must either be entirely renounced, or, if re- 
 tained, 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 con- 
 fusion, 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 -jraXcuov, " 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 fxetfof, " middle," <fec. ; and Caino- 
 zoic, for tertiary, from xaivo^, " recent," <fec. ; but the terms primary, sec- 
 ondary, and tertiary are synonymous, and have the claim of priority in 
 their favor. 
 
 If we can prove any plutonic, volcanic, or metamorphic rocks to be 
 older than the secondary formations, such rocks will also be primary, ac- 
 cording to this system. Mr. Boue, having with propriety excluded the 
 metamorphic rocks, as a class, from the primary formations, 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 contemporaneous 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 volcanic, plutonic, 
 or metamorphic rocks, which have originated since the deposition of the 
 chalk, these also will rank as tertiary formations. 
 
96 TESTS OF THE DIFFERENT AGES [Ca. IX. 
 
 It may perhaps be suggested that some metamorpliic strata, and some 
 granites, may be anterior in date to the oldest of the primary fossilifer- 
 ous rocks. This opinion is doubtless true, and will be discussed in future 
 chapters ; but I may here observe, that when we arrange the four classes 
 of rocks in four parallel columns in one table of chronology, it is by no 
 means assumed that these columns are all of equal length ; one may 
 begin at an earlier period than the rest, and another may come down to 
 a later point of time. 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, secondary, and tertiary rocks of the aqueous or fos- 
 siliferous class, and in like manner primary, secondary, and tertiary hypo- 
 gene formations, we may not be yet acquainted with the most ancient of 
 the primary fossihferous beds, or with the newest of the hypogene. 
 
 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 
 formation Proofs that distinct species of animals and plants have lived at suc- 
 cessive periods Distinct provinces of indigenous species Great extent of 
 single provinces 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 Prin- 
 cipal 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 fossilif- 
 erous 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 character ; 
 and, thirdly, organic remains. Some aid can occasionally be derived 
 from a fourth kind of proof, namely, the fact of one deposit including in 
 it fragments of a pre-existing rock, by which the relative ages of the two 
 may, even in the absence of all other evidence, be determined. 
 
 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 vol- 
 umes of history, in which each writer has recorded the annals of his own 
 
CH. IX.] OF AQUEOUS ROCKS. 97 
 
 times, and then laid down the book, with the last written page upper- 
 most, upon the volume in which the events of the era immediately pre- 
 ceding 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 regions 
 where, as the student has already been informed, the beds have been dis- 
 turbed, 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 superpo- 
 sition must be doubtful, and he then endeavors to find sections in some 
 neighboring district where the strata are horizontal, or only slightly in- 
 clined. Here the true order of sequence of the entire series of deposits 
 being ascertained, a key is furnished for settling the chronology of those 
 strata where the displacement is extreme. 
 
 Mineral character. The same rocks may often be observed to retain for 
 miles, or even hundreds of miles, the same mineral peculiarities, if we fol- 
 low 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 direc- 
 tion transverse to the planes of stratification, this uniformity ceases almost 
 immediately. In that case we can scarcely ever penetrate a stratified mass 
 for a few hundred yards without beholding a succession of extremely dis- 
 similar rocks, some of fine, others of coarse grain, some of mechanical, others 
 of chemical origin ; some calcareous, others argillaceous, and others silice- 
 ous. 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 differ- 
 ent kinds of matter. The first observers were so astonished at the vast 
 spaces over which they were able to follow the same homogeneous 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 forma- 
 tions, 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 sedi- 
 ment 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 arena- 
 ceous, and finally passes into sand, or sandstone. We may then follow this 
 sandstone, already proved by its continuity to be of the same age, through- 
 out another district a hundred miles or more ia length. 
 
 Organic remains. This character must be used as a criterion of the 
 
98 TESTS OF THE DIFFERENT AGES [On. IX 
 
 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 min- 
 eral 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 indefi- 
 nite 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 con- 
 viction, that at successive periods of the past, the same area of land and 
 water has been inhabited by species of animals and plants even more 
 distinct than those which now people the antipodes, or which now co- 
 exist in the arctic, temperate, and tropical zones. It appears, that from 
 the remotest periods there has been ever a coming in of new organic 
 forms, and an 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 reappeared 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, 
 
 datura 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 sedimentary series ; exhib- 
 iting in each position so perfect an identity of mineral aspect as to be 
 undistinguishable. Such exact repetitions, however, of the same mix- 
 tures of sediment have not often been produced, at distant periods, in 
 precisely the same parts of the globe ; and even where this has hap- 
 pened, we are seldom in any danger of confounding together the monu- 
 ments 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 stratification 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 
 endeavored to point out the extent and probable origin of these separate 
 divisions ; and it was shown that climate is only one of many causes on 
 
CH. IX.] OF AQUEOUS ROCKS. 99 
 
 which they depend, and that difference of longitude as well as latitude is 
 generally accompanied 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 adjoining 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 favorable 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, es- 
 pecially those of marine animals, is very great; and our geological 
 researches have proved that the same laws prevailed at remote periods ; 
 for the fossils are often identical throughout wide spaces, and in de- 
 tached 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 com- 
 mon 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 contem- 
 poraneous 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 occa- 
 sionally 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 characters, 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 sepa- 
 
100 TESTS OF THE DIFFERENT AGES [Cn. IX, 
 
 rated 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 exam- 
 ple, the testacea, zoophytes, and fish of the Red Sea are, as a group, ex- 
 tremely distinct from those inhabiting the adjoining parts of the Mediter- 
 ranean, 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 pe- 
 riod the bed of the Red Sea should be laid dry, the geologist might ex- 
 perience great difficulties in endeavoring 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 northwestern 
 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, not- 
 withstanding 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 ter- 
 restrial spoils into two or more seas inhabited by different marine species, 
 it will much more frequently happen, that the coexistence 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 Eu- 
 rope, north of Africa, and northwest 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 demarca- 
 tion 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 ob- 
 serving carefully the fossils of all the intermediate places. His success 
 in thus acquiring a knowledge of the zoological or botanical geography 
 
CH. IX.] 
 
 OF AQUEOUS KOCKS. 
 
 101 
 
 of very distant eras has been mainly owing to*tld?;'Cirdum3tance r *th*t * 
 the mineral character has no tendency to be affected' by climate. " A 
 large river may convey yellow or red mud into some part of ttel oc4tn, : 
 where it may be dispersed by a current ovej ah area 'severa? 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 temperate 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 homo- 
 geneous composition ; and if so, palaeontological characters will be of 
 more importance in geological classification than the test of mineral com- 
 position ; but it is idle to discuss the relative ^alue of these tests, as the 
 aid of both is indispensable, and it fortunately happens, that where the 
 one criterion fails, we can often avail ourselves of the other. 
 
 Test by included fragments of older rocks. It was stated, that inde- 
 pendent 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 may 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 forarniniferae, 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 fossil- 
 iferous 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 arrangement, we immediately find 
 that a few only of the entire series of groups occur one upon the other 
 in any single section or district. 
 
 The thinning out of individual strata was before described (p. 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 super- 
 imposed formations are present ; but in consequence of some of them 
 
102 
 
 CHRONOLOGICAL ARRANGEMENT 
 
 [CH. IX. 
 
 , t v _ ., . _ c ... No. 5 are absent at one extremity of the sec- 
 
 tic-X andNt>. 4 a't ihfe* other. 
 
 i *Iojl2ir' *^tifi^xed diagram, fig. 105, a real section of the geological 
 formtitioife" in ^ 1 - neighborhood of Bristol and the Mendip Hills, is pre- 
 sented to the reader as laid down on a true scale by Professor Ramsay, 
 where the newer groups 1, 2, 3, 4 rest unconforaiably on the formations 
 
 Fig. 105. 
 Duudry Hill. 
 
 Section South of Bristol. A. C. Eamsay, 
 
 Length of section 4 miles. a, 5. 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. 
 
 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 superim- 
 posed 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 ab- 
 ruptly, and have left outlying patches to attest the fact of their having 
 originally covered a much wider area. 
 
 In many instances, however, the entire absence of one or more forma- 
 tions 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 in- 
 ferior 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 fossilifer- 
 ous groups, a geologist must begin with a single section, in which sev- 
 eral sets of strata lie one upon the other. He must then trace these 
 formations, by attention to their mineral character and fossils, continu- 
 ously, as far as possible, from the starting point. As often as he meets 
 with new groups, he must ascertain by superposition their age relatively 
 to those first examined, and thus learn how to intercalate them in a tab- 
 ular arrangement of the whole. 
 
 By this means the German, French, and English geologists have de- 
 termined 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. 
 
CH. IX.] 
 
 OF AQUEOUS ROCKS. 
 
 103 
 
 Groups of Fossiliferous Strata observed in Western Europe, arranged 
 in what is termed a descending Series, or beginning with the newest. 
 (See a more detailed Tabular view, pp. 104-108.) 
 
 1. Post-Pliocene, including those of the 
 
 Recent, or human period. 
 
 2. Newer Pliocene, or Pleistocene. 1 
 
 3. Older Pliocene. I Tertiary, Supracretaceous,* or 
 
 4. Miocene. j Cainozoic.f 
 
 5. Eocene. J 
 
 6. Chalk. 
 
 7. Greensand and "Wealden. 
 
 8. Upper Oolite, including the Purbeck. 
 
 9. Middle Oolite. 
 
 10. Lower Oolite. 
 
 11. Lias. 
 
 12. Trias. 
 
 13. Permian. 
 
 14. Coal. 
 
 15. Old Red sandstone, or Devonian. 
 
 16. Upper Silurian. 
 
 1 7. Lower Silurian. 
 
 ] S. Cambrian and older fossiliferous strata. 
 
 Secondary, or Mesozoic. 
 
 Primary fossiliferous, or palei* 
 zoic. 
 
 It is not pretended that the three principal sections in the above table, 
 called primary, secondary, and tertiary, are of equivalent importance, or 
 that the eighteen subordinate groups comprise monuments relating to 
 equal portions of past time, or of the earth's history. 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 flour- 
 ished, and during which different kinds of sediment were deposited in the 
 space now occupied by Europe. 
 
 If we were disposed, on palaeontological 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 pri- 
 mary, secondary, and tertiary, we might, perhaps, adopt the six groups or 
 periods given 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 founding of 
 large natural groups. 
 
 * For tertiary, Sir H. De la Beche has used the term " supracretaceous," 
 a name implying that the strata so called are superior in position to the 
 chalk. 
 
 f For an explanation of Cainozoic, see p. 95. 
 
 J Palaeontology is the science which treats of fossil remains, both animal and 
 vegetable. Etym. va\atog, palaios, ancient, ovra, onto, beings, and Aoyoj, logos, a 
 discourse. 
 
104 
 
 TABULAR VIEW OF FOSSILIFEROUS STRATA. [CH. 
 
 Fossiliferous Strata of Western Europe divided into Six Groups. 
 
 1. Post-Pliocene and 
 
 Tertiary 
 
 2. Cretaceous 
 
 3. Oolitic - 
 
 4. Triassic - 
 
 5. Permian, Carbonifer- 
 
 ous, and Devonian 
 
 6. Silurian and Cam- 
 
 brian - 
 
 V from the Post-Pliocene to the Eocene inclusive. 
 
 - from the Maestricht Chalk to the Wealden inclusive. 
 
 - from the Purbeck to the Lias inclusive. 
 
 _ j including the Keuper, Muschelkalk, and Bunter Sand- 
 stein of the Germans. 
 
 including Magnesian Limestone (Zechstein), Coal, Moun- 
 tain Limestone, and Old Red Sandstone. 
 
 from the Upper Silurian to the oldest fossiliferous rocks 
 inclusive. 
 
 But the following more detailed list of fossiliferous strata, divided into 
 thirty -five sections, will be required by the reader when he is studying 
 our descriptions of the sedimentary formations given in the next 18 
 chapters. 
 
 TABULAE YIEW 
 
 OF THE 
 
 FOSSILIFEROUS STRATA, 
 
 Showing the Order of Superposition or Chronological Succession of 
 the principal Groups. 
 
 Periods and Groups. 
 
 I. POST-TERTIARY. 
 A. POST-PLIOCENE. 
 
 RECENT. 
 
 POST-PLIOCENE, 
 
 British Examples. Foreign Equivalents and Synonyms. 
 
 I. TERRAINS CONTEMPORAINES, 
 
 ET QUATERNAIRES. 
 
 Peat of Great Britain and Ireland, 
 with human remains. (Princi- 
 ples of Geology, ch. 45.) 
 
 Alluvial plains of the Thames, 
 Mersey, and Rother, with bnried 
 ships, p. 120, and Principles, 
 ch. 48. 
 
 Ancient raised beach of Brighton. 
 b. fig. 331, p. 287. 
 
 Alluvium, gravel, brick-earth, 
 Ac. with fossil shells of living 
 species, but sometimes locally 
 extinct, and with bones of land 
 animals, partly of extinct spe- 
 cies ; no human remains. 
 
 Part of the Terrain quaternaire 
 
 of French authors. 
 Modern part of deltas of Rhine 
 
 Nile, Ganges, Mississippi, Ac. 
 Modern part of coral-reef's of Red 
 
 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. 7C2. 
 
 Part of Terrain quaternaire of 
 French authors. 
 
 Volcanic tuff of Ischia, with liv 
 ing species of marine shells 
 and without human remains or 
 works of art, p. 118. 
 
 Loess of the Rhine, with recent 
 freshwater shells, and mam- 
 moth bones, p. 121. 
 
 Newer part of boulder-formation 
 in Sweden, p. 129. Bluffs of 
 Mississippi, p. 121. 
 
 II. TERTIARY. 
 B. PLIOCENE. 
 
 NEWER 
 PLIOCENE, 
 
 or 
 Pleistocene. 
 
 Glacial drift or boulder-formation 
 of Norfolk, p. 132, of the Clyde 
 in Scotland, p. 130, of North 
 Wales, p. 136. Norwich Crag, 
 p. 154 Cave-deposits of Kirk- 
 dale, Ac., with bones of extinct 
 and living quadrupeds, p. 160. 
 
 II. TERRAINS TERTIAIRES. 
 
 Terrain quaternaire, diluvium. 
 
 Terrains tertiaires sup6rieurs, p. 
 139. 
 
 Glacial drift of Northern Europe, 
 p. 128; and of Northern United 
 States, p. 139 ; and Alpine er- 
 ratics, p. 148. 
 
 Limestone of Girgenti, p. 159. 
 
 Australian cave-breccias, p. 161. 
 
Ca IX.] TABULAR VIEW OF FOSSILIFEROUS STRATA. 105 
 
 Periods and Groups. British Examples Foreign Equivalents and Synonym*. 
 
 f Snbapennine strata, p. 173. 
 
 4. OLDER C Red Crag of Suffolk, pp. 168-170. I Hills of Rome, Monte Mario, Ac. 
 
 PLIOCENE. j Coralline cragof Suffolk, pp. 168- ^V-d^Smandy cra, p. 
 
 I Aralo-Caspian deposits, p. 175. 
 
 C. MIOCENE. 
 
 5. MIOCENE. 
 
 D. EOCENE, 
 
 6. TIPPER EOCENE 
 (Lower Miocene of 
 
 many authors). 
 
 {Marine strata of this age wanting 
 in the British Isles. 
 Leaf-bed of Mull in the Hebrides T 
 p. 179. 
 Lignite of Antrim?, p. 180. 
 
 IHempstead beds, near Yarmouth, 
 Isle of Wight, p. 192. 
 
 7. MIDDLE EOCENE, 
 
 e 
 
 8. 
 
 1. Bembridge, or Binstead Beds, 
 Isle of Wight, p. 208. 
 
 2. Osborne or St. Helen's Series, 
 p. 210. 
 
 3. Headon Series. Ibid. 
 
 4. Headon Hill Sands, and Bar- 
 ton Clay, p. 212. 
 
 5. Bagshot and Bracklesham 
 Beds, p. 213. 
 
 6. Wanting? Seep. 222. 
 
 f 1. London Clay and Bognor Beds, 
 
 1 2. P Plast'ic and Mottled Clays and 
 < Sands, and Woolwich Beds, p. 
 
 219. 
 I 3. Thanet Sands, p. 221. 
 
 III. SECONDARY. 
 E. CRETACEOUS. 
 UPPER CRETACEOUS. 
 
 r 
 
 9. MAESTRICHT j Wanting in England. 
 
 BEDS. 
 
 10. UPPER j White Chalk with Flints, of Xorth 
 
 WHITE CHALK. I and S ^ Downs, p. 240. 
 
 11. LOWER 
 
 WHITE CHALK. 
 
 13. TIPPER 
 
 GREENSAND. 
 
 Chalk without Flints, and Chalk 
 
 Marl, p. 239. 
 Chalk Marl. Ibid. 
 
 f Loose sand with bright green 
 
 I 1 grains, p. 260. 
 Firestone of Merstham, Surrey, J 
 Marly Stone with Chert, Isle of 
 Wight. I 
 
 C. TERRAINS TERTIAIEES MOT- 
 
 EJfS, PARIIE SCFEK1EURE J OR 
 FALCHS. 
 
 Falunien snpe'rieur, D'Orbigny. 
 Faluns of Touraine, p. 175. 
 Part of Bourdeaux beds, p. 178. 
 Bolderberg strata in Belgium, p. 
 
 Part of Vienna basin, p. 179. 
 
 Part of Molasse, Switzerland, p. 
 179. 
 
 Sands of James River, and Rich- 
 mond, \ irginia, United States, 
 . p. 181. 
 
 Lower part of Terrain Tertiairo 
 
 Moyen. 
 Calcaire Lacustre Snpgrieur and 
 
 Ores de Fontaineblean, p. 194. 
 Part of the Lacustrine strata of 
 
 Anvergne, p. 194. 
 Kleyu Spawen or Limbnrg beds, 
 
 Belgium Rupelian and Tong- 
 
 rian systems of Dumont, p. 188. 
 Mayence basin, p. 190. 
 Part of brown-coal of Germany, 
 
 pp. 191, 540. 
 Hermsdorf tile-clay near Berlin, 
 
 p. 189. 
 1. Gypseous Series of Montmartre, 
 
 and Calcaire lacustre superieur, 
 
 p. 223. 
 
 2 & 3. Calcaire Siliceux, p. 225. 
 2 <fc 3. Ores de Beanchamp, or 
 
 Sables Moyens, p. 226. Laecken 
 
 beds, Belgium. 
 
 4 & 5. Upper and Middle Calcaire 
 Grossier, p. 226. 
 
 5. Bruxellien, or Brussels beds of 
 
 Dumont. 
 5. Lower Calcaire Grossier, or 
 
 Glanconie Grossiere, p. 228. 
 
 5. Claibome beds, Alabama, 
 United States, p. 232. 
 
 5 <fc 6. Nummnlitic formation oi 
 Europe, Asia. <fec., p. 229. 
 
 6. Soissonnais Sands, or Lits Co- 
 quilliers, p. 228. 
 
 :1. Wanting in Paris basin, occurs 
 at Cassel, in French Flanders. 
 2. Argile Plasticine et Lignite, p. 
 229. 
 3. Lower Landenian of Belgium 
 in part ?, p. 235. 
 
 III. TERRAINS SECONDAIRES. 
 . TERRAINS CRETACEES. 
 
 9. Danien of P'OrLigny. 
 Calcaire pisolitique, near Paris, 
 
 p. 235. 
 
 Maestricht Beds, p. 237. 
 Coralline Limestone of Faxoe in 
 
 Denmark, p. 238. 
 10. Senonien, D'Orbigny. 
 Craie blanche avec si lex. 
 Obere Kreide of the Germans. 
 Upper Quadersandstein r of the 
 
 same. 
 
 La Scaglia of the Italians, 
 f Calcaire a hippurites, Pyrenees. 
 
 Turonien, D'Orbigny, or, Cnue 
 ! tnfeau of Touraine. 
 1 Craie argilense of some French 
 
 [ Uppcr^Wnerkalk of Saxony, 
 f Gres vert sup6rieur. 
 1 Glauconie crayeuse. 
 
 Craie chlorit^e. 
 
 Cenomanien, D'Orbigny. 
 
 Lower Quadersandstein of the 
 Germans. 
 
106 
 
 TABULAR VIEW OF FOSSILIFEROUS STRATA. [CH. ix. 
 
 Periods and Groups 
 13. GAULT. 
 
 British Examples. 
 Dark Blue Marl, Kent, p. 250. 
 Folkestone Marl or Clay. 
 Blackdown Beds, green sand an 
 (. chert, Devonshire, p. 251. 
 
 Foreign Equivalents and Synonym*, 
 
 Ores vert superieur 
 
 f Ores 
 
 j Glaue 
 
 d 1 Albie 
 
 (. Lowe 
 
 come crayeu 
 bien, D'Orbigny. 
 wer Planer of Saxc 
 
 in part. 
 
 LOWER CRETACEOUS, OR NEOCOMIAN. 
 
 LOWER 
 GREENLAND, 
 
 15. WEALDEX 
 (Weald Clay and 
 Hastings Sand). 
 
 F. OOLITE. 
 
 UPPER OOLITE. 
 
 16. PURBECK BEDS. 
 
 17. PORTLAND 
 
 BEDS. 
 
 18. KIMMERIDGE 
 CLAY. 
 
 Sand with green matter, Weald 
 
 of Kent and Sussex, p. 257. 
 Limestone (Kentish Rag,) p. 257. 
 Sands and clay with calcareous 
 
 concretions and chert. 
 Atherfield, Isle of Wight, p. 257. 
 
 Speeton Clay, Yorkshire. (. 
 
 Clay with occasional bands of f 
 limestone. -Weald of Kent, Sur- 
 rey, and Sussex, p. 260. j Formation Waldienne 
 
 Sand with calcareous grit and 1 NSocomien inferieur. 
 
 Gres vert infe'rieur. 
 Nfiocomien supSrieur. 
 Aptien, D'Orbigny. 
 Hils-conglomerat of Germany. 
 
 Hils-thon of Brunswick. 
 
 clay, Hastings, 
 Sussex, p. 262. 
 
 Cuckfield, ! 
 I 
 
 F. TERRAINS JURASSIQUES, 
 in part. 
 
 C Upper, Middle, and Lower Pnr- C Serpulitenkalk of Dunker, and 
 < beck, Dorsetshire and Wilts, < associated beds of the North 
 ( pp. 293-296. 
 
 MIDDLE OOLITE. 
 
 19. CORAL-RAG. 
 
 30. OXFORD CLAY. 
 
 Portland stone and Portland sand, 
 p. 300. 
 
 Clay of Kimmeridge, Dorset- 
 shire, p. 300. 
 
 Calcareous grit. 
 
 ( German Walderformation. 
 Groupe Portlandien of Beudant. 
 
 Kimmeridgien, D'Orbigny. 
 
 Calcaire a gryph6es virgules, of 
 Thirria. 
 
 Argiles de Honfleur, E. de Beau- 
 mont et Dufresnoy. 
 
 Groupe corallien de Beudant. 
 
 1. Dark blue clay, Oxfordshire 
 and Midland counties, p. 304. 
 
 2. Calcareous concretionary lime- 
 stone with shells, called Kel- 
 loway Rock, p. 34. 
 
 LOWER OOLITE. 
 
 31. GREAT or BATH 
 OOLITE, 
 
 INFERIOR 
 OOLITE. 
 
 G. LIAS. 
 
 1. Cornbrash and Forest Marble, 
 Wiltshire, p. 305. 
 
 Oolite and Stonesfleld 
 -Bath, Stonesfleld, pp. 
 
 4 2. Great C 
 
 Slate, I 
 
 I 305-309. 
 
 33. 
 
 LIAS. 
 
 Fuller's Earth, near Bath, p. 314. 
 
 Calcareous freestone, and yellow 
 sands of Cetteswold Hills, 
 Gloucestershire, p. 314. 
 
 Dundry Hill, near Bristol, pp. 
 102, 314. 
 
 1. Upper Lias, p. 318. 
 
 2. Marl-stone, ibid. 
 
 3. Lower Lias, ibid. 
 
 1. Oxfordien snpSrieur, Thur- 
 mann. 
 
 2. Oxfordien inferieur, or Callo- 
 vien, D'Orbigny. 
 
 Bathonien of Omalius D'Hallov. 
 Grand Oolithe. 
 Calcaire de Caen. 
 
 Oolithe Inferieur. 
 
 Oolithe ferrugineux of Normandy. 
 
 Oolithe de Bayeux. 
 
 Bajocien of D'Orbigny. 
 
 G. TERRAINS JURASSIQUES, 
 in part. 
 
 1. Eiage sup6rieur du 
 Thirria. 
 
 Toarcien D'Orbigny. 
 
 2. Lias moye 
 
 >n 
 
 Lias, 
 
 3. Calcaire a gryphge arque. 
 
 Liasien, D'Orbigny. 
 gryphg 
 
 Sin6murien, D'Orbigny. 
 Coal-field near Richmond, Vir- 
 ginia, p. 30. 
 
 H. TRIAS. 
 
 (Upper New Red Sandstone.) 
 
 ZT. NOUTEAU GRES ROUGE. 
 
 3. UPPER TRIAS. 
 
 35. MIDDLE TRIAS 
 
 or 
 Muscliclkalk. 
 
 36. LOWER TRIAS. 
 
 f Saliferous and Gypseous sand- f 
 
 stones and shales of Cheshire, Keuper of the Germans. 
 \ pp. 333-336. \ Marnes irisees of the French. 
 
 Bone-bed of Axmouth, Devon, p. I Saliferien, D'Orbigny. 
 
 f f Muschelkalk of the Germans. 
 
 \ Wanting in England. \ $ g*$* grcmgjart 
 
 I I Conchylien, D'Orbigny (in part). 
 
 C Red and white sandstone of Lan- C Bunter-Sandstein of the Germans. 
 < cashire and Cheshire, pp. 336, < Gres bigarr6 of the French. 
 ( 337. ( Conchylien, D'Orbigny (in part). 
 
CH. IX.] TABULAE VIEW OF FOSSILIFEROUS STRATA. 
 
 107 
 
 Periods and Group*. British Examples. 
 
 IV. PRIMARY. 
 
 I. PERMIAN, 
 OR MAGXESIAX IJMESTONE. 
 
 87. 
 
 Foreign Equivalents and Synonym*. 
 IV. TERRAINS DK TRANSITION. 
 TERRAINS PALEOZOIQUES. 
 
 L CALCAIRE MAGNESIJBN. 
 
 (Lower New lied.) 
 
 PERMIAN, 
 
 or 
 
 MAGNESIAN 
 LIMESTONE. 
 
 1. Concretionary limestone of 
 Durham and Yorkshire, p. 351. 
 
 2. Brecciated limestone, ibid. 
 
 3. Fossiliferous limestone, p. 352. 
 
 4. Compact limestone, ibid. 
 
 5. Marl-Slate of Durham, p. 353. 
 
 6. Inferior sandstones of various 
 colors, N. of England, p. 354. 
 
 Dolomitic conglomerate, Bris- 
 tol, p. 354. 
 
 1. StinksteinofThnringia. 
 
 2. Rauchwacke, ibid. 
 
 3. Dolomit or Upper Zechstein. 
 
 4. Zechstein, p. 350. 
 
 5. Mergel or Knpfer-schiefer. 
 
 6. Rothliegendes of Thuringia. 
 
 Permian of Russia, p. 355. 
 Ores des Vosges of the French 
 (in part). 
 
 K. CARBONIFEROUS. 
 
 28. UPPER 
 
 CARBONIFEROUS 
 
 {1. Coal-measures, 
 shale with sea 
 West of Englan 
 Chapters 24 and 
 2. Millstone Grit, 
 
 29. LOWER 
 
 CARBONIFEROUS. 
 
 Coal-measures, sandstone and 
 seams of coal, 
 of England and Ireland, 
 -nd 25. 
 
 pp. 358, 359. 
 
 1. Mountain or Carboniferous 
 limestone, p. 403, tt sea. 
 
 2. Lower limestone shale, Men- 
 dips. Carboniferous slate, 
 Ireland. 
 
 Carbonaceous schist with Possi- 
 douomya Becheri, p. 409. 
 
 K. TERRAIN HOUILLIER. 
 
 Coal-fields of the United States, p. 
 387. 
 
 1. Calcaire carbonifere of the 
 
 French. 
 1. Bergkalk or Kohlenkalk of 
 
 the Germans. 
 1. Pentremite limestone, United 
 
 States, p. 410. 
 
 Eiesel-schiefer and Jungere 
 Grauwacke of the Germans, p. 
 409. 
 
 Gypseous beds and Encrinital 
 limestone of Nova Scotia, p. 
 
 L. DEVONIAN, 
 or OLD RED SANDSTONE. 
 
 30. 
 
 31. 
 
 UPPER 
 DEVONIAN. 
 
 LOWER 
 DEVONIAN, 
 
 Yellow sandstone of Dura Den, 
 
 Fife. p. 412. 
 White sandstone of Elgin, with 
 
 Telerpeton, ibid. 
 Red sandstone and conglomerate, 
 
 p. 414. 
 Upper and middle Devonian of 
 
 N. Devon, including Plymouth 
 
 limestone, pp. 420, *- lfe> - 
 
 Lower Devonian of N. Devon, 
 North Foreland, p. 424. 
 
 Arbroath paving-stone, pp. 412- 
 415. 
 
 Bituminous schists of Caithness, 
 . p. 418. 
 
 TERRAIN DEVONIEN. 
 
 VlEUX GRE3 ROUGE. 
 
 Russian Devonian, Upper part, p. 
 
 425. 
 Catskill Group, United States, p. 
 
 426. 
 
 Eifel Limestone, p. 424. 
 Limestone of Villmar, Ac., Nas- 
 
 1. Spirifer Sandstone and Slate of 
 
 Sandberger. p. 424. 
 Older Rhenish Greywacke of 
 
 Roemer, ibid. 
 Russian Devonian, Lower part, 
 
 p. 425. 
 
 jr. SILURIAN. 
 
 33. UPPER 
 
 SILURIAN. 
 
 32 a. MIDDLE SILURIAN. 
 (Beds of passage between 
 Upper and Lower Silurian.) 
 
 1. Upper Ludlow, p. 430. 
 
 2. Aymestry Limestone, p. 434. 
 
 3. Lower Lndlow, ibid. 
 
 4. Wenlock Limestone, p. 435. 
 
 5. Wenlock shale, p. 437. 
 
 ' Caradoc or May Hill Sandstone, f 
 
 if. TERRAIN SILURIEN. 
 
 New York division from the Up- 
 per Pentamerus to the Niagara 
 Group inclusive, p. 444. 
 
 Etages E. to H. of Barrande, 
 Bohemia. 
 
 p. 437. 
 
 I 
 
 elusive, p. 444. ' 
 
 33. 
 
 LOWER 
 SILURIAN. 
 
 ILlandeilo Flags and shale, p. 439. f New York groups from the Hud- 
 
 Bala Limestone and black slate, I son-River beds to the Calcifer- 
 
 p. 441. ! ous sandstone inclusive, p. 444. 
 
 Graptolite Schists, S. of Scotland. ! Etages and D. (Barrande), Bo- 
 
 Limestoue, Chair of Kildare, Ire- j hernia, 
 
 land. L Slates of Angers, Franee. 
 
 N. CAMBRIAN. 
 
 UPPER 
 CAMBRIAN. 
 
 35. LOWER 
 
 CAMBRIAN. 
 
 Lingula Flags, North Wales, p. 
 
 448. 
 Stiper Stones, Shropshire. 
 
 Lowest fossiliferous rocks of 
 Wicklow, in Ireland, p. 419. 
 
 Primordial zone of Barrande in 
 
 Bohemia, p. 450. 
 Alum Schists of Sweden, p. 451. 
 Potsdam Sandstone of United 
 
 States and Canada, p. 451. 
 Wisconsin and Minnesota lowest 
 
 fossiliferous rocks, p. 452. 
 
 
1 08 ABEIDGED TABLE OF FOSSILIFEROUS STEATA. [Cn. IX. 
 
 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. 
 
 21. GREAT OB BATH OOLITE. 
 
 22. INFERIOR OOLITE. 
 
 23. LIAS. 
 
 24. UPPER TRIAS. 
 
 25. MIDDLE TRIAS, or 
 MUSCHELKALK. 
 
 26. LOWER TRIAS. 
 
 POST-TERTIARY. 
 
 PLIOCENE. 
 
 MIOCENE. 
 
 EOCENE. 
 
 CRETACEOUS. 
 
 JURASSIC. 
 
 * a 
 
 
 
 9 o 
 
 
 JH 
 
 
 E-I o 
 
 
 
 Q 
 
 
 HH 
 
 O 
 
 
 N3 
 
 i ^ 
 
 O 
 H 
 & 
 
 i 
 
 
 W gj ^q 
 
 
 fr OQ 
 O C/2 
 
 1 i.j 
 
 
 TRIASSIC. 
 
 27. PERMIAN, or 
 MAGNESIAN LIMESTONE. 
 
 28. COAL-MEASURES. 
 
 29. CARBONIFEROUS 
 
 LIMESTONE. 
 
 30. UPPER j 
 
 31. LOWER j 
 
 32. UPPER J 
 
 33. LOWER ] 
 
 34. UPPER ; 
 
 35. LOWER ' 
 
 DEVONIAN. 
 
 SILURIAN. 
 
 CAMBRIAN. 
 
 PERMIAN. 
 
 C ARBONIPEROUS . 
 
 DEVONIAN. 
 
 SILURIAN. 
 
 CAMBRIAN. 
 
Oz. X.] PRINCIPLES OF CLASSIFICATION. 109 
 
 CHAPTER X. 
 
 CLASSIFICATION OF TERTIARY FORMATIONS POST-PLIOCENE GROUP. 
 
 General principles of classification of tertiary strata Detached formations scat- 
 tered over Europe Strata of Paris and London More modern groups 
 Peculiar difficulties in determining the chronology of tertiary formations In- 
 creasing proportion of living species of shells in strata of newer -rigin Terms 
 Eocene, Miocene, and Pliocene Post-Pliocene strata Recent or human period 
 Older Post-Pliocene formations of Naples, Uddevalla, and Norway Ancient 
 upraised delta of the Mississippi Loess of the Rhine. 
 
 BEFOR.E 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 con- 
 founded, 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 compared to the secondary 
 formations, and their position often suggesting tie idea of their having 
 been deposited in different bays, lakes, estuaries, 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 accurately 
 determined, were those occurring in the neighborhood of Paris, described 
 in 1810 by MM. Cuvier and Brongniart. They were ascertained to con- 
 sist of successive sets of strata, some of marine, others of freshwater 
 origin, lying one upon the other. The fossil shells and corals were per- 
 ceived to be almost all of unknown species, and to have in general a 
 near affinity to those now inhabiting warmer seas. The bones and skel- 
 etons of land animals, some of them of large size, and belonging to more 
 than forty distinct species, were examined by Cuvier, and declared by him 
 not to agree specifically, nor even for the most part generically, with any 
 hitherto observed 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 
 
110 PRINCIPLES OF CLASSIFICATION. [Cir. X, 
 
 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. 
 
 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 pe- 
 riod ; 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 se- 
 riously for some years the progress of classification. A more scrupu- 
 lous attention to specific distinctions, aided by a careful regard to the 
 relative position of the strata containing them, led at length to the con- 
 viction that there were formations both marine and freshwater of various 
 ages, and all newer than the strata of the neighborhood 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 testacea in these newer 
 beds were distinct from those of the blue clay, and that while some ot 
 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 neighborhood of Bourdeaux 
 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 super- 
 position was brought to bear in support of this opinion ; for other strata, 
 contemporaneous with those of Bourdeaux, were observed in one district 
 
CH. X.] OF TERTIARY FORMATIONS. Ill 
 
 (the Valley of the Loire), to overlie the Parisian formation, and in an- 
 other (in Piedmont) to underlie the Subapennine beds. The first exam- 
 ple 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 lacus- 
 trine formation, which constitutes the uppermost subdivision of the 
 Parisian group, extending continuously 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 sim- 
 ilar to those of Bourdeaux, 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 dis- 
 covery, 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 pur- 
 sued 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 principles, 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 be- 
 comes 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 com- 
 pared. If any are found containing the same or nearly the same organic 
 remains, and occupying the same relative position, they are regarded in 
 the light of contemporary annals. All such monuments are said to re- 
 late to one period, during which certain events occurred, such as the 
 formation of particular rocks by aqueous or volcanic agency, or the con- 
 tinued 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 propor- 
 tion 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 enriched 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 con- 
 necting links, into another. They also know that the difficulty of classi- 
 fication 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 al- 
 
112 PRINCIPLES OF CLASSIFICATION [Cn. X. 
 
 ternative than to avail themselves of such breaks as still remain, or of 
 every hiatus in the chain of animated 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 regular sequence of geological monuments, as boundary 
 lines between our principal groups or periods, even though the groups 
 thus established 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 pre- 
 sented by this want of continuity when we endeavor to settle the chrono- 
 logical relations of these deposits, another arises from the frequent 
 dissimilarity in mineral character of strata of contemporaneous 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, al- 
 though 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 pro- 
 duced, 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, con- 
 tain 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 substi- 
 tuted for another wholly dissimilar. It has also been shown that in 
 proportion as the age of a tertiary deposit is more modern, so is its 
 fauna more analogous to that now in being in the neighboring 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 chronological 
 arrangement of scattered deposits, where we cannot avail ourselves 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 calcare- 
 ous 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 
 
Ca X.] OF TERTIARY FORMATIONS. 113 
 
 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 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. Contemporaneousness 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 coun- 
 tries, 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 ter- 
 tiary 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 
 everywhere 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 consequently there may have been a more rapid 
 destruction and renovation of species in one part of the globe than 
 elsewhere. Considerations of this kind should undoubtedly put us on 
 our guard against relying too implicitly on the accuracy of this test ; 
 ye: it can never fail to throw great light on the chronological re- 
 lations 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 tendency 
 which prevails in the present state of nature to a uniform rate of simul- 
 taneous fluctuation in the flora and fauna of the whole globe. The 
 grounds of such a doctrine cannot be discussed here, and I have ex- 
 plained 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 
 ?ffected is rarely, if ever, confined to a limited space, or to one geograph- 
 
114 FOSSIL SHELLS. [On. JL 
 
 ical province of animals or plants, but affects several other surrounding 
 and contiguous provinces. In each of these, moreover, analogous alter- 
 ations of the stations and habitations 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 essen- 
 tially altered, the flora and fauna throughout the world will have been 
 materially 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 improba- 
 ble 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 dif- 
 ferent parts of the atmosphere and ocean is so free and rapid, that the 
 temperature of certain zones cannot be materially raised or lowered 
 without others being immediately affected ; and the elevation or dimi- 
 nution 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 remains, 
 the testacea or the shell-bearing mollusca are selected as the most useful 
 and convenient class for the purposes of general classification. 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 absolutely 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 discordance 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 abundant, in a fossil state, than plants, reptiles, or fish, 
 they are still rare when contrasted with shells, especially in the European 
 tertiary formations. 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 coexisted at particular eras of the past ; 
 and having thus identified strata formed in seas with others which origi- 
 nated 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 * 
 
CH. X.] FOSSIL SHELLS. 115 
 
 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 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 
 Bourdeaux and Touraine ; and the upper all those newer than the mid- 
 dle 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 endeavoring to find characters for each, ex- 
 pressive of their different degrees of affinity to the living fauna. With 
 this view, I obtained information respecting the specific identity 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 inde- 
 pendent researches, and by the study of a large collection of fossil and 
 recent shells, at very similar views respecting 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 identical with the recent which characterized 
 successive groups ; and this table, planned by us in common, was pub- 
 lished 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 tertiary strata, or those of London and Paris, there were 
 about 3i per cent of species identical with recent ; in the middle ter- 
 tiary 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 num- 
 ber of species identical with those now living was believed to be from 
 90 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 Xewer Pliocene. The first of the above terms, Eocene, is derived 
 from iju, eos, dawn, and xaivos, cainos, recent, because the fossil shells of 
 
 * See Pr-inc. of Geol. vol. iii. 1st ed. 
 
116 FOURFOLD DIVISION OF TERTIARY FORMATIONS. [On. X, 
 
 this period contain an extremely small proportion of living species, which 
 may be looked upon as indicating the dawn of the existing state of tha 
 testaceous fauna, no recent species having been detected in the older or 
 secondary rocks. 
 
 The term Miocene (from |ut.iov, meion, less, and xajvoj, cainos, recent) 
 is intended to express a minor proportion of recent species (of testacea), 
 the term Pliocene (from wXsfov, pleion, more, and xaivo, cainos, recent) a 
 comparative plurality of the same. It may assist the memory of stu- 
 dents to remind them, that the J/wcene contain a wmor proportion, and 
 Pliocene a comparative ^/urality 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 spe- 
 cies 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 conchological 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 men- 
 tioned were obtained in 1830 by M. Deshayes was as follows : 
 
 In the formations of the Pliocene periods, older and newer - 777 
 In the Miocene - 1021 
 
 In the Eocene - 123S 
 
 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 spe- 
 cies 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 reforms have 
 been called for in the classification first proposed. The Eocene, Miocene, 
 and Pliftcene periods have been made to comprehend certain sets of 
 strata of which the fossils do not always conform strictly in the propor- 
 tion 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 
 
Ca X.] POST-PLIOCEXE FORMATIONS. 117 
 
 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 ex- 
 tinct species. 
 
 These modern formations, thus defined, comprehend not only those 
 strata which can be shown to have originated since the earth was inhab- 
 ited by man, but also deposits of far greater extent and thickness, 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 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 accumu- 
 lated 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 sub- 
 terranean 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 fab- 
 ricated by the hands of man. 
 
 Thus at Puzzuoli, near Naples, marine strata are seen containing frag- 
 ments of sculpture, pottery, and the remains of buildings, together with 
 innumerable shells retaining in part their color, and of the same species 
 as those now inhabiting the Bay of Baiae. The uppermost of these 
 beds is about 20 feet above the level of the sea. Their emergence can 
 be proved to have taken place since the beginning of the sixteenth cen- 
 tury.* Now here, as in almost every instance where any alterations of 
 level have been going on in historical periods, it is found that rocks contain- 
 ing shells, all, or nearly all, of which still inhabit the neighboring 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 Na- 
 ples, the post-pliocene strata, consisting of clay and horizontal 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 not accom- 
 panied 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 
 
 * See Principles, Index, " Serapis." 
 
118 POST-PLIOCENE FORMATIONS. [On. X. 
 
 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 w r e 
 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 or 
 marine and volcanic formations, Dr. Philippi collected in the stratified 
 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, interstratified in 
 some parts with marl, and here and there with great beds of solid lava. 
 Visconti ascertained by trigonometrical measurement 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 declivity of the mountain, I collected, in 
 1828, many shells of species now inhabiting the neighboring 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 regions surrounding the Bay of Baise, 
 although none of them extinct, indicate a slight want of correspondence 
 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 Mediterranean. 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 ; and Ostrea la- 
 mellosa, 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 thick 
 ness, "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 insensible tc 
 the inhabitants, being only ascertainable by careful scientific measure- 
 ments compared after long intervals. Such an upward movement 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 
 
 * Geol. Quart. Journ. vol. il Memoirs, p. 15. 
 
CH. X.] RECENT STRATA IN SWEDEN. 119 
 
 W., the amount of elevation always increasing as we proceed toward? 
 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. Accordingly, 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 de- 
 tected various works of 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 neighborhood of these 
 recent strata, both to the northwest 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-plio- 
 cene 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 characterizing 
 these upraised sands and clays consists exclusively of existing northern 
 species of testacea, yet, according to Loven (an able living naturalist of 
 Norway), the species do not constitute such an assemblage as now in- 
 habits 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 abundance, 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 
 
 * Quart. GeoL Journ. 4 Mems. p. 48 
 
120 KECENT AND POST-PLIOCENE FORMATIONS. [Cii. X 
 
 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 ex- 
 perienced 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 of the 
 world, of the bed of the sea, and the adjoining coast, having been up- 
 lifted 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 neighboring mainland, he found other signs cor- 
 roborating 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 probability 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 skeletons. 
 The stone is extremely hard, and chiefly composed of comminuted 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 Havana, and in other islands, in 
 which af : shells identical with those now living in corresponding lati- 
 tudes ; some well-preserved, others in the state of casts, all referable to 
 the post-pliocene period. 
 
 I have already described in the seventh chapter, p. 84, what would be 
 the effects 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 occurred in the post- 
 pliocene era in 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 
 
 * Journal, p. 451. 
 
CH. X.] PLAIN OF THE MISSISSIPPI. 121 
 
 same rate at which its foundations sink, so that these may go down hun- 
 dreds or thousands of feet perpendicularly, and yet the sea bordering the 
 delta may always be excluded, the whole deposit continuing to be terres- 
 trial 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.* 
 Should these countries be once more slowly upraised, the rivers would 
 carve out valleys through the horizontal and unconsolidated strata as they 
 rose, sweeping away the greater portion of them, and leaving mere frag- 
 ments in the shape of terraces skirting newly-formed alluvial 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 Natchez 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 neighboring forests and swamps. In 
 the same loam also are found the bones of the Mastodon, Elephant, Mega- 
 lonyx, and other extinct quadrupeds.f 
 
 I have endeavored to show that the deposits forming the delta and 
 alluvial plain of the Mississippi consist of sedimentary matter, extend- 
 ing 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 as- 
 certaining 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 an- 
 tiquity, amounting to many tens of thousands of years to the existing 
 delta, the origin of which is nevertheless an event of yesterday when con- 
 trasted with the terraces formed of the loam above mentioned. The ma- 
 terials of the bluffs were produced during the first part of a great oscilla- 
 tion 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.^ 
 
 Loess of the Valley of the Rhine. A similar succession of geograph- 
 ical changes attended by the production of a fluviatile formation, singu- 
 larly resembling that which bounds the great plain of the Mississippi, 
 seems to have occurred in the hydrographical basin of the Rhine, since 
 
 * See Principles, 8th ed. pp. 260-268, 9th ed. 257-280. 
 
 f See Principles of GeoL 9th ed., and Lyell's Second Visit to the United States, 
 vol. ii. p. 257. 
 
 Lyell's Second Visit to the United States, vol. ii. chap. 34. 
 
122 LOESS OF THE VALLEY OF THE KHINE. [Cn. X. 
 
 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 gray color, consisting chiefly of argillaceous 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 nod- 
 ules, 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 mass, except here and there at the 
 bottom, where there is occasionally a slight intermixture of drifted ma- 
 terials derived from subjacent rocks. Unsolidified as it is, and of so 
 perishable a nature, that every streamlet flowing over it cuts out for 
 itself a deep gully, it usually terminates in a vertical cliff, from the sur- 
 face 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 homogeneous as generally to exhibit no signs of 
 stratification, owing, probably, 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 deposi- 
 tion, where coarser and finer materials alternate, especially near the bot- 
 tom. Calcareous concretions, also inclosing land-shells, are sometimes 
 arranged in horizontal layers. It is a remarkable deposit, from its posi- 
 tion, wide extent, and thickness, its homogeneous mineral composition, 
 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 de- 
 posited during river inundations ; and it is also clear that similar mud 
 and silt were thrown down contemporaneously in the valleys of the prin- 
 cipal tributaries of the Rhine. 
 
 Thus, for example, it may be traced far into Wiirtemberg, up the val- 
 ley 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, between 
 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 plane of the Rhine near Freiburg, has been covered almost every- 
 where with this loam, as have the extinct volcanoes between Coblentz 
 and Bonn. Near Andernach, in the Kirchweg, the loess containing the 
 usual shells alternates with volcanic matter ; and over the whole are 
 strewed layers of pumice, lapilli, and volcanic sand, from 10 to 15 feet 
 thick, very much resembling the ejections under which Pompeii lies 
 buried. There is no passage at this upper junction from the loess into 
 
CH. X.] LOESS OF THE RHINE. 123 
 
 the pumiceous superstratum ; 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 con- 
 cretions. 
 
 The interstratification above alluded to, of loess with layers of 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 volcanoes, and spread them out occasionally over the yellow 
 loam. Sometimes, also, the melting of snow on the slope of small vol- 
 canic 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 examining 
 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 oft' large branches up the course of 
 the Main, ISTeckar, 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 phe- 
 nomena ; 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 re- 
 quire 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 above the sea. It would be necessary, moreover, to 
 place this lofty barrier somewhere below Cologne, or precisely where the 
 level of the land is now lowest. 
 
 Instead, therefore, of supposing one continuous lake of sufficient extent 
 
124 LOESS OF THE RHINE [Cn. X. 
 
 and depth to allow of the simultaneous accumulation of the loess, at various 
 heights, throughout the whole area where it now occurs, I formerly suggest- 
 ed that, subsequently to the period when the countries now drained by the 
 Rhine and its tributaries had nearly acquired their actual form and geo- 
 graphical features, they were again depressed gradually by a movement 
 like that now in progress on the west coast of Greenland.* In propor- 
 tion as the whole 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 gradually. 
 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 s*nd remarkable ho- 
 mogeneousness of composition and fossils, attest the ancient continuity 
 and common origin of the whole. By imagining these oscillations of 
 level, we dispense with the necessity of erecting and afterwards removing 
 a mountain barrier sufficiently 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 Buli- 
 mus, is very large in the loess ; but in many places aquatic species of 
 the genera Lymnea, Paludina, and Planorbis are also found. Thesf; 
 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 favor 
 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 another species, S. amphibia 
 (fig. 34, p. 29). Among other abundant fossils are Helix plebeia and 
 Pupa mvscorum. (See Figures.) Both the terrestrial and aquatic she-lls 
 preserved in the loess are of most fragile and delicate structure, and yet, 
 
 Fig. 106. Fig. 107. Fig. 108. 
 
 Succinea elongata. Pupa muscorum. Helix plebeia. 
 
 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 color of some of the land-shells, as that of Helix nevioralis, is 
 occasionally preserved. 
 
 * Princ. of Geol. 3d edition, 1834, vol. iii. p. 414. 
 
Ca X.] AND ITS FOSSILS. 125 
 
 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 ver- 
 tebrae, 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 fam- 
 ily ascend the Senegal, Amazon, and other great rivers, to the distance 
 of several hundred miles from the ocean.* 
 
 At Cannstadt, near Stuttgardt, in a valley also belonging to the hydro- 
 graphical basin of the Rhine, I have seen the loess pass downwards into 
 beds of calcareous tuff and travertin. Several valleys in northern Ger- 
 many, as that of the Hm 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, P>aludina, &c., from 50 to 80 
 feet thick, with a bed of loess much resembling that of the Rhine, occa- 
 sionally incumbent on them. In these modern limestones used for build- 
 ing, the bones of Elephas primigenius. Rhinoceros tichorinus, Ursus, 
 spelceus, Hycena spelcea, with the horse, ox, deer, and other quadrupeds, 
 occur; and in 1850 Mr. H. Credner and I obtained in a quarry at Ton- 
 na, 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 European 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-excava- 
 tion of the valleys ; an operation which doubtless consumed a long period 
 of time, since which the mammiferous fauna has undergone a considerable 
 
 * Proceedings of Geol. Soc. No. 43, p. 222. 
 
126 BOULDER FORMATION. [On. XL 
 
 CHAPTER XL 
 
 NEWER PLIOCENE PERIOD BOULDER FORMATION. 
 
 Drift of Scandinavia, northern Germany, and Russia 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 
 Norfolk Associated freshwater deposit Bent and folded strata lying on un- 
 disturbed 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 consists of mud, 
 sand, and clay, sometimes stratified, but often wholly devoid of stratifica- 
 tion, 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 gen- 
 erally contains numerous fragments of rocks, some angular and others 
 rounded, which have been derived from formations of all ages, both fos- 
 siliferous, volcanic, and hypogene, 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 increas- 
 ing as we advance northwards. 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 
 neighboring rocks ; so that it is red in a region of red sandstone, white in 
 a chalk countiy, and gray 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 perma- 
 nently retaining any superficial markings which may have been imprinted 
 upon it, is usually smoothed or polished, and exhibits parallel striae 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 angular and rounded stones have travelled. 
 
CH. XI.] KOCKS DEIFTED BY ICE. 127 
 
 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 strise are made on 
 
 Fi. 109. 
 
 Limestone polished, farrowed, and scratched by the glacier of Kosenlaui, in Switzerland. (Agassiz.) 
 
 a a. "White streaks or scratches, caused by small grains of flint frozen into the ice. 
 & &. Furrows. 
 
 the polished surface by crystals or projecting edges of the hardest min- 
 erals, 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 
 01 Denmark, has been observed by Dr. Forchhammer, and helps us to 
 conceive how large icebergs, 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 circumfer- 
 ence. Many of them were loaded with beds of earth and rock, of such 
 thickness that the weight was conjectured to be from 50,000 to 100,000 
 tons.* A similar transportation of rocks is known to be in progress in 
 the southern hemisphere, where boulders included in ice are far more 
 frequent than in the north. One of these icebergs was encountered in 
 1839, in mid-ocean, in the antarctic regions, many hundred miles from 
 any known land, sailing northwards, with a large erratic block firmly 
 
 * Voyages in 1822, p. 233. 
 
128 ORIGIN OF TILL. [CH. XI. 
 
 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 float- 
 ing 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 arid 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 float- 
 ing 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 mechan- 
 ical power they might exert when fairly set in motion must be prodigious.'* 
 A large proportion of these floating masses of ice is supposed not to be de- 
 rived from terrestrial glaciers, f 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 ar- 
 ranged 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 intercalations 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 outstanding 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 collec- 
 tion 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 submerged, 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 sea- 
 ward 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 
 * T. L. Hayes, Boston Journ. Nat. Hist. 1844. f Principles, ch. xv. 
 
CH. XL] STRATA CONTAINING RECENT SHELLS. 129 
 
 have been carried southward cannot be doubted ; those of granite, for 
 example, scattered over large districts of Russia and Poland, agree pre- 
 cisely 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 direction having been from 
 N. W. to S. K, or from the Scandinavian mountains over the seas and 
 low lands to the southeast. That its accumulation throughout this area 
 took place in part during the post-pliocene period is proved by its super- 
 position 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 miles, consisted of horizontal strata, full of shells similar 
 to those now inhabiting the arctic sea, on which rested the boulder forma- 
 tion, containing large erratics. 
 
 In Sweden, in the immediate neighborhood of Upsala, I had observed, 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 spe- 
 cies, intermixed with some proper to freshwater. The marine shells arc 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 
 neighboring gulf was already characterized by its peculiar fauna.* Here, 
 therefore, we. have proof that the transport of erratics continued to take 
 place, not merely when the sea was inhabited by the existing 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 associated 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 
 
 * See paper by the author, Phil. Trans. 1835. p. 15. 
 
130 
 
 FOSSILS OF ARCTIC SPECIES. 
 
 XI 
 
 -ariable 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 prevailing 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 di- 
 visional planes or "joints," which cause them to split when weathered. 
 Hence as often as they start on a fresh voyage, becoming 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) of several trains of huge 
 erratics in lat. 42 50' IS", in the United States, in Berkshire, on the west- 
 ern confines of Massachusetts, has convinced me that this cause has been 
 very influential both in reducing the size of erratics, and in restoring an- 
 gularity 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 Caith- 
 ness, 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 
 
 Fig. 110. 
 Astarte borealis. 
 
 Fig. 111. 
 Leda oblong a. 
 
 Fig. 112. Fig. 113. Fig. 114. Fig. 115. 
 
 Saxicava rugosa. Pecten i&landicus. Natica clausa. Troplion clathratum. 
 
 Northern shells common in the drift of the Clyde, in Scotland. 
 
 been traced in it as high as 554 feet above the sea. Although a proper 
 tfion 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 
 
CH. XL] NORFOLK DRIFT, ETC. 131 
 
 now inhabit more northern seas, where we may, perhaps, hereafter find 
 living representatives 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, favors the idea that ice-rafts rather than gla- 
 ciers were in general the transporting agents. The Grampians in For- 
 farshire 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 Strath- 
 more. 
 
 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 for- 
 mation being 50 miles distant.f 
 
 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 contrary, 
 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 formation 
 displays almost everywhere, in its mineral ingredients, a strange hetero- 
 geneous mixture of the mins of adjacent lands, with stones both angular 
 and rounded, which have come from points often very remote. Thus we 
 find it in our eastern counties, as in Norfolk, Suffolk, Cambridge, Hunt- 
 ingdon, 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 
 
 * See above, section, p. 48. f Geol. of Fife, <fcc. p. 220. 
 
132 
 
 NORFOLK DRIFT AND 
 
 [Cn. Xi 
 
 drift is wanting, as, for example, in the Wealds of Surrey, Kent, and 
 Sussex. 
 
 Norfolk drift. The drift can nowhere be studied more advantageous- 
 ly in England than in the cliffs of the Norfolk coast between Happisburgh 
 and Croiner. 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 substituted 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. Peb- 
 bles, together with some large boulders of granite, porphyry, green- 
 stone, 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 continuous stream of blocks from Norway and Sweden to Den- 
 mark, and across the Elbe, through Westphalia, to the borders of Hol- 
 land. 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 positively 
 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 
 
 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 vege 
 
 Fig. 117. 
 
 Paludina marginata, Michaud. (P. minuta, Strickland.) 
 The middle figure is of the natural size. 
 
CH. XL] 
 
 ASSOCIATED FRESHWATER STRATA. 
 
 133 
 
 table matter, and are divided into thin layers. The imbedded shells be- 
 long to the genera Planorbis, Lymnea, Paludina, Uhio, Cyclas, and 
 others, all of British species, except a minute Paludina, now inhabiting 
 France. (See fig. 117.) 
 
 The Cyclas (fig. 118) is merely a remarkable variety of the common 
 English species. The scales and teeth of fish of the genera Pike, Perch, 
 
 Fig. 118. 
 
 Cyclas (Pisidiwri) amnica, var. ? 
 The two middle figures are of the natural size. 
 
 Roach, and others, accompany these shells ; but the species are not con- 
 sidered 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 stra- 
 tum 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 over- 
 lying boulder formation have often undergone 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 annexed section (fig. 119) represents a cliff about 
 
 Fig. 119. 
 
 Gravel 
 
 Cliff 50 feet high between Bacton Gap and Mundesley. 
 
 50 feet high, at the bottom of which is till, or unstratified clay, contain- 
 ing boulders having an even horizontal surface, on which repose con- 
 formably 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 colored beds of loose sand, loam, and pebbles 
 
134: 
 
 MASSES OF CHALK IN DKIFT. 
 
 [Cn. XI, 
 
 are so complicated that not only may we sometimes find portions of 
 them which maintain their verticality to a height of 10 or 15 feet, but 
 they have also been folded upon themselves in such a manner that con- 
 tinuous layers might be thrice pierced in one perpendicular boring. 
 
 At some points there is an apparent folding of the beds round a cen 
 tral nucleus, as at a, fig 120, where the strata seem bent round a small 
 
 Fig. 121 
 
 Fig. 120. 
 
 Folding of the strata between East 
 and West Kunton. 
 
 Section of concentric beds west of Oromer. 
 
 1. Blue clay. 8. Yellow Sand. 
 
 2. White sand. 4. Striped loam and clay. 
 
 5. Laminated blue clay. 
 
 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 sur- 
 face. 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 diameter. One striking in- 
 stance 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.) 
 
 This chalky fragment is only one of many detached masses which have 
 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.* 
 
 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 answered that, it 
 
 * For a full account of the drift of East Norfolk, see a paper by the author 
 Phil. Mag. No. 104, May, 1840. 
 
On. XI.] 
 
 MASSES OF CHALK IN DRIFT. 
 Fig. 122. 
 
 135 
 
 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. 
 
 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 strand- 
 ing of ice-islands. We learn from the observations of Messrs. Dease and 
 Simpson in the polar regions, that such islands, when they run aground, 
 push before them large mounds of 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 sub- 
 merged banks, the inferior portions of the same remaining unmoved. 
 Or many of the complicated curvatures 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, together 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 associa- 
 ted 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 con- 
 glomerate of sand or shingle, and, as Mr. Trimmer has suggested,* alter- 
 nate layers of earthy matter may have sunk down slowly during the lique- 
 faction of the intercalated ice, so as to assume the most fantastic 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 frequently find 
 that the foundation, consisting of peat and shell-marl, or of quicksand 
 and mud, gives way, and sinks as fast as the embankment is raised at the 
 top. At the same time, there is often seen at the distance of many yards, 
 in some neighboring part of the morass, a squeezing up of pliant strata, 
 the amount of upheaval depending on the volume and weight of rnate- 
 
 * Quart. Journ. Geol. Soc. vol. vii. p. 22. 
 
136 BUKIED FOEEST IN NORFOLK. [Cn. XL 
 
 rials heaped upon the embankment. In 1852 I saw a remarkable in 
 stance 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 es- 
 tuary 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. Mean- 
 while the adjoining bottom of the estuary, supporting a dense growth of 
 salt-water plants, only visible at low tide, had been pushed gradually up- 
 ward, 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 fusca, Nassa obsoleta, Natica 
 triseriata, and others. In some of these curved beds the layers of shells 
 were quite vertical. The upraised area was 75 feet wide, and several hun- 
 dred yards long. Were an eqaal load, melted out of icebergs or coast-ice 
 thrown down on the floor of a sea, consisting of soft mud and sand, similai 
 disturbances 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 superimposed. 
 
 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 Nor- 
 folk 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 Lanca- 
 shire, Cheshire, Shropshire, Staffordshire, and Worcestershire, contains 
 in some places marine shells of recent species, rising to various heights, 
 from 100 to 350 foot 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 altitude. 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 neighborhood where there is evi- 
 dence 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 
 
CH. XII.] FOSSIL REMAINS IX DRIFT. 137 
 
 Isles of sub-aerial glaciers. Dr. Buckland published in 1842 his reasons foi 
 bolievinor that the Suowdoniau mountains in Caernarvonshire were former- 
 
 O 
 
 ly covered with glaciers, which radiated 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. 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 sometimes 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 re- 
 mains 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 inhabited 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. 155) and Turritella 
 incrassata (a crag fossil) ; also a southern form of Fusus, and a Mitra 
 allied to a Spanish species.* 
 
 CHAPTER XH. 
 
 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 Me- 
 teorite 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 remains, leading us to 
 refer its origin to a modern period. If, then, we encounter so much dif- 
 ficulty 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 ob- 
 scurity the student may ask, not without reasonable alarm, how we can 
 hope to decipher the records of remoter ages. 
 
 * Forbes, Memoirs of Geol. Survey of Great Britain, voL i. p. 377. 
 
138 GLACIAL PHENOMENA [Ca Xll 
 
 To remove from the mind as far as possible this natural feeling oi 
 discouragement, I shall endeavor 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 
 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 boul- 
 der 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 earthquakes, or 
 by the sudden upheaval of land from the bed of the sea, had swept over 
 the continents, carrying with them vast masses of mud and heavy 
 stones, and forcing these stones over rocky surfaces so as to polish and 
 imprint upon them long furrows and stria3. 
 
 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 ex- 
 tension 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 transportation of stony frag- 
 ments to great distances, and the striation, polishing, and grooving of 
 solid floors of rock, are here again intimately connected with accumula- 
 tions 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 Mediter- 
 ranean ; 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 encounter 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 
 
Cn. XIL] OF NORTHERN ORIGIN. 139 
 
 considerably colder than now during the period under consideration, 
 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 en- 
 tire modification which extreme cold would produce in the operation of 
 those causes spoken of in the sixth chapter as most active in the forma- 
 tion 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 sub- 
 marine bottom, whether on mountain tops or in low plains, with scarcely 
 any relation to the inequalities 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 asso- 
 ciated 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 mercenaries 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 isother- 
 mal 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. 
 
140 
 
 DKIFT SHELLS IN CANADA. 
 
 [CE. XII 
 
 Another resemblance between the distribution of the drift fossils in 
 Europe and North America has yet to be pointed out. In Norway, 
 Sweden, and Scotland, as in Canada and the United States, the marine 
 shells are confined to very moderate elevations above the sea (between 
 100 and TOO feet), while the erratic blocks and the grooved and pol- 
 ished 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 neighborhood 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 Ine 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, 
 
 ' Fig. 123. 
 
 K. Mr. KylarnVs house. 
 
 h. Clay and sand of higher grounds, with 
 
 Kaxicava, &c. 
 g. Gravel with boulders. 
 / Mass of Saxicava rugosa, 12 feet thick, 
 c. Sand and loam with Mya, truncata, 
 
 Scalaria Cfrcenlandica, &c. 
 
 d. Drift, with boulders of syenite, &c. 
 
 c. Yellow sand. 
 
 &. Laminated clay, 25 feet thick. 
 
 A. Horizontal lower Silurian strata. 
 
 B. Vallev re-excavated. 
 
 which will give an idea of the general position of 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, c?, e, /, 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 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 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 color. This shelly 
 deposit, containing Saxicava rugosa and other characteristic marine shells, 
 
 * Geol. Trans. 2d series, vol. vi. p. 1 35. Mr. Smith of Jordanhill had arrived at 
 limilar conclusions as to climate from the shells of the Scotch Pleistocene deposits, 
 f Proceedings of Geol. Soc. No. 63, p. 119. 
 
CH. XIL] SUBSIDENCE IX DRIFT PERIOD. 
 
 Fig. 124. 
 
 a 
 
 Astarte Laurentiana. 
 a. Outside. &. Inside of right valve. c. Left valve. 
 
 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 submergence 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 de- 
 tritus or size of the rocky fragments swept along by it, could produce 
 such long, perfectly straight and parallel furrows, as are everywhere visi- 
 ble in the Niagara district, and generally in the region north of the 40th 
 parallel of latitude.f 
 
 By the hypothesis of such a slow and gradual subsidence of the land 
 we may account for the fact that almost everywhere in IS". 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 depres- 
 sion 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 occa- 
 sional icebergs, might be sunk to a depth of several hundred fathoms. By 
 the constant depression 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 
 
 * Travels in IS". America, vol. ii. p, 141. f Ibid. p. 99, chap. xix. 
 
142 STRIATED PEBBLES AND BOULDERS. [Ca XII. 
 
 to a depth scarcely, if at all inhabited by testacea and zoophytes. Mean- 
 while, during the formation of the unstratified and unfossiliferous mass in 
 deeper water, the smoothing 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 re- 
 converted 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 re- 
 arranged 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 fossiliferous ; secondly, an unstratified and unfossilifer- 
 ous mass, called till, for the most part of much older date than the pre- 
 ceding, 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 independent 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 striae, 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 preserve 
 organic remains may, perhaps, be owing, as already hinted, to the 
 
 * Bulletin Soc. Gol. de France, torn, iv 2de ser. p. 1121. 
 
CH. XII.] MASTODON GIGANTEUS. 143 
 
 absence of testacea in the deep sea, where the undisturbed accumulation 
 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 vegeta- 
 tion 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 unin- 
 habitable, 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 Ice- 
 land 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 gradually, 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 gla- 
 cial epoch, there would be an intimate association of transported matter 
 of northern origin with fossil-bearing sediment, whether marine or fresh- 
 water, 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 ex- 
 amined one of these spots at Geneseo in the state of New York, from 
 which the bones, skull, and tusk of a Mastodon 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 consisted of several species of Lymnea, of Pla- 
 norbis 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 vegetable matter were extracted, 
 
144 EXTINCT MAMMALIA ABOVE DRIFT. [On. XIL 
 
 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 it? 
 height 12 feet. The anchylosing of the last two ribs on the right side 
 afforded Dr. John C. Warren a true gauge for the space occupied 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 ascer- 
 tained by analysis, to 27 per cent., so that when all the earthy ingre- 
 dients 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 quadru- 
 peds were mired in modern times, unless we use that term strictly in a 
 geological sense. I have shown that there is a fluviatile deposit 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 freshAvater 
 gravel which incloses it is decidedly of much more modern origin than 
 the drift or boulder clay of the same region/ 7 ' 
 
 Other extinct animals accompany the Mastodon giganteus in the post- 
 glacial deposits of the United States, among which the Castoroides ohi- 
 oensis, Foster and Wyman, a huge rodent allied to the beaver, and the 
 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. 
 
 * See Travels in N. America, vol. i. chap, ii., and Principles of Geol. chap xiv. 
 
OH. XII] CLIMATE OF DEIFT PERIOD. 145 
 
 It appears clear, however, from what we know of the tertiary fossils oi 
 Europe and I believe the same will hold 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 Elephas primigenius and Rhinoceros tichorinus 
 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 south- 
 ern, hemisphere at the time when the Scandinavian, British, and Alpine 
 erratics were transported into their present position. It must not be for- 
 gotten that a great deposit of drift and erratic blocks is now in full pro- 
 gress 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 uneven 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 conti- 
 nent, 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 Eng- 
 land. 
 
 Not only are these operations going on between the 45th and 60th 
 parallels of latitude south of the line, while the corresponding zone oi 
 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 forests, as in Terra del Fuego. There is here no difference of lati- 
 tude 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 enumerated the countless icebergs which float 
 from the antarctic zone, and which chill, as they melt, the waters of the 
 ocean, and the surrounding air, which they fill with dense fogs. 
 
 I have endeavored in the " Principles of Geology," chapters 7 and 8, 
 to point out the intimate connection of climate and the physical geogra- 
 phy 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 
 
 10 
 
146 ALPINE ERRATICS. [CH. XIT 
 
 mountains of Scandinavia, Scotland, and Switzerland, may have been 
 less elevated than at present. But if in both of the polar regions a 
 considerable area of elevated dry land existed, such a concurrence of re- 
 frigerating conditions in both hemispheres might have created for a time 
 an intensity 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 attention, not only 
 from their magnitude, but because they lie beyond the ordinary limits ot 
 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 appear- 
 ances which have been so often alluded to, as distinguishing or accom- 
 panying the drift, between the 50th and 7 Oth 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 excursions 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 surrounding 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, light- 
 ning, 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 
 nd of the ice being called terminal moraines. Such heaps of earth and 
 
 * Agassiz, Eludes sur les Glaciers, and Syst6me Glaciere. 
 
Cn. XII.] MORAINES OF GLACIERS. 147 
 
 boulders every glacier pushes before it when advancing, and leaves 
 behind it when retreating. When the Alpine glacier reaches a lower 
 and warmer situation, about 3000 or 4000 feet above the sea, it melts 
 so rapidly tjiat, 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. 
 Yenetz, 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 gla- 
 cier leaves behind it as it retrogrades, and among these the most promi- 
 nent, as before stated, are the terminal moraines, or mounds of tmstrati- 
 fied earth and stones, often divided by subsequent floods into hillocks, 
 which cross the valley like ancient earth-works, or embankments 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 intersect 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 oblitera- 
 tion ; 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 
 
148 ALPINE ERRATICS. [On. XII 
 
 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 stones scoop out grooves in it. 
 Another effect also of this action, not yet adverted to, is called " roches 
 moutonnees." Projecting eminences 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 protected by a cov- 
 ering of clay or turf, these marks of abrasion seem capable of enduring 
 forever. They have been traced in the Alps to great heights above the 
 present glaciers, and to great horizontal distances 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 sum- 
 mit 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 situa- 
 tion 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 enu- 
 merated, the moraines, erratics, polished surfaces, domes, stria3, cal- 
 drons, 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 every- 
 where 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 phenom- 
 enon which has astonished and perplexed the geologist for more than 
 half a century. No conclusion can be more incontestable than that these 
 
Cii. XIL] ON THE JURA. 149 
 
 angular blocks of granite, gneiss, and other crystalline formations, came 
 from the Alps, and that 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 cottages ; 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 Neufchatel, and is no less than 40 feet in diameter. 
 
 It will be remarked that these blocks on the Jura offer an exception 
 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 Box, 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 Bernese Ober- 
 land ; and those on the eastern Jura from the Alps of the small cantons, 
 Glaris, Schwytz, Uri, and Zug. The blocks, therefore, 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 frag- 
 ments, except near their confines, was always regarded as most enig- 
 matical 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 
 labors under this difficulty, that the difference of altitude, when distributed 
 over a space of 50 miles, gives an inclination of no more than two de- 
 grees, 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. 
 
 * Archiac, Hist, des Progrds, <fec. vol. ii. p. 249. 
 
150 EEEATICS OF THE JUEA. [On. XII 
 
 In the theory which I formerly advanced, jointly with Mr. Darwin,* 
 it was suggested that the erratics may have been transferred by floating 
 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,f 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 another place angular blocks of syenite were met with. Their 
 arrangement 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 trans- 
 ported 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 the 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.J; 
 
 * See Elements of Geology, 2d ed. 1841. f Darwin's Journal, p. 283. 
 
 \ More recently Sir R. Murchison, having revisited the Alps, has declared his 
 
OH. XII] METEORITES IX DRIFT. 151 
 
 Meteorites in drift. Before concluding my remarks on the northern 
 drift of the Old World, I shall refer to a fact recently announced, the 
 discovery of a meteoric stone at a great depth in the alluvium of North- 
 ern Asia. 
 
 Erman, in his Archives of Russia for 1841 (p. 314), cites a very cir- 
 cumstantial 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 we : ghing 17 J pounds, of a 
 steel-gray color, somewhat harder than ordinary iron, and, on analyzing 
 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 auriferous 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 combi- 
 nations, the water and mud being charged with chloride of sodium and 
 other salts. We find that anchors, cannon, and other cast-iron imple- 
 ments which have been buried for a few hundred years oft" our English 
 coast have decomposed in part or entirely, turning the sand and gravel 
 which inclosed them into a conglomerate, cemented together by oxide of 
 iron. In like manner meteoric iron, although its rusting would be some- 
 what checked by the alloy of nickel, could scarcely ever fail to decompose 
 in the course of thousands of years, becoming oxide, sulphuret, or car- 
 bonate 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 hope- 
 less than we might have anticipated. 
 
 opinion that " the great granitic blocks of .Mont Blanc were translated to the Jura 
 when the intermediate country was under water:' Paper read to GeoL Soc. 
 London, May 30, 1849. 
 
152 NEWER PLIOCENE STRATA. [Cn. XIII 
 
 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 accu- 
 mulation 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 forma- 
 tions, 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 freshwater 
 deposits, as frequently happened in Auvergne (see above, p. 80), keeping 
 them free from intermixture with strata subsequently 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 when there have been 
 oscillations in the levels of the land, accompanied 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 sedimentary 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 classifica- 
 tion of these Pleistocene formations is involved. 
 
 At several points in the valleyof the Thames, remnants of ancient 
 fluviatile deposits occur, which may differ considerably in age, although 
 the imbedded land and freshwater shells in each are of recent species. 
 At Brentford, for example, the bones of the Siberian Mammoth, or 
 

 CH. XIII.] DEPOSITS IN VALLEY OF THAMES. 153 
 
 Elephas primigenius, and the Rhinoceros tichorhinus^looth of them quad- 
 rupeds of which the flesh and hair have been found preserved in the 
 frozen soil of Siberia, occur abundantly, with the bones of an hippopot- 
 amus, aurochs, short-horned ox, red deer, reindeer, 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 reindeer 
 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 equa- 
 torial 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 pre- 
 ceded 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 Brentford, although 
 the associated land and freshwater shells are nearly all, if not all, identi- 
 cal with species now living. Three of the shells, however, are no longer 
 inhabitants of Great Britain ; namely, Paludina marginata (fig. 11*7, p. 
 133), now living in France ; Unio littoralis (fig. 29, p. 28), now inhab- 
 iting the Loire; and Cyrena 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 men- 
 tioned, 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 mam- 
 malia is also found the Hippopotamus major, and what is most remark- 
 able 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 Wood- 
 ward, in the course of thirteen years, together with the oysters, above 
 
 * Morris, Geol. Soc. Proceed. 1849. 
 
164: FLTJVIO-MARINE NORWICH CRAG. [Cn. XIII 
 
 2000 mammoths' grinders.* Another portion of the same continuous 
 stratum has yielded at Bacton, Cromer, and other places on the coast, 
 the bones of a gigantic beaver (Trogontherium 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 mam- 
 miferous 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 contigu- 
 ous 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 supposed 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 Yare, 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 thickness, 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 Tel- 
 Una 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 
 
 * Woodward's Geology of Norfolk. f Zool. of Beagle, part 1, pp. 9, 111. 
 
OH. XIJL] NORWICH CRAG PLEISTOCENE. 
 
 Fig. 125. Fig. 126. 
 
 155 
 
 Fig. 127. 
 
 Nvctda CobMdia. 
 
 Tettina obliqua. 
 
 Natica helic&ides, 
 Johnston. 
 
 arvernensis* (see fig. 135, p. 165), 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 
 at Felixstow, and had hitherto been regarded as characteristic of forma- 
 tions 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. 167). I have seen the 
 tusk of an elephant from Bramerton near Norwich, to which many 
 serpulse 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 examined 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. 
 
 Owen, Brit. Foss. Mamm. 271. Mastodon longirostris, Kaup, see ibid. 
 
156 NEWER PLIOCENE STRATA. [On. XIII. 
 
 Newer Pliocene Strata of Sicily. In no part of Europe are the 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, arid near its centre, at Cas- 
 trogiovanni, they reach an elevation of 3000 feet. They consist princi- 
 pally of two divisions, the upper calcareous, 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. Ot 
 the remainder, which still live, five species are no longer inhabitants of 
 the Mediterranean. "When I visited Sicily in 1828 I estimated the pro- 
 portion of living species as somewhat greater, partly because I con- 
 founded with the tertiary formation 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 pas- 
 sage 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 generalization, several of the 
 places cited by him in confirmation having as yet furnished no more 
 than twenty or thirty species of testacea. The Sicilian 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 tex- 
 ture, is naturally surprised to behold formations of the same age so solid 
 and stony, of such thickness, and attaining so great an elevation above 
 the level of the sea. 
 
 The upper or calcareous member of this group in Sicily consists in 
 some places of a yellowish-white stone, like the calcaire grossier of Paris, 
 in others, of a rock nearly as compact as marble. Its aggregate thick- 
 ness amounts sometimes to 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 color, to others which are mere casts. 
 
 The limestone passes downwards into a sandstone and conglomerate, 
 below which is clay and blue marl, like that of the Subappenine 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, volcanoes burst out beneath the waters, like that 
 of Graham Island, in 1831, and these explosions recurred again and again 
 at distant intervals of time. Volcanic ashes and sand were showered 
 
CH. XIII.] 
 
 OF SICILY. 
 
 157 
 
 down and spread by the waves and currents so as to form strata of tuff, 
 which are found intercalated between beds of limestone and clay contain- 
 ing 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 Lentini, 
 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 tran- 
 quil 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 peb- 
 bles 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 thick- 
 ness rests upon a current of basaltic lava. The oysters are perfectly iden- 
 tifiable with our common eatable species. Upon the oyster bed, again, 
 is superimposed 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 corak stand erect as they grew ; 
 
 Fig. 128. 
 
 Caryophyllia ccespitosa, Lam. (Cladocora stellaria, Milne Edw. and Haime.) 
 
 a. Stem with young stem growing from its side. 
 
 a*. Young stem of same twice magnified. 
 
 &. 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. 
 a. 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. 
 
158 NEWER PLIOCENE STEATA OF SICILY. [On. X1IL 
 
 and, after being traced for hundreds of yards, are again found at a cor- 
 responding height on the opposite side of the valley. 
 
 The corals are usually branched, but not by the division of the animals 
 as some have supposed, but by the attachment of young individuals to 
 the sides of the older ones ; and we must understand this mode of in- 
 crease, 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 gen- 
 erations.* 
 
 Among the other fossil shells met with in these Sicilian strata, which 
 still continue to abound in the Mediterranean, no shell is more conspic- 
 uous, from its size and frequent occurrence, than the great scallop, Pecten 
 jacobceus (see fig. 129), now so common in the neighboring 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 jacolceus ; 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 deposited 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, conglomer- 
 ates, and sheets of lava ; and we must afterwards contemplate the time 
 
 * I am indebted to Mr. Lonsdale for the details above given respecting the 
 structure of this coral. 
 
CH. XIII] CAVE BRECCIAS. 159 
 
 required for .the gradual upheaval of the rocks, and the excavation of the 
 valleys. The historical period seems scarcely to form an appreciable unit 
 in this computation, for we find ancient Greek temples, like those of 
 Girgenti (Agrigentum), built of the modern limestone of which we are 
 speaking, and resting on a hill composed of the same ; the site having 
 remained to all appearance unaltered since the Greeks first colonized 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 zoophytes. 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 pre- 
 cisely 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 attributes 
 and migratory habits of animals and plants to the changes which are un- 
 ceasingly in progress in the physical geography of the globe. It is clear 
 that the duration of species is so great, that they are destined 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 spaces. 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 manner, 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 Ciro, near Palermo (p. To), that upon 
 
160 
 
 KIRKDALE CAVE. 
 
 [On. XIII 
 
 a bed of sand filled with sea-shells, almost all of recent species, rests a 
 breccia (6, fig. 93), 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 incumbent 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.) 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 per- 
 ceive that all the quadrupeds of which the remains are found in the sta- 
 lactite of these caverns, being of later origin than the rocks, must be re- 
 ferable 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. 180. 
 
 & 6 Deposits in caves f COQ t a i n i n g 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 a 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 (Hyaena spelced) is extinct, and was 
 larger than the fierce Hycena crocuta of South Africa, which it most re- 
 sembled. Dr. Buckland, after carefully examining 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 hyaena, 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 appear- 
 ance 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 supposed that portions of herbivorous quadrupeds have been dragged 
 into caverns by beasts of prey, and have served as their food, an opinion 
 quite consistent with the known habits of the living hyaena. 
 
 No less than thirty-seven species of mammalia are enumerated by Pro- 
 fessor Owen as having been discovered in the caves of the British islands, 
 of which eighteen appear to be extinct, while the others still survive 
 
CiLXIIL] AUSTRALIAN CAVERNS. 161 
 
 in Europe. They were not washed to the spots where the fossils now oc- 
 cur by a great flood ; but lived and died, one generation after another, in 
 the places where they lie buried. Among other arguments in favor of this 
 conclusion may be mentioned the great numbers of the shed antlers of deer 
 discovered in caves and in freshwater 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 alluvial 
 matter and fragments of rock detached by frost, forming a mass which 
 may be united into a bony breccia by stalagmitic infiltrations. Fre- 
 quently we discover a long suite of caverns connected by narrow and 
 irregular galleries, which hold a tortuous course through the interior of 
 mountains, and seem to have served as the subterranean channels of 
 springs and engulfed rivers. Many streams in the Morea are now car- 
 rying bones, pebbles, and mud into underground passages of this kind. 
 I 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 engulfed 
 streams may communicate with the surface, 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 conditions, and in their last state may have remained 
 open to the day for several tertiary periods. It is nevertheless re- 
 markable, that on the continent of Europe, as in England, the fossil 
 remains of mammalia 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 re- 
 cently 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 dis- 
 solved by rain. The rain-water, thus impregnated, permeates the porous 
 limestone, dissolves a portion of it, and afterwards, when the excess of 
 carbonic acid evaporates in the caverns, parts with the calcareous matter, 
 and forms stalactite. Such facts seem to imply that the date of the emer- 
 gence 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 stalactite deposit. 
 
 Australian cave-breccias. Ossiferous breccias are not confined to Eu- 
 rope, but occur in all parts of the globe ; and those lately discovered in 
 fissures and caverns in Australia correspond closely in character with 
 what has been called the bony breccia of the Mediterranean, in which the 
 
 * Oweu, Brit. Foss. Mara. xxvi. and Buckland, Rel. Dil. 19, 24. 
 11 
 
162 
 
 FOSSILS IN AUSTKALIAN CAVES. 
 
 [On. XIII 
 
 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 JETypsiprymnus, 
 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 the 
 largest living ones of the same genera now known in Australia. The 
 annexed figure of the right side of a lower jaw of a kangaroo (Macro- 
 
 Fig. 131 
 
 Macropus atlas, Owen. 
 a. Permanent false molar, in the alveolus. 
 
 pus atlas, Owen) will at once be seen to exceed in magnitude the cor- 
 responding part of the largest living kangaroo, which is represented in 
 
 Fig. 132. 
 
 Lowest jaw of largest living species of kangaroo. 
 (Macropua major.) 
 
EXTIXCT FOSSIL MAMMALIA. 163 
 
 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 
 Fig. 133. teeth. In fig. 133, a front tooth of the same species of 
 kangaroo, is represented. 
 
 Whether the breccias, above alluded to, of the Wellington 
 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 dis- 
 trict, 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 quadrupeds 
 of Australia belong to the marsupial family, or, in other 
 words, that they are referable to the same peculiar type of 
 organization which now distinguishes the Australian mam- 
 malia from those of other parts of the globe. This fact is 
 cropus. one O f manv pointing to a general law deducible from the 
 fossil vertebrate and invertebrate animals of the eras immediately ante- 
 cedent to the human, namely, that the present geographical distribution 
 of organic forms dates back to a period anterior to the creation of ex- 
 isting 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 Europseo- 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 Me- 
 gatherium, Megalonyx, Glyptodon, Mylodon, Toxodon, Macrauchenia, 
 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 rela- 
 tion to deposits of marine shells, agreeing with those now inhabiting the 
 Atlantic; and when in Georgia in 1845,1 ascertained that the Mega- 
 therium, Mylodon, Harlanus americanus (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 
 neighboring sea. 
 
 There are indeed some cosmopolite genera, such as the Mastodon (a 
 genus of the elephant family), and the horse, which were simultaneously 
 represented by different fossil species in Europe, North America, and 
 
164 EXTINCT FOSSIL MAMMALIA. [Cn. XIII 
 
 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 pres- 
 ent 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 disappearance of the 
 ancient fauna from so many extensive regions. Not a few of the species 
 had a wide range ' r the same Megatherium, for instance, extended from 
 Patagonia and the river Plata in South America, between latitudes 31 
 and 39 south, to corresponding latitudes 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 ele- 
 phant, 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 adapta- 
 tion of such quadrupeds to a variety of climates and geographical con- 
 ditions, 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 have all died out together, 
 while the land shells formerly their contemporaries still continue to exist 
 in the same countries. As we may feel assured that these minute quad- 
 rupeds eould 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 in- 
 definite ages, by those changes of circumstances in the organic and inor- 
 
 O ' / O O 
 
 ganic 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 Zealand, when first 
 examined by Europeans, was found to contain no indigenous land quad- 
 rupeds, no kangaroos, or opossums, like Australia ; but a wingless bird 
 abounded there, the smallest living representative of the ostrich family^ 
 called Kivi, by the natives (Apteryx). In 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 pro- 
 digious number of well-preserved specimens of gigantic birds of the stru- 
 thious order, called by Owen Dinornis and Palapteryx, which are en- 
 * See Principles of Geology, chaps, xli. to xliv. 
 
CH. XIII.] 
 
 TEETH OF FOSSIL QUADRUPEDS. 
 
 165 
 
 tombed in superficial deposits. These genera comprehended many spe- 
 cies, some of which were 4, some 7, others 9, and others 11 feet in 
 height ! It seems doubtful whether any contemporary mammalia shared 
 the land with this population 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 specimens, may be 
 useful in assisting the student to recognize the teeth of many genera most 
 frequently found fossil in the Newer Pliocene and Post-Pliocene periods : 
 
 Fig. 134. 
 
 Elepha* primigeniu* (or Mammoth) ; molar of upper jaw, right side ; one-third of nat size. 
 a. Grinding surface. &. Side view. 
 
 Fig. 135. 
 
 Mastodon arrernemia (Norwich Crag, Postwick, also found in Bed Crae, see p. 155); second 
 true molar, left side, upper jaw ; grinding surface, nat size. (See. p. 155.) 
 
166 
 
 TEETH OF FOSSIL MAMMALIA. 
 Fig. 136. Fig. 137. 
 
 Khinoceros. 
 
 Rhinoceros leptorMmis ; fos- 
 sil from freshwater beds of 
 Grays, Essex (see p. 153); 
 penultimate molar, lower 
 jaw, left side ; two-thirds of 
 Qat. size. 
 
 Hippopotamus. 
 
 Hippopotamus Penttandi, 
 H. v. Meyer; from cave 
 near Palermo (see p. 160) ; 
 molar tooth; two-thirds 
 of nat. size. 
 
 Pig. 
 
 8us scrofa, Lin. (common 
 pig) ; from shell-marl, 
 Forfarshire ; posterior 
 molar, lower jaw, nat. 
 size. 
 
 Fie. 139. 
 
 Fig. 140. 
 
 Horse. 
 
 Equus cabaUus, Lin. (common horse) ; 
 from the shell-marl, Forfarshire ; 
 second molar, lower jaw. 
 
 a. Grinding surface, two-thirds nat. size. 
 
 b. Side view of same, half nat. size. 
 
 Tapir. 
 
 Tapims America-tins 
 recent ; third mola 
 upper jaw; nat. size. 
 
 Fig. 141. 
 
 Fig. 142. 
 
 a. &. Beer. 
 
 Elk (Cervus alces, Lin.); re- 
 cent; molar of upper jaw. 
 
 a. Grinding surface. 
 I. Side view; two-thirds of 
 nat. size. 
 
 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. 
 
CH. XIV.] OLDER PLIOCENE FORMATIONS. 
 
 Fig. 143. Fig. 144. 
 
 167 
 
 Bear, 
 a. Canine tooth or tusk of bear ( Urrns 
 
 spelceus) ; from cave near Liege. 
 &. Molar of left side, upper jaw ; one 
 
 third of nat size. 
 
 Fig. 145. 
 
 Tiger. 
 
 c. Canine tooth of tiger (Fdis tigrte) ; 
 
 recent. 
 
 d. Outside view of posterior molar 
 
 lower jaw ; one-third of nat. size. 
 
 Fig. 146. 
 
 UyoRna spelcea: second molar, left 
 side, lower jaw ; nat size. Cave 
 ofKirkdale. (See p. 160.) 
 
 Teeth of a new species of Arvicola (field mouse) ; from the 
 
 Norwich Crag. (See p. 155.) 
 a. Grinding surface. &. Side view of same. 
 
 c. Nat size of a and &. 
 
 Fig. 147. 
 
 a. Fourth molar, right side, lower jaw. Megatherium; Georgia, 
 U. S. ; one-third nat size. 
 
 <L 
 
 Crown of same. 
 
 CHAPTER XIV. 
 
 OLDER PLIOCENE AND MIOCENE FORMATIONS. 
 
 Strata of Suffolk termed Red and Coralline Crag Fossils, and proportion of re- 
 cent 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 im. 
 plied by the testacea Proportion of recent species of shells Faluns more an- 
 cient than the Suffolk Crag Miocene strata of Bourdeaux of the Bolderberg 
 in Belgium of ISorth Germany Vienna Basin Piedmont Molasse of Swit- 
 zerland Leaf-beds of Mull in Scotland Older Pliocene and Miocene forma- 
 tions in the United States Sew^lik 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 Suffolk, 
 
168 OLDER PLIOCENE FORMATIONS. [On. XIV 
 
 where, like the Norwich beds already described, they are called " Crag, 7 ' 
 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 ac- 
 companying diagram (fig. 148). 
 
 Fig. 148. 
 Crag. London Clay. Chalk. 
 
 These deposits, according to Professor E. Forbes, appear by their im- 
 bedded 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 comminuted. In many 
 places fossils washed out of older tertiary strata, especially the London 
 Clay, are met with. The lower or coralline Crag is of very limited ex- 
 tent, 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 Oxford, 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 neighborhood, 
 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 
 color of its sands and fossils, the Coralline by its white color. Both for- 
 mations are of moderate thickness ; the Red Crag rarely exceeding 40, 
 and the Coralline seldom amounting to 20 feet. But their importance 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 
 
 * 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 popu- 
 larly included in the corals, but now classed by naturalists as mollusca. The 
 term Polyzoum, synonymous with Bryozoum, was, it seems, proposed in 1830, or 
 the year before, by Mr. J. V. Thompson, but is less generally adopted. The ani- 
 mals of the Zoantharia of Milne Edwards and Haime, or the true corals, have 
 only one opening to the stomach. 
 
CH. XIV.] SUFFOLK CRAG. 169 
 
 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 cor- 
 als of the deposits in Suffolk, we are indebted to the labors 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 
 conchologists, I came to the opinion that the extinct species predominated 
 very decidedly in number over the living. Recent investigations, how- 
 ever, have thrown much new light on the conchology of the Arctic, 
 Scandinavian, British, and Mediterranean Seas. Many of the species for- 
 merly 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 ex- 
 plored. 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 suspected, and thus have been identified. Consequently, 
 the Crag fauna has been found to approach much more nearly to the re- 
 cent fauna of the Northern, British, and Mediterranean Seas than had 
 been imagined. The analogy of the whole group of testacea to the Eu- 
 ropean type is very marked, whether we refer to the large development 
 of certain genera in number of species or to their size, or to the sup- 
 pression or feeble representation of others. The indication also afforded 
 by the entire fauna of a climate not much warmer than that now pre- 
 vailing in corresponding latitudes, prepares us to beh'eve 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 for- 
 mation a was thrown down upon it. At D there is not only a distinct 
 
 Fig. 149. 
 Button. 
 
 Section near Ipswich, in Suffolk. 
 a. Bed Crag. 6. Coralline Crag. c. London Clay. 
 
 cliff, 8 or 10 feet high, of Coralline Crag, running in a direction K E. and 
 S. W., against which the red crag abuts with its horizontal layers ; but 
 
 * See Monograph on the Crag Mollusca. Searles Wood, Paleont. Soc. 1848. 
 
170 OLDER PLIOCENE FORMATIONS. [On. XIY 
 
 this cliff occasionally overhangs. The rock composing it is drilled every 
 where by Pholades, the holes which they perforated having been after 
 wards filled 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 incoherent ma- 
 terials, without many of the fossils of the inferior beds becoming mixed up 
 with the overlying crag, so that considerable difficulty must be occasion- 
 ally 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 struc- 
 ture 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 sub- 
 sequent concretionary rearrangement of particles, or to mere lines of color, 
 is proved by each bed being made up of flat pieces of shell which lie par- 
 allel 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 Bucdnum (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. 
 
 Fusm contrarius. Murex atoeolatus. Cyprceo. coccinelloides. 
 
 Fig. 150 half nat. size ; the others nat size. 
 
 Among the bones and teeth of fishes are those of large sharks ( Carcha- 
 rodon), 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, 
 
CH. XIV.] FOSSILS OF THE SUFFOLK CEAG. 1T1 
 
 and of which a fragment (the Hempstead beds of Forbes) escaped denu- 
 dation in England. 
 
 The distinctness of the fossils of the Coralline from those of the 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 Eed 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, Bucdnum, 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), which is one 
 
 Fig. 154. 
 
 
 
 Fascicularia aurantium, Milne Edwards. Family, Tubuliporidce, of same author. 
 Bryozoan of extinct genus, from the inferior or Coralline Crag, Suffolk. 
 
 a. Exterior. 5. 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. 
 
 of several species having a globular form. The^reat 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 Glycinieris, Cyprina, and Astarte. Of the genus last mentioned 
 (see fig. 155) there are about fourteen species, many of them being rich 
 in individuals ; and there is an absence of genera peculiar to hot climates, 
 such as Conus, Oliva, Mitra, Fasciolaria, Crassatella, and others. The 
 cowries (Cyprcea, fig. 153), also, are small, and belong to a section (Trivia) 
 now inhabiting the colder regions. A large volute, called Valuta Lam- 
 berti (fig. 156), may seem an exception ; but it differs in form from the 
 
172 
 
 OLDER PLIOCENE FORMATIONS. 
 Fig. 155. 
 
 [Ctt XIV. 
 
 Astarte (Orassina, 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. 
 
 volutes of the torrid zone, and may, like the living Valuta Magellanica, 
 have been fitted for an extra-tropical climate. 
 
 Fig. 156. 
 
 Fig. 157. 
 
 Fig. 158. 
 
 Valuta, Lambertl, young 
 Individ., Cor. and Kec 
 Crag. 
 
 Pyrula reticulata, Lam. ; 
 Coralline Crag, Eam- 
 
 Temnechinus excavatus, 
 Forbes; Temnopleurus 
 excavatus, Wood ; Cor. 
 Crag, Ramsholt 
 
 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 an<i 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 com- 
 parison 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 estab- 
 lished in the temperate zone, retreated southwards to avoid an uncon- 
 genial climate. The Professor has given a list of fifty shells which in- 
 habited the British seas while the Coralline and Red Crag were forming; 
 
Cn. XIV.] SUBAPENNINE STEATA. 173 
 
 and which, though now living in our seas, are all wanting in the Pleisto- 
 cene 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 Sicily, 
 Southern Italy, and the Grecian Archipelago, where they may have en- 
 joyed, 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, according to Prof. 
 Owen, are the remains of true whales of the family Balcenidce (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 destrucl'on 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 testacea 
 
 Fig. 159. Fig. 160. 
 
 Tympanic bone of Ealasna emarginata, Lingula Dumortieri, Nyst ; 
 
 Owen ; Bed Crag, Felixstow. Antwerp Crag. 
 
 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 corresponding 
 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 composed 
 chiefly of secondary rocks, forming a chain which branches off from the 
 Ligurian Alps and passes down the middle of the Italian peninsula. At 
 
 * E. Forbes, Mem. GeoL Survey, Gt. Brit. vol. i. 386. 
 
 j- Lyell on Belgian Tertiaries, Quart Journ. Geol. Soc. 1852, p. 882. 
 
174 SUBAPENNINE STRATA. [Off. XIV. 
 
 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. 110), was the first Italian 
 geologist who described this newer group in detail, giving it the name of 
 the Subapennines ; and he 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, be- 
 long nevertheless, in part, both to older and newer members of the ter- 
 tiary 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 ter- 
 ritory approach more nearly to the recent fauna of the Mediterranean, and 
 may be Newer Pliocene. 
 
 The grayish-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 occasionally formed 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 color, 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 con- 
 glomerate, 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 immediately on the 
 Apennine limestone, without the intervention of any blue marl. Alterna- 
 tions are there seen of beds containing fluviatile shells, with others filled 
 exclusively with marine species ; and I observed 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 
 
CH.XIV.] MIOCENE FOKMATIOJSTS. 175 
 
 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 de- 
 posited. 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 afterwards be spread, in proportion as 
 rivers pushed their deltas farther outwards. In some large tracts of yel- 
 low sand it is impossible to detect a single fossil, while in other places 
 they occur in profusion. Occasionally the shells are silicified, as at San 
 Vitale, near Parma, from whence I saw two individuals of recent species, 
 one freshwater and the other marine (Lymnea palustris, and Cytherea 
 concentrica, Lam.), both perfectly converted into flint. 
 
 Rome. The seven hills of Home are composed \ artly of marine ter- 
 tiary 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 terrestrial 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 dis- 
 cover the extremely recent date of a geological event which preceded an 
 historical era so remote as the building of Rome. 
 
 Aralo- Caspian formations. This name has been given by Sir R. Mur- 
 chison 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, Azoff, and Aral Seas, and parts of the northern 
 and western coasts of the Black Sea. The fossil shells are partly fresh- 
 water, as Paludina, Neritina, <fec., and partly marine, of the family Car- 
 dizcice and Mytili. The species are identical, 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 occasionally 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 de- 
 scending order are those called by many geologists " Middle Tertiary," 
 
 * Geol. of Russia, p. 279, <fcc. 
 
176 FALUNS OF TOURAINE. [Cn. XIV. 
 
 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 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 neighborhood 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. De- 
 posits of the same age also appear under new mineral conditions near the 
 towns of Dinan and Rennes, in Brittany. I have visited all the locali- 
 ties above enumerated, and found the beds on the Loire to consist princi- 
 pally 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 successively upon gneiss, clayslate, various secondary for- 
 mations, including the chalk ; and, lastly, upon the upper freshwater 
 limestone of the Parisian tertiary series, which, as before mentioned 
 (p. Ill), stretches continuously from the basin of the Seine to that of 
 the Loire. 
 
 At some points, as at Louans, south of Tours, the shells are stained of 
 a ferruginous color, not unlike that of the Red Crag of Suffolk. The 
 species are, for the most part, marine, but Fig. iei. 
 
 a few of them belong to land and fluviatile 
 genera, Among the former, Helix turo- 
 nensis (fig. 45, p. 30) is the most abun- 
 dant. Remains of terrestrial quadrupeds 
 are here and there intermixed, belonging 
 to the genera Deinotherium (fig. 161), 
 Mastodon, Rhinoceros, Hippopotamus, 
 Chseropotamus, Dichobune, Deer, and 
 others, and these are accompanied by 
 cetacea, such as the Lamantine, Morse, 
 Sea-Calf, and Dolphin, all of extinct 
 
 species. Deinotherium giganteum, Kaup. 
 
 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 mol- 
 
CH. XIV.] COMPARISON OF THE CRAG AJSTD FALUNS. 177 
 
 luscous fauna of the " faluns" is on the whole much more littoral than 
 that of the Bed 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, sev- 
 eral species of Oliva, Ancillaria, Mitra, Terebra, Pyrula, Fasciolaria, 
 and Conus. Of the cones there are no less than eight species, some very 
 large, whereas the only European cone is of diminutive size. The genus 
 Nerita, and many others, are also represented 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 northwest 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 pos- 
 session, 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 ad- 
 verted to, amounts to forty-three, as determined by Mr. Lonsdale, of which 
 seven (one of them a zoantharian) agree specifically with those of the Suf- 
 folk 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, Lunu- 
 lites, 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 for- 
 merly endeavored to reconcile this marked difference in species with the 
 supposed coexistence of the two faunas, by imagining them to have sever- 
 ally 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 Eed Sea and the Medi- 
 terranean. But I now abandon that idea for several reasons ; among 
 others, because I succeeded in 1841 in tracing the Crag fauna southwards 
 in Normandy to within seventy miles of the Falunian type, near Dinan, 
 
 12 
 
178 SHELLS IN MIOCENE STRATA. [On. 
 
 yet found that both assemblages of fossils retained their distinctive char 
 acters, showing no signs of any blending of species or transition of cli- 
 mate. 
 
 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 proportion of fifty-seven 
 per cent., a fourfold greater specific resemblance than between the seas of 
 the crag and the faluns, notwithstanding the greater geographical dis- 
 tance between England and the Mediterranean 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, con- 
 sist in the predominance of fossil shells in the British strata identifiable 
 with species, not only still living, but which are now inhabitants of neigh- 
 boring 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 ar.e now inhabitants of the 
 Mediterranean, 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. 
 
 Bourdeaux. 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 Bourdeaux, 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 Brus- 
 sels, 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 genera Oliva, Conus, 
 Ancillaria, Pleurotoma, and Cancellaria in abun- 
 dance. 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 Bourdeaux species. f 
 
 North Germany. We learn from the able trea- 
 tise published by M. Beyrich, in 1853, that the 
 fossil fauna above alluded to, which is so meagerly 
 exhibited in the Bolderberg, is rich in species in a > fro ^ view ; &, back view. 
 other localities in North Germany, as in Mecklenburg, Liineburg, the 
 
 * See a Memoir by V. Raulin, 1848 : Bourdeaux. 
 
 f Lyell on Belgian Tertiaries, Quart. Geol. Journ. 1852, p. 295. Nyst's figure 
 seems to be copied from that given by Basterot of the Bourdeaux fossil. 
 J Die Conchylien des Norddeutschen Tertiargebirge : Berlin, 1853. 
 
CH. XIV.] SHELLS IN MIOCENE STRATA. 179 
 
 Island Sylt, and at Bersenbrtick north of Osnabriick, in Westphalia, 
 where it was first discovered by F. Komer. 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. 
 
 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 characteristic, and is supposed 
 
 Fig. 163. 
 
 Ampkistegina ffatierina, D'Orb. Vienna, miocene strata. 
 
 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 Switzerland, 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," sometimes attaining the truly wonderful 
 thickness of 6000 and 8000 feet, as in the Riga 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 headland of 
 Ardtun on the west coast of Mull, in the Hebrides, several bands of ter- 
 tiary strata containing leaves of dicotyledonous plants were discovered *in 
 1851 by the Duke of Argyle.f From his description it appears that 
 there are three leaf-beds, varying in thickness from 1 J to 2j 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 ; 
 
 * See Sig. Giov. Micnelotti's works. \ Quart GeoL Journ. 1851, p. 89. 
 
180 PLIOCENE AND MIOCENE FORMATIONS- [On. XIV 
 
 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. 
 
 It is supposed by the Duke of Argyle that this formation was accumu- 
 lated in a shallow lake or marsh in the neighborhood 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 cre- 
 taceous fossils were detected by the Duke in the principal mass of vol- 
 canic 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 Pro- 
 fessor E. Forbes, " is more mid-European than that of the English Eocene 
 Flora. They also resemble some of the Miocene plants of Croatia de- 
 scribed 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 un- 
 certainty in determining whether these beds are Upper Eocene or Mio- 
 cene, which we experience when we endeavor to fix the age of many con- 
 tinental Brown-Coal formations, those of Croatia not excepted. 
 
 These interesting discoveries in Mull naturally raise the question, 
 whether the basalt of Antrim in Ireland, and of the celebrated Giant's 
 Causeway, may not be of the same age. For in Antrim the basalt over- 
 lies 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 preserved.f The general dearth of strata in the British 
 Isles, intermediate in age between the formation of the Eocene and Plio- 
 cene periods, may arise, says Professor Forbes, from the extent of dry land 
 which prevailed in the last interval of time alluded to. If land predomi- 
 nated, the only monuments we are likly ever to find of Miocene 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 flanks of 
 Mont Dor, in Auvergne, I have seen leaf-beds among the ancient volcanic 
 tuffs which I have always 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. Be- 
 tween 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 elevation of this plain 
 
 * Quart. Geol. Journ. 185T, p. 90. f Duke of Argyle, ibid. p. 101. 
 
CH. XIV.] IX UNITED STATES, AND IN INDIA. 181 
 
 bordering the Atlantic does not exceed 100 feet, although it is sometimes 
 several hundred feet high. It* width in the middle and southern states 
 is very commonly from 100 to 150 miles. It consists, in the south, as in 
 Georgia, Alabama, and South Carolina, almost exclusively of Eocene de- 
 posits ; but in North Carolina, Maryland, Virginia, Delaware, more 
 modern strata predominate, which, after examining them in 1842, 1 sup- 
 posed 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 European 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 neighboring Atlantic, the number may hereafter 
 be augmented, when the recent fauna of that ocean is better ktiown. 
 In different localities, also, the proportion of recent species varied con- 
 siderably. 
 
 On the banks of the James River, 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 Vir- 
 ginian 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. bipartita) ; the other shells 
 also, of the genera Natka, Fissurella, Artemis, Lucina, Chama, Pectun- 
 culus, 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 
 
 Fig . 165 . 
 
 Fulgur canaliculatus. Maryland. Fusus quadricoslatus, Say. Maryland. 
 
 Touraine ; but it is an important characteristic of the American group, 
 that it not only contains many peculiar extinct forms, such as Fusus 
 
 * Proceed, of the Geol. Soc. vol. iv. part 3, 1845, p. 547. 
 
182 PLIOCENE AND MIOCENE FORMATIONS, ETC. [Cii. XIV 
 
 quadricostatus, Say (see fig. 165), and Venus tridacnoides, abundant in 
 these same formations, but also some shells which, like Fulgur carica 01 
 Say and F. canaliculatus (see fig. 164), Calyptrcea costata, Venus merce- 
 naria, 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 pres- 
 ent 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 exceeding that of the 
 Mediterranean, and the shells would lead to sim- 
 ilar conclusions. Those occurring on the James 
 River are in the 37th degree of N. latitude, 
 while the French faluns are in the 47th : yet 
 
 , <!* />M IT i Astrangia linecita, Lonsdale. 
 
 the lorms or the American lossils would scarcely gyn. Anthophyiium Uneatum. 
 imply so warm a climate as must have prevailed Williams ^ r 's h . Virginia. 
 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-Hima- 
 layan or Sewalik Hills, described by Dr. Falconer and Captain Cautley, 
 belong probably to some part of the Miocene period, although it is diffi- 
 cult to decide this question until the accompanying freshwater and land- 
 shells have been more carefully determined and compared with fossils of 
 other tertiary deposits. The strata are certainly newer than the num. 
 mulitic rocks of India, and, like the faluns of Touraine, they contain the 
 genera Deinotheri:im 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 Anoplotherium (A. posterogenium) 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 referable to existing genera, whereas almost every Eocene 
 genus is extinct. Moreover, the sub-Himalayan fauna exhibits a great 
 development 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 rhi- 
 noceros, and provided with a large upper lip, if not a short proboscis, and 
 
CH. XV.] UPPER EOCEXE FORMATIONS. 183 
 
 having two pair of horns resembling those of antelopes. The number of 
 species of the genus Antelope is also remarkable. In the same fauna 
 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 for- 
 mations 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 Bourdeaux, Aix-en-Provence, Malta, <kc. 
 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, how- 
 ever, been recently discovered in the Isle of Wight certain fluvio-marine 
 deposits, which many continental geologists would call " Lower Miocene," 
 the " faluns" being termed by them " Upper Miocene." A few prelimi- 
 nary remarks on this difference of nomenclature, bearing as it does on 
 questions involving the first principles of classification, will be necessarj 
 before I treat of the Upper Eocene formations. 
 
 The marine strata, which in the north of France come next in chrono- 
 logical order to the " faluns," or which immediately precede them in age, 
 are the sands and sandstones, called the " Ores de Fontainebleau," 01 
 "sables marins superieurs." (See General Table, p. 104.) They consti- 
 tute the uppermost beds of the Paris basin, and are overlaid by a fresh- 
 water limestone called " Calcaire de la Beauce." The upper marine sands 
 ontain no fossil shells common to the faluns, or extremely 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 Ores de Fontainebleau 
 and the faluns to draw a line of separation between Eocene and Miocene. 
 
184: KEMARKS ON CLASSIFICATION. [Cn. XV 
 
 In support of this classification I pointed out the fact that the " uppei 
 marine sands," or Gres 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, 
 rtiid not more than 100 miles from Savigne, near Tours, two localities 
 where fhefalunian 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 differ- 
 ence in the age of the deposits. It marks the influence of Time, and 
 not of Space. 
 
 Another reason which induced me to class the Gres de 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 coloring of the Government Map of France, for 
 they comprehended in their Miocene group, not only the faluns of Tou- 
 raine, but also the freshwater " calcaire de la Beauce," and the marine 
 sands and sandstone (Gres de Fontainebleau), i. e. all the tertiary de- 
 posits which lie above the gypseous series of Montmartre, 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 ter- 
 tiary" 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 distin- 
 guished specifically from shells of the Calcaire Grossier, although he 
 regarded them as characteristic of the same fauna. The railway cut- 
 tings 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 described 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 un- 
 doubted representatives of the Calcaire Grossier 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. 
 
CH. XV.] UPPER EOCENE FORMATIONS. 185 
 
 In 1851, I examined with care the Belgian formations at Rupelmonde 
 and Boom, near Antwerp, and in the Limburg, near Maestricht, 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 consideration. 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 exam- 
 ple, 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 exam- 
 ined 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 
 conformable 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 Limburg 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 forma- 
 tion) 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 Ger- 
 many, M. Beyrich, before cited,f and Dr. SandbergerJ contend that all 
 strata, parallel in age with the Limburg, should be termed Lower- Mio- 
 cene. M. Beyrich affirms that if the strata of the Bolderberg in Bel- 
 gium, and numerous deposits of contemporaneous date of Northern 
 Germany already enumerated (p. 178), 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 
 
 * Quart. Geol. Journ. 1852, vol. riii. p. 322. 
 
 f Die Conchylien des Xorddeutsch. Tertiiirgeb. : Berlin, 1853. 
 
 t Uber das Mainzer Tertiarbeckens, &c. : Wiesbaden, 1853. 
 
186 SEPARATION OF EOCENE AND MIOCENE STRATA. [On. XV 
 
 Miocene. Dr. Sandberger divides the strata of the Mayence basin into 
 two sections, an older and a newer, the former confessedly the equiva- 
 lent of the Limburg (or Hempstead) beds, while in the upper he find., 
 some fossil remains, which appear to him to have a more modern char 
 acter. But when we separate from this higher division the sands c 
 Eppelsheim, containing bones of Deinotherium and Mastodon longirostrit 
 which are most probably of falunian age, the rest of his upper seriei 
 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, besides some teeth ol 
 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 
 ^or determining their true age, appear clearly to belong to a more mod- 
 ern fauna than that of the Mayence basin. If such a relationship could 
 be established between the two as to indicate a passage 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 ter- 
 tiary 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 oui, 
 of old ones, and a gradual change in the physical geography and cli- 
 mate of the earth, and not such a reiteration of sudden revolutions in the 
 animate and inanimate worlds, as was once insisted upon by many Eng- 
 lish 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 seventeen 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 for- 
 mations, 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 
 
Ca XV.] EOCENE AND MIOCENE STRATA. 187 
 
 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 Touraine. 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 paleonto- 
 logical 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 fossils of the groups alluded to resemble more 
 nearly the Eocene or the Falunian. I adhere at present to the nomen- 
 clature 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 " nummulitie" Eocene beds, but be- 
 cause of the aspect of the whole fauna, which seems to me to be Eocene 
 rather than Falunian. 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 Hamp- 
 shire, 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 disappeared more com- 
 pletely, it appears to me safer to include the Limburg and all contem- 
 poraneous 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 Bem- 
 bridge and Hempstead series, in the Isle of Wight, has been shown by 
 Professor Forbes to be an arbitrary one a purely conventional line, 
 if any thing, less marked than the line separating the Bembridge series 
 from the underlying St. Helen's group. (See Table, p. 209.) If re- 
 tained as more useful, it is, as before hinted, for the sake of confor- 
 mity with a system of classification adopted by many able geologists, 
 who selected it before the uninterrupted continuity of the Eocene series 
 
188 LIMBURG STRATA IN BELGIUM. [On. XV 
 
 from its nummulitic or central portions to its Upper or Limburg beds 
 was clearly made out. 
 
 LIMBUR& STRATA IN BELGIUM. 
 
 (Rupflian and Tongrian Systems of Dumont.) 
 
 The best type which we as yet possess of the Upper Eocene, as defined 
 in the foregoing observations, consists of the beds formerly known to col- 
 lectors 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 Maestricht, 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 of fish. 
 
 The following table will show the position of the Limburg beds. 
 
 MIOCENE. 
 A. Bolderberg beds, see p. 178, seen near Hasselt. 
 
 UPPER EOCENE. 
 
 B. 1. Nucula Loam of Kleyn Spawen, same ) Upper Limburg beds. Rupelian 
 age as clay of Rupelmonde and Boom. J of Duinont. 
 
 B. 2. Fluvio-marine beds of Bergh, Lethen, ) Middle Limburg beds. Upper 
 and other places near Kleyn Spawen. y Tongrian of Dumont. 
 
 B. 3. Green sand of Bergh, Neerepen, &c., ) Lower Limburg Beds. Lower 
 near Kleyn Spawen : Marine. y Tongrian of Dumont. 
 
 MIDDLE EOCENE. 
 
 C. Lacken and Brussels beds, with num- 
 mulites, &c. : Louvaiu and Brussels. 
 
 The uppermost of the three subdivisions (B. 1) into which the Limburg 
 series is separated in the abov 3 table, contains at Kleyn Spawen many of 
 the same fossils as the clay o: 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 abun- 
 
 Fig. 167. 
 
 Leda Deshayesiana. Nyst Syn. Nueula, Deshayesiana. 
 
CH. XV.] STEATA IX NORTH GER3IAXY. 189 
 
 dant ; a fossil unknown as yet in the English tertiary strata, but when 
 young much resembling Leda amygdaloides of the London clay proper 
 (see fig. 227, p. 218). Among other characteristic shells are Pecten 
 Hoeninghausii, 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 simulatus, Sow., Cancellaria evulsa, Brander, 
 Corbula pisum (fig. 170, p. 193), and Nautilus ziczac. They are accom- 
 panied by many teeth of sharks, as Lamna contortidens, Ag., Oxyrhina 
 riphodon, 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 Spawen, where the lower divisions 
 B. 2 and B. 3 are much better developed. B. 2 consists of several alter- 
 nations 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 semistriata (fig. 171, p. 
 193), Cerithium plicatum, Lam. (fig. 172, p. 193), Rissoa Cliastelii, 
 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 ventilabrum is very conspicuous. Spe- 
 cies 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 Nystii, Valuta saturalis, &c. 
 
 In none of the Belgian Upper Eocene strata, could I find any nummu- 
 lites ; and M. D'Archiac had previously observed that these foraminifera 
 characterize his " Lower Tertiary Series," as contrasted with the Middle, 
 anc tTould therefore serve as a good test of age between Eocene and Mio- 
 cene, 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 naturalist informs us that one nummu- 
 lite only has ever yet been seen to penetrate upwards into the middle 
 tertiary, viz., Nummulites intermedia, an Eocene species. It has been 
 found in the hill of the Superga near Turin,* in beds usually classed as 
 Miocene, but probably 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-gray color, and, like that of Rupelmonde, contains 
 septaria. Among other v shells, the Leda Deshayesiana before mentioned 
 (fig. 167) abounds, together with many species of Pleurotoma, Voluta, &c., 
 
 * Archiac, Monogr. pp. 79, 100. 
 
190 MAYENOE BASIN. [On. XV. 
 
 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 description 
 published by Dr. F. Sandberger of the Mayence tertiary area, which oc- 
 cupies a tract from five to twelve miles in breadth, extending for a great 
 distance along the left bank of the Rhine from Mayence to the neighbor- 
 hood of Manheim, and which is also found to the east, north, and south- 
 west of Frankfort. M. De Koninck, of Liege, first pointed out to me that 
 the purely marine portion of the deposit (the Lower group of Dr. Sand- 
 berger) 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. flandricum, De Koninck), Tornatella simulata, Rostellaria 
 Sowerbyi, Leda Deshayesiana (fig. 167, p. 188), Corbula pisum (fig. 1*70), 
 and Pectunculus terebratularis. 
 
 The marine beds are in some places covered with brackish-water 
 marls containing Cyrence in great numbers, among which Cyrena semis- 
 triata occurs, with Cerithium plicatum, Corbulomya triangula, Mytilus 
 Fanjasii, and other Limburg and Hempstead shells. Perna Soldani, a 
 shell of the upper Eocene or Merignac beds of the Bourdeaux basin, but 
 also a Vienna basin shell, is characteristic both of the marine and brackish 
 series. Two species of Anthracotherium, A. magnum, Cuv., and A. al- 
 saticum, 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 incrassata, Sow., a fossil 
 common to the Headon or Middle Eocene of England, are met with ; alsc 
 Neritina concava (fig. 194), a Middle Eocene shell, and Rhinoceros in- 
 cisivus, 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 others of the same genus. One of these, very 
 nearly resembling the recent Littorinella ulva, is found through- 
 out this basin. These shells are like grains of rice in size, and Fig% 16S * 
 are often in such quantity as to form entire beds of marl and 
 limestone, in stratified masses from fifteen to thirty feet in 
 thickness, just as in the Baltic modern accumulations 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. Sandberger believes. Among the Mammalia, 
 we find Hippotherium gracile, Acerotherium (or Rhinoceros) incisivum, 
 Paleomeryx, Chalicomys, &c. Lastly, the Eppelsheim sand overlies the 
 whole, containing Deinotherium giganteum, and some other true Miocene 
 
CH. XV.] 
 
 BROWN COAL OF GERMANY. 
 
 191 
 
 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 de- 
 posits 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 older than the Pliocene formations. 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 be- 
 long 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 contemporaneous marine or even fluvio marine beds were in progress 
 there. 
 
 The brown coal of Brandenburg, on the borders of the Baltic, under- 
 lies the Hermsdorf tile-clay already spoken of, and therefore belongs to 
 a period at least as old as the Upper Eocene. The brown coal of 
 Radoboj, 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 principal 
 brown coal formations, several species of 
 fan-palm or Flabellaria abound. This genus 
 also appears in the Middle Eocene or Bern- 
 bridge beds in the Isle of Wight, and in the 
 gypseous series of Montmartre ; but it is still 
 more largely represented in the Upper Eo- 
 cene series, accompanied by palms of the 
 genus Phoenicites. Various cones, and the 
 leaves and wood of coniferous trees, are also 
 met with at Radoboj. Species also of 
 Comptonia and Myrica, with various trees, 
 such as the plane or Platanus, are recog- 
 nized by their leaves, as also several of the Laurel tribe, especially one, 
 called Daphnogene cinnamomifolia (fig. 169) by Unger, who, together 
 
 Fig. 169. 
 
 Daphnogene cinnamomifolia, 
 Altsattel, in Bohemia. 
 
192 UPPER EOCENE STEATA OF ENGLAND. [On. XV. 
 
 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 the Mayence basin or in the Sieben- 
 gebirge, and in the neighborhood 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 out- 
 pourings, are certainly of much later date. 
 
 UPPER EOCENE STRATA OP ENGLAND. 
 
 Hempstead beds. Isle of Wight. Until veiy lately it was supposed 
 by English geologists that the newest tertiary strata of the Isle of Wight 
 corresponded in age with the gypseous series of Montrnartre near Paris ; 
 and this idea was confirmed by the fact that the same species of Palceo- 
 therium, Anoplotherium, and other extinct mammalia so characteristic of 
 the Parisian series, were also found at Binstead, near Hyde, in the north- 
 ern district of the island, forming part of the fluvio-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. 104, et seq.) rest immediately upon the Headon series ; 2dly, 
 the St. Helen's series is succeeded by the Bembridge beds before men- 
 tioned, the equivalent of the Montmartre gypsum ; and 3dly, 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 Wightf The following is the suc- 
 cession of strata there discovered, the details of which are important 
 for reasons explained in the preliminary remarks of this chapter (p. 
 187) : 
 
 * E. Forbes, Geol. Quart. Journ. 1853. 
 
 \ This hill must not be confounded with Hampstead Hill, near London, where 
 the Lower Eocene or London Clay is capped by Middle Eocene sands. 
 
CH. XV.] 
 
 UPPER EOCENE, ISLE OF WIGHT. 
 
 193 
 
 SUBDIVISIONS OF 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. 1 71, 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 
 
 Fig. 172. 
 
 Fig. 173. 
 
 Fig. 174 
 
 Fig. 175. 
 
 Cerithium plicatum, Cerithium elegans, Risoa Chastelii, Nyst, 
 Lam. Hempstead. Hempstead. Sp. Hempstead, Isle 
 
 Paludina lenta. 
 Hempstead Beds. 
 
 lent a, fig. 175, occurs a shell identified by some conchologists with a species 
 now living, P. unicolor ; also several species of Lymneus, Planorbis, and Unio. 
 
 8. 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., Me- 
 lanopsis, &c. The bottom bed is carbonaceous, and called the "Black band," 
 in which Jtissoa 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 Char a medicaginula, 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. 
 
 13 
 
194 UPPER EOCENE STRATA OF FRANCE. [On. XV 
 
 Between the Hempstead beds above described and those next below them, there 
 is no break, as before stated, p. 187. 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, Pain- 
 dina 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 beds Middle Eocene, for convenience sake, as 
 already explained (pp. 183, 187.) 
 
 UPPER EOCENE STRATA OF FRANCE. 
 
 (Lower Miocene of many French authors) 
 
 The Gres de Fontainebleau, or sandstone of the Forest of Fontainebleau, 
 has been frequently alluded to in the preceding pages, as corresponding 
 in age to the Limburg or Hempstead beds. It is associated in the sub- 
 urbs 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 in- 
 crassata 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 over- 
 spread the newest parts of great deltas. Beds of flint, continuous or in 
 nodules, accumulated in these lakes, and Charce, 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 sum- 
 mits 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 
 boundaiy of the marine Miocene faluns, fragments of the older freshwater 
 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 France. 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 mountain- 
 ous region, and have been each fed by one or more rivers and torrents. 
 
OH. XV.] UPPER EOCENE OF CENTRAL FRANCE. 195 
 
 Fig. 176. 
 
196 SUCCESSION OF CHANGES IN AUVEKGNE. [Cs. XT 
 
 The country where they occur is almost entirely composed of granite 
 and different varieties of granitic schist, with here and there a few 
 patches of secondary strata, much dislocated, 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 fresh- 
 water strata, and is sometimes seen to rest upon them, while a small part 
 has evidently been of contemporaneous origin. Of these igneous rocks 
 T 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 ter- 
 tiary 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 disappeared, lofty moun- 
 tains have been formed, by the reiterated emission of lava, preceded and 
 followed by showers of sand and scoriae, deep valleys have been sub- 
 sequently 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 completed. 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 cal- 
 careous rocks precipitated from the waters of mineral springs ; shells and 
 insects imbedded, together with the remains of the crocodile and tor- 
 toise, the eggs and bones of water birds, and the skeletons of quadru- 
 peds, 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 
 ',aken place after the disappearance of the upper Eocene fauna, and partly 
 in the Miocene epoch, the mastodon, rhinoceros, elephant, tapir, hippo- 
 potamus, 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 
 
OH. XV.] LACUSTRINE STRATA AUVERGNE. 197 
 
 flows of mud, such as accompany volcanic eruptions. Lastly, these quad- 
 rupeds became extinct, and gave place to Pliocene mammalia (see chap. 
 xxxii.V 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 ac- 
 complished by currents in the different lakes, or by rivers and floods ac- 
 companying repeated earthquakes, during which the levels of the district 
 have in some places been materially modified, and perhaps the whole up- 
 raised relatively to the surrounding parts of France. 
 
 Auvergne. The most northern of the freshwater groups is situated in 
 the valley-plain of the Allier, which lies within the department of the Puy 
 de Dome, being the tract which went formerly by the name of the Li- 
 magne 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, sandstone, calcareous marl, clay, and limestone, none of which ob- 
 serve a fixed and invariable order of superposition. The ancient borders 
 of the lake, wherein the freshwater strata were accumulated, may gen- 
 erally 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 in- 
 tervenes between them. The freshwater strata may sometimes be seen 
 to retain their horizontally 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 sandstone. 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, some- 
 times bound together into a solid rock, are found in great abundance 
 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 continuous 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 con- 
 sist throughout of rounded and angular fragments of granite, quartz, 
 
 * Scrope, Geology of Central France, p. 15. 
 
198 UPPER EOCENE PERIOD. [Cn. XV. 
 
 primary slate, and red sandstone. 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 ce- 
 ment. 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 advan- 
 tage of seeing a section continuously exposed for about 700 feet in thick- 
 ness. 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 imbed- 
 ded nodules. These sometimes constitute spheroidal concretions 6 feet in 
 diameter, and pass into beds of solid limestone, 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 iden- 
 tical in all their mineral characters with the secondary New Red sand- 
 stone 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 Al- 
 lier. The marls are sometimes of a purplish-red color, as at Champheix, 
 and are accompanied by a reddish limestone, like the well-known " corn- 
 stone," which is associated with the Old Red sandstone of English geol- 
 ogists. 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 Au- 
 vergne, 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 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 
 
CH. XV.] LACUSTRINE STRATA AUYERGNE. 199 
 
 amassed near the northern shores, so in Auvergne the grits and con- 
 glomerates before mentioned were evidently formed near the borders. 
 
 The entire thickness of these marls is unknown ; but it certainly ex- 
 ceeds, 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 innumerable thin shells, or 
 carapace-valves, of that small animal called Cypris. This animal is pro- 
 vided 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 inud, 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, form- 
 ing 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 finer 
 
 Fig. 177. 
 
 Vertical strata of marl, at Champradelle, near Clermont 
 
 A. Granite. B. Space of 60 feet, in which no section is seen. 
 
 C. Green marl, vertical and inclined. D. White marl. 
 
 mud only was drifted there by currents. The verticality of some of the 
 beds in the above section bears testimony to considerable local disturb- 
 ance 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 reg- 
 ular beds. 
 
 On each side of the basin of the Limagne, both on the west at Gan- 
 nat, and on the easjt at Vichy, a white oolitic limestone is quarried. At 
 
200 
 
 INDUSIAL LIMESTONE. 
 
 [On. XV. 
 
 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 combining both the radiated and concen- 
 tric structure. 
 
 Indusial limestone. There is another remarkable form of freshwater 
 limestone in Auvergne, called " indusial," from the cases, or inclusive, 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 calcareous, but there is occa- 
 sionally an intermixture of siliceous matter. Several beds of it are fre- 
 quently 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 6), near the base of the 
 hill of Gergovia ; and affords, 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. 
 
 Fi?. 178. 
 
 Bed of indusial limestone, interstratified with freshwater marl, near Clermont (Kleinschrod). 
 
 
 
 We may often observe in our ponds the Phryganea (or Caddice-fly), 
 .n its caterpillar state, covered with small freshwater shells, which they 
 Lave the power of fixing to the outside of their tubular cases, in order, 
 probably, to give them weight and strength. The individual figured in 
 
CH. XV,] EOCKlSrE PEKIOD. 201 
 
 the annexed cut, which belongs to a species very abundant in England, 
 j,. im 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 univalve of the genus Paludina. A 
 Larva of recent Phryganea.* hundred of these minute shells are some- 
 times 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, at right angles one to the other. When we consider 
 
 Fig. ISO. 
 
 a. Indusial limestone of Auvergne. 5. Fossil Paludina magnified. 
 
 that ten or twelve tubes are packed within the compass of a cubic inchj 
 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 integuments 
 and shells to compose this singularly constructed rock. It is unnecessa- 
 ry 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 witnessing 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. Kound the shallow 
 borders an abundant crop of reeds and rushes may be observed, covered 
 with the indusia of the Phryganea grandis and other species, to which 
 shells are attached. The plants which support them are the bullrush. 
 Scirpus lacustris, and common reed, Arundo phragmites, but chiefly the 
 former. In summer, especially 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 alone are wanting to form extensive beds of indusial 
 limestone, like those of Auvergne. 
 
 * I believe that the British specimen here figured is P. rhombica, Linn. 
 
202 LACUSTKINE STKATA AUVERGNE. [Cn. XV 
 
 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. Romain, 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 OB 
 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 can- 
 not be learnt by the study of any one section ; and the geologist who 
 sets out with the expectation of rinding a fixed order of succession may 
 perhaps complain that the different parts of the basin give contradictory 
 results. The arenaceous division, the marls, and the limestone, may aL 
 be seen in some places to alternate with each other ; yet it can by no 
 means be affirmed that there is no order of arrangement. The sands, 
 sandstone, and conglomerate constitute in general a littoral group ; the 
 foliated white and green marls, a contemporaneous 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 consider- 
 able thickness of quartzose sand or green marl. From the resemblance 
 of the limestones to the Italian travertins, we may conclude that they 
 were derived from the waters of mineral springs, such springs as even 
 now exist in Auvergne, and which may be seen rising up through the 
 granite, and precipitating travertin. They are sometimes thermal, but 
 this character 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, therefore, of lava 
 were transported into the lake, no fragments of volcanic rocks im- 
 bedded in the conglomerate. But at a later period, when a considerable 
 thickness of sandstone and marl had accumulated, eruptions broke out, 
 and lava and tuff were deposited, at some spots, alternately with the 
 lacustrine strata. It is not improbable that cold and thermal springs, 
 holding different mineral 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 anal- 
 ogous 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 mate- 
 rials must be arranged according to their size and weight, the coarser 
 near the shore, the finer at a greater distance from land ; but in the 
 
Ca XV.] UPPER EOCENE STRATA. 203 
 
 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 pro- 
 duce 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 precip- 
 itated 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 depression. 
 
 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 mammiferous fauna by 
 the labors 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 Cainotkerium, 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 Didelphys, a genus also found in the Paris gypsum, and 
 several forms of ruminants of extinct genera, such as Amphitragulas elegans 
 of Pomel, which has been identified with a Rhenish species from Weisse- 
 nau near Mayence, called by Kaup Dorcatkerium nanum ; other associ- 
 ated fossils, e. g., Microtherium Reuggeri, and a small rodent, Titanomys, 
 are also specifically the same with mammalia of the Mayence basin. The 
 Hycenodon, a remarkable carnivorous 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, Hycenodon, 
 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. 
 
 Cantal A freshwater formation, of about the same age and very 
 analogous to that of Auvergne, is situated in the department of Haute 
 
204 UPPER EOCENE STRATA CANTAL. [dr. XV. 
 
 Loire, near the town of Le Puy, in Velay ; and another occurs neat 
 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, com- 
 posed 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 calca- 
 reous marls, contains subordinately gypsum, silex, and limestone. 
 
 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 miperal character alone as a safe criterion of rela- 
 tive 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 mould. In these cavities we recog- 
 nize an exact counterpart to those which are so numerous on the fur- 
 rowed 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 neighborhood of Aurillac, hills of limestone and calcareous 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 color, like 
 the exterior of the flinty nodules of our chalk. 
 
 The abundant supply both of siliceous, calcareous, and gypseous mat- 
 ter, which the ancient lakes of France received, may have been connected 
 with the subterranean volcanic agency of which those regions were so 
 long the theatre, and which may have impregnated the springs with min- 
 eral 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 solu- 
 tion ; and it has been lately affirmed, that steam at a high temperature is 
 capable of dissolving quartzose rocks without the aid of any alkaline or 
 other flux.* Warm wa.ter charged with siliceous matter would immedi- 
 ately part with a portion of its silex, if its temperature was lowered by 
 mixing with the cooler waters of a lake. 
 
 * See Proceedings of Royal Soc., No. 44, p. 288. 
 
Cir. XV.] SLOWNESS OF DEPOSITION. 205 
 
 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 composition 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 man- 
 ner, the extreme slowness with which the materials of the lacustrine 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 some- 
 times myriads of small Paludince and other freshwater shells. These 
 minute foliations of the marl resemble precisely some of the recent lamina- 
 ted beds of the Scotch marl lakes, and may be compared to the pages of 
 a book, each containing 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 composi- 
 tion and color, 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 sev- 
 eral hills in the neighborhood 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.* 
 
 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 aggre- 
 gate ; 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 containing the remains of myriads of tes- 
 tacea 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 neighborhood of Aurillac, are 
 themselves equally the result of successive accumulation, consisting of 
 reiterated sheets of lava, showers of scorise, 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. 
 
 Bourdeaux, Aix, &c. The Upper Eocene Strata in the Bourdeaux 
 
 * Lyell and Murchison, sur les Dep&ts Lacustres Tertiaires du Cantal, Ac. Ana 
 des ScL Nat. Oct. 1829. 
 
206 UPPER EOCENE OF NEBRASKA, U. S. [On. XV. 
 
 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 men- 
 tioned ; two of Archceotherium, a pachyderm allied to Chceropotamus 
 and Hyracotherium ; also Poebrotherium, an extinct ruminant allied to 
 Dorcatherium, Kaup ; also Agriochoegus of Leidy, a ruminant allied 
 to Merycopotamus of Falconer and Cautley ; and, lastly, a large car- 
 nivorous animal of the genus Machairodus, 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. 
 
CH. XVI.1 
 
 MIDDLE EOCENE FORMATIONS. 
 
 207 
 
 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, mummulites, 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 Gyp- 
 seous series of Montmartre and extinct quadrupeds Calcaire grossier Milio- 
 lites 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, part of 
 
 Fig. 181. 
 Map of the principal tertiary basins of the Eocene period. 
 
 IHypogene rocks and strata 
 older than the Devonian 
 or Old Eed 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. 
 
 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 insignificant. 
 
 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 Hampshire 
 basins. (See also Table, p. 104, et seq.) 
 
203 ENGLISH MIDDLE EOCENE FORMATIONS. [On. XVI. 
 
 UPPER EOCENE. 
 
 Thickness. 
 
 A. Hempstead beds, Isle of Wight, see above, p. 192 - - 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. 8. 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 Bognor beds, London and Hants 
 
 basins 360 to 600 
 
 C. 2. Plastic and Mottled Clays and Sands (Woolwich and Reading 
 
 series), London and Hants basins 100 
 
 C. 3. Thanet Sands, Reculvers, 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 Osbome 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. 187), pass upwards into the Hempstead beds, with which 
 they are conformable, near Yarmouth, in the Isle of Wight. They con- 
 sist of marls, clays, and limestones of freshwater, brackish, and marine 
 01 igin. Some of the most abundant shells, as Cyrena semistriata var., 
 and Paludina, lenta (fig. 175, p. 193), 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 turritissima, Forbes. Fragment of Carapace of Triony. 
 
 Bembridge. 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, (fee. 
 
 d. Bembridge limestones, compact cream-colored limestones alternating with 
 
CH. XVI] FLUVIO-MAKIXE SERIES IN ISLE OF WIGHT. 
 
 209 
 
 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 ellip- 
 ticus (fig. 184), and Helix occlusa (fig. 185), are among its best-known laud- 
 
 Fig. 184. 
 
 Fig. 185. 
 
 Fig. 186. 
 
 ulimvA ellipticus, Sow. Helix occlusa, Edwards, 
 Bembridge Limestone, Sconce Limestone, 
 
 half natural size. Isle of Wight 
 
 Paludina orMcularis, Bembridge. 
 
 shells. Paludina orbicularis (fig. 186) is also of frequent occurrence. One of 
 the bands is filled with a little globular Paludina. Among the freshwater 
 
 Fig. 1ST. 
 
 Fig. 188. 
 
 Fig. 189. 
 
 Planorbis d iscus, Edwards. Bem- 
 bridge. 
 
 Lymnea longiscata, Brard. 
 
 Chara tuberculata. 
 Bembridse Lime- 
 stone, L of Wight. 
 
 pulmonifera, Lymnea longiscata (fig. 188) and Planorbis discus (fig. 187) are 
 e 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 ob- 
 tained 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 lime- 
 stone with numerous hollows caused by Cyrmce 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 mammalia char- 
 acteristic of the gypseous series of Paris, as Palceotherium magnum 
 
 14 
 
210 FLUVIO-MARINE SERIES IN ISLE OF WIGHT. [Cn. XVJ. 
 
 (fig. 191), P. medium, P. minus, P. mimimum, P. Fig. 190. 
 
 curium, P. crassum ; also Anoplotherium commune 
 
 (fig. 190), A., secundarium, Dichobune cervinum, and 
 
 Cheer opotamus 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. 
 
 1 90). Paleotherium magnum was of the size of a 
 
 horse, three or four feet high. The annexed woodcut 
 
 (fig. 191) is- one of the restorations whieh Cuvier at- Blnstead ' Isle of Wight 
 
 tempted of the outline of the living animal, derived from the study of the 
 
 Fig. 191. 
 
 Lower Molar tooth, 
 
 nat. size. 
 
 Anoplotherium com,' 
 mune. 
 
 Paleotherium magnum, Cuvier. 
 
 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 tes- 
 tacea ; 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 brack- 
 ish-water origin, and very variable in mineral character and thickness. 
 Near Hyde, it supplies a freestone much used for building, and called by 
 Professor 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, Melania, and Melanopsis, 
 as also of Cypris and the seeds of Cham. 
 
 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) characterizes the freshwater 
 deposits, just as the allied form, P. discus (fig. 187) does the Bembridge 
 limestone. The brackish-water beds contain Patomomya 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 
 Ores de Fontainebleau, or the Upper Eocene series. The prevalence of 
 
CH. XVI.] 
 
 SHELL OF THE HEADON SERIES. 
 
 211 
 
 salt-water remains is most conspicuous in some of the central parts of the 
 formation. Mr. T. Webster, in his able memoirs on the Isle of Wight, 
 
 Fig. 192. 
 
 Fig. wa 
 
 Planorbis eiuymphalui, Sow. 
 Headon HilL \ diam. 
 
 Helix Idbyrinthica, Say. Headon Hill, Isle of Wight ; 
 and Hordwell Cliff, Hants also recent. 
 
 first separated the wnole 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 
 Ceritkium concavum (fig. 196). Helix labyrinthica, Say (fig. 193), a 
 
 Fig. 194. 
 
 Fig. 195. 
 
 Fig. 196. 
 
 Neritina concava. 
 Headon Series. 
 
 Lymnea caudata. 
 Headon Beds. 
 
 Cerithium concavum. 
 Headon Series. 
 
 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 spe- 
 cies still living, though, as usual in such cases, having no local connection 
 with the actual geographical range of the species. 
 
 The lower and middle portion of the Headon series is also met with in 
 Hordwell Cliff (or Hordle, as it is often spelt), near Lymington, 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 call- 
 ing attention to the important fact that these vertebrata differ specifically 
 from those of the Bembridge beds. Among the abundant shells of Hord- 
 well are Paludina lenta and various species of Lymneus, Planorbis, 
 Melania, Cyclas, and Unio, Potomomya, Dreissena, &c. 
 
 * Bulletin, Soc. Geol. de France, 1852, p. 191. 
 
212 FLUVIO-MAKINE SEEIES IN HAMPSHIRE. [On. XVI. 
 
 Among the chelonians we find a species f 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 (Paleryx, 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 of the Isle of Wight. The bones of 
 several birds have been obtained from Hordwell, and the remains of quad- 
 rupeds. The latter belong to the genera Paloplotherium of Owen, Ano- 
 plotherium, Anthracotherium, Dichodon of Owen (a new genus discovered 
 by Mr. A. H. Falconer), Dichobunc, Spalacodon, and Hycenodon. The 
 latter offers, I believe, the oldest known example of a true carnivorous 
 mammal in the series of British fossils, although I attach very little the- 
 oretical 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 than 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 flourished on the earth during the Eocene 
 period. 
 
 Many of the marine shells of the brackish-water beds of the above 
 series, both in the Isle of Wight and Hordwell Cliff, are common to the 
 underlying Barton clay ; and, on the other hand, there are some fresh- 
 water shells, such as Cyrena obovata, which are common to the Bem- 
 bridge beds, notwithstanding the intervention of the St. Helen's series. 
 The white and green marls of the Headon series, and some of the accom- 
 panying limestones, often resemble the Eocene strata of France in mineral 
 character and color in so striking a manner, as to suggest the idea that 
 the sediment was derived from the same region or produced contempo- 
 raneously 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. 208). In one of 
 the upper and sandy beds of this formation Dr. Wright 
 found Chama squamosa in great plenty. The same sands Fi &- 197 - 
 contain impressions of many marine shells (especially in 
 Whitecliff Bay) common to the uppeY Bagshot sands 
 afterwards to be described. The underlying Barton clay 
 has yielded about 209 marine shells, more than half of 
 them, according to Mr. Prestwich, peculiar; and only 
 eleven common to the London clay proper (C. 1, p. 208), 
 being in the proportion of only 5 per cent. On the other 
 hand, 70 of them agree with the shells of the calcaire 
 grossier of France. It is nearly a century since Brander published, in 
 
CH XVI.] 
 
 FOSSILS OF THE BARTOX CLAY. 
 
 213 
 
 1766, an account of the organic remains collected from these Barton ana 
 Hordwell cliffs, and his excellent figures of the shells then deposited in 
 the British Museum are justly admired by conchologists for their accuracy. 
 
 SHELLS OF THE BARTON CLAY, HANTS. 
 
 Certain foraminifera called Nummulites begin, when we study the 
 tertiary formations in a descending order, to make their first appearance 
 
 Fig. 198. 
 
 Fig. 199. 
 
 Fig. 200. 
 
 Fig. 201. 
 
 Mitrascabra, Valuta ambigua. Typhi* punyens. Valuta athteta. Barton 
 
 and Bracklesbam. 
 
 Fig. 202. 
 
 Fig. 203. 
 
 Fig. 204. 
 
 Fig. 205. 
 
 TerebeUumfusi- TerebeUum con- 
 forme. Barton volutum. Lam. 
 and Bracklesham. Seraphs convolu- 
 tum, Montf. 
 
 Cardita globosa. 
 
 Crassatella sulcata. 
 
 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 the Bagshot beds are usually 
 
 * Prest-wich, Quart. Geol. Journ. vol. iii. p. 386. 
 
214 
 
 EOCENE BAGSHOT SANDS. 
 
 [CH. XVI. 
 
 devoid of fossils, they contain marine shells in some places, among which 
 Venericardia planicosta (see fig. 206) is abundant, with Turritella sul' 
 cifera and Nummulites Icevigata. (See fig. 210, p. 215.) 
 
 Fig. 206. 
 
 Venericardia planicosta^ Lam. 
 Cardita planicosta, Deshayes. 
 
 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 favor the idea 
 of a warm climate having prevailed, which is borne out by the discovery 
 of a serpent, Palceophis typhceus (see fig. 207), exceeding, according to 
 
 Fig. 207. 
 
 Palceophis typJimus, Owen ; jvn Eocene sea-serpent. Bracklesham. 
 | a, Z>. Vertebra, with long neural spine preserved. c. Two vertebrae in natural articulation. 
 
 Prof. Owen, 20 feet in length, and allied in its osteology to the Boa, Py 
 thon, Coluber, and Hydrus. The compressed form and diminutive size of 
 certain caudal vertebrae indicate so much analogy with Hydrus as to in- 
 duce 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, when the climate was 
 
 * Palseont. Soc. Monograph. Kept. pt. ii. p. fil 
 
CH. XVI.] 
 
 BRACKLESHAM BEDS. 
 
 215 
 
 probably more genial ; for amongst the companions of the sea-snake of 
 Bracklesham was an extinct Gavial (Gavialis Dixoni, Owen), and numer- 
 ous fish, such as now frequent the seas of warm latitudes, as the sword-fish 
 (see fig. 208), and gigantic rays of the genus Myliobates (see fig. 209). 
 
 Fig. 1208. 
 
 Prolonged premaxlllary bone or " sword" of a fossil sword-fish (Ccelorhynchui). Brackl*- 
 sham. Dixon's Fossils of Sussex, pi. 8. 
 
 Fig. 209. 
 
 Fig. 210. 
 
 Dental plates of Zfyliobatta Edicardsi. 
 Bracklesham Bay. Ibid. pL 8. 
 
 Nummulites (Num.mula.ria) Icevigata. 
 
 Bracklesham. Ibid. pL 8. 
 a. Section of the nnmnmlite. 
 &. Group, with an individual showing the exterior 
 
 The teeth of sharks also, of the genera Carcharodon, Otodus, Lamna, 
 Galeocerdo, and others, are abundant. (See figs. 211, 212, 213, 214.) 
 
 Fig. 211. 
 
 Fig. 212. 
 
 Fig.2ia 
 
 Fig. 214. 
 
 rcdarod<rr, \eterodon, Agass. Otodut oMquus, Agass. Lamna elegant, Galeocerdo latidens, 
 
 Agaes. Agass. 
 
 Teeth of sharks from Bracklesham Bay. 
 
 The Nummulites Icevigata (see fig. 210), so characteristic of the lower 
 beds of the calcaire Drossier in France, where it sometimes forms stony 
 layers, as near Compiegne, is very common at Bracklesham, together with 
 N. scabra and JV. 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. 
 
216 
 
 LOWER EOCENE STRATA OF ENGLAND. [On. XVI 
 
 MARINE SHELLS OF BRACKLESHAM BEDS. 
 Fig. 216. Fig. 21T. FIR. 218. 
 
 Pleurotoma atten- Valuta la- Turritella, Lucina serrata, Dison. Oonus deper* 
 uata, Sow. trella, Lam. multisuleata, Magnified. ditus. 
 
 Lam. 
 
 LOWER EOCENE FORMATIONS OF ENGLAND. 
 
 London Clay proper (C. 1, Table, p. 208). This formation underlies 
 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 Ro- 
 man cement. The principal localities of fossils in the London clay are 
 Highgate Hill, near London, the island of Sheppey, and Bognor in Hamp- 
 shire. Out of 133 fossil shells, Mr. Prestwich found only 20 to be com- 
 mon to the calcaire grossier (from which 600 species have been obtained), 
 while 33 are common to the " Lits Coquilliers" (p. 228), in which only 
 200 species are known in France. We may presume, therefore, that the 
 Condon 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 neighborhoods of London and Paris. 
 The fossL 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 resembles the 
 vegetation of the borders of the Mediterranean Fig. 220. 
 
 rather than that of an equatorial region ; whereas 
 the older flora of Sheppey belongs to an antece- 
 dent epoch, separated from the period of the Paris 
 gypsum by all the calcaire grossier and Bagshot 
 series in short, by the whole nummulitic forma- 
 tion properly so called. 
 
 Mr. Bowerbauk, 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 Wpa, now only 
 found in the Molucca and Philippine islands and Fossil palm of Sheppey. 
 in Bengal (see fig. 220). In the delta of the Ganges, Dr. Hooker ob- 
 served 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 
 
CH. XVL] FOSSILS OF THE LONDON CLAY. 217 
 
 steamboats. 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 considera- 
 ble 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 vegetable 
 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. 214), has also 
 been described by Professor Owen from Sheppey, of a different species 
 from that of Bracklesham. A true crocodile, also, Crocodilus toliapicus, 
 and another saurian more nearly allied to the gavial, accompany the 
 above fossils ; also the relics of several birds and quadrupeds. One of 
 these last belongs to the new genus Hyracotherium of Owen, allied to the 
 Hyrax, Hog, and Chseropotamus ; another is a Lophiodon ; a third, a 
 pachyderm called Coryphodon eoccenus by Owen, larger than any existing 
 tapir. All these animals seem to have inhabited the banks of the great 
 river which floated down the Sheppey fruits. They imply the existence of 
 a mammiferous fauna antecedent to the period when nummulites flour- 
 ished 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 derivable 
 from the plants and reptiles in favor of a high temperature. Thus many 
 species of Conus and Valuta occur, a large Cyprcea, C. oviformis, a very 
 large Rostellaria (fig. 223), a species of Canctllaria, six species of Nau- 
 tilus (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 
 angulatus (fig. 228), and among the Eadiata a star-fish called Astropec- 
 ten (fig. 229). 
 
 These fossils are accompanied by a sword-fish (Tetrapterus priscus, 
 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 described by M. 
 Agassiz from these beds in Sheppey, and they indicate, in his opinion, a 
 warm climate. 
 
 * For description o^ Eocene Cephalopoda, see Monograph by F. R Edwards, 
 Palaeontograph. Soc. 1849. 
 
218 
 
 FOSSIL SHELLS OF THE LONDON CLAY. [Cn. XVI. 
 
 FOSSIL SHELLS OF THE LONDON CLAY. 
 Fig- 221. Fig. 222. Fig. 228. 
 
 Voluta nodosa, Sow. Phorus extensus, 
 
 Highgate. Sow. Highgate. 
 
 Fig. 224. 
 
 Nautilus centralis^ Sow. Highgate. 
 Tig. 225. 
 
 Aturia eicsac, Brown and Edwards. 
 
 Syn. Nautilus ziczac, Sow. 
 
 London clay. Sheppey. 
 
 Rostellaria macroptera, Sow. One- 
 third of nat. size ; also found in the 
 Barton clay. 
 
 Fig. 226. 
 
 Belosepia sepioidea. Do Blainv. 
 London clay. Sheppey. 
 
 Fig. 227. Fig. 228. 
 
 Leda amygdaloides, 
 Highgate. 
 
 Axinus angulatus. London 
 clay. Horusea. 
 
 Fig. 229. 
 
 Astrfipecten crispatus, 
 E. Forbes. Sheppey. 
 
 Strata of Kyson in Suffolk. At Kyson, a few miles east of Wood- 
 bridge, a bed of Eocene clay, 12 feet thick, underlies the red crag. 
 Beneath it is a deposit of yellow and white sand, of considerable interest, 
 in consequence of many peculiar fossils contained ni it. Its geological 
 position is probably the lowest part of the London clay proper. In this 
 
CH. XVI] STRATA OF KYSON IN SUFFOLK. 219 
 
 sand has been found the first example of a fossil quadrumanous animal 
 discovered in Great Britain, namely, the teeth and rig. 230. 
 
 part of a jaw, shown by Professor Owen to belong 
 to a monkey of the genus Macacus (see fig. 230). 
 The mammiferous fossils, first met with in the Molar of monkey (Macacus). 
 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. Mr. Colchester in 1840 obtained Fi 031 
 
 other mammalian relics from Kyson, among 
 which Professor Owen has recognized several 
 teeth of the genus Hyracotherium, and the ver- 
 tebrae of a large serpent, probably a Palceophis. 
 As the remains both of the Hyracotherium and 
 Palceophis were afterwards met with in the Lon- opossum. "From Kyson! 
 don clay, as before remarked, these fossils con- 
 firmed the opinion previously entertained, that 
 the Kyson sand belongs to the Eocene period. 
 The Macacus, therefore, constitutes the first exam- 
 ple of any quadrumanous animal occurring in strata 
 
 u J / i. Molars of insectivorous bats, 
 
 so old as the Eocene, or m a spot so far from the twice nat. size, 
 
 equator as lat. 52 K It was not until after the ' Ky80D ' 8u 
 
 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. 208). 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 Prestwich) are used 
 for the like purposes in England.f 
 
 No formations can be more dissimilar on the whole in mineral char- 
 acter than the Eocene deposits of England and Paris ; those of our own 
 island being almost exclusively of mechanical origin, accumulations of 
 mud, sand, and pebbles ; while in the neighborhood of Paris we find a 
 great succession of strata composed of limestones, some of them 
 siliceous, and of crystalline gypsum and siliceous sandstone, 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, Water-bearing strata of London, 1851. 
 
220 
 
 LOWER EOCENE STRATA OF ENGLAND. [On. XVI 
 
 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 ot 
 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 New Haven in 
 Sussex, and elsewhere, a mixture of marine and freshwater testacea dis- 
 tinguishes this member of the series. Among the latter, Milania inqui- 
 nata (see fig. 234) and Cyrena cuneiformis (see fig. 233) are veiy corn- 
 
 Fig, 233. 
 
 Fig. 234 
 
 Cyrena, cuneiformis, Min. Con. 
 Natural size. 
 
 Melania inquinata, Des. Nat. size. 
 Syn. Cerithium melanoides, Min. Con. 
 
 mon, 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 sometimes, as at Woolwich, 
 
CH. XVI] PLASTIC CLAYS AND SANDS. 221 
 
 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 Conda- 
 mine discovered in 1849, and pointed out to me, a layer of sand asso- 
 ciated 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 de- 
 scribed* a bank of sandy mud, in the delta of the Alabama river at 
 Mobile, on the borders of the Gulf of Mexico, where in 1846 I dug 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 Gyrenes 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 
 character ; while in an opposite, or southwestern 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 southwest 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 pe- 
 riods, and the consequent change from shallow to deep water, the fresh- 
 water and littoral character of this inferior group appeared strange and 
 anomalous. After passing through hundreds of feet of London clay, 
 pro ?ed by its fossils to have been deposited in deep salt water, we arrive 
 at oeds of fluviatile origin, and in the same underlying formation masses 
 of shingle, attaining at Blackheath, 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. 208), 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. 208). The mottled or plastic clay of the 
 
 * Second Visit to the United States, yoL il p. 101. 
 
222 EOCENE STEATA IN FKANCE. [Cn. XVI. 
 
 Isle of Wight and Hampshire is often seen in actual contact with the 
 chalk, constituting in such places the lowest member of the British Eo- 
 cene 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 longirostris, Scalaria Bowerbankii, &c. The greatest thickness 
 of these beds is about 90 feet. 
 
 FRENCH MIDDLE EOCENE FORMATIONS. 
 GENERAL TABLE OF FRENCH EOCENE STRATA. 
 
 A. TJPPEK EOCENE (Lower Miocene of many French authors.) 
 
 English Equivalents. 
 
 A. Calcaire de la Beauce, or upper fresh- ) 
 
 water, see p. 184, and Gres de Fon- >Hempstead series, see p. 192. 
 tainebleau, <fcc. ) 
 
 B. MIDDLE EOCENE. 
 
 B. 2. Calcaire siliceux, (in. part eontem- 1 
 
 poraneous with the succeeding > Lower part of the Bembridge series. 
 group ?) ) 
 
 , 3. Grde Beaucha^p, ov Sables 
 
 i Lower Bagshot. Intermediate in age 
 between the Bracklesham beds and 
 London Clay. 
 
 C. LOWER EOCENE. 
 
 c. Argile plastique et lignite. 
 
 The tertiary formations in the neighborhood of Paris consist of a 
 series of marine and freshwater strata, alternating with each other, and 
 filling 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. 195). MM. Cuvier and Brongniart attempted, in 
 1810, to distinguish five different groups, comprising three freshwater 
 
CH. XVI] MIDDLE AND LOWEK EOCENE OF FRANCE. 223 
 
 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 Hamp- 
 shire and London basins have rather tended to confirm these views, at 
 least so far as to show, that since the commencement of the Eocene 
 period there have been great movements of the bed of the sea, and of 
 the 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 si- 
 multaneously 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. 222. 
 
 Beneath the Upper Eocene or " Upper marine sands," A, already 
 spoken of (p. 194), we find, in the neighborhood 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 carcasses, clothed with their flesh and skin, had 
 been floated down soon after death, and while they were still swoln by 
 the gases generated by their first decomposition. The few accompany- 
 ing 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 sul- 
 phate 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 j 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. 
 
224 GYPSEOUS SERIES. [Cn. XVI. 
 
 destroying, by its noxious properties, all the vegetation.* In like manner 
 the Pusanibio, or " Vinegar Kiver," of Colombia, which rises at the foot 
 of Purace, an extinct volcano, 7,500 feet above the level of the sea, is 
 strongly impregnated 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, in- 
 cluding 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 Jfycenodon dasyuroides, and a species of dog, Canis 
 Parisiensis, and a weasel, Cynodon Parisiensis. Of the JKodentia, are 
 found a squirrel ; of the Insectivora, 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.J 
 The same remark applies to the fish, according to MM. Cuvier and 
 Agassiz, as also to the reptiles. Among the last are crocodiles and tor- 
 toises of the genera Emis 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. 210). 
 These were associated with the Anoplotherium, a tribe intermediate be- 
 tween 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 ex- 
 tinct, 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 before maintained that the shells 
 
 * Leyde Magaz. voor Wetensch Konst en Lett, partie v. cahier i. p. 71. Cited 
 by Rozet, Journ. de Geologie, torn. i. p. 43. 
 
 f M. C. Prevost, Submersions Iteratives, <fec. Note 23. 
 j Cuvier, Oss. Fosa., torn. iii. p. 255. 
 
CH. XVI] 
 
 CALCAiRE SILICEUX. 
 
 and zoophytes, met with in many ancient European rocks, had ceased to 
 be inhabitants of the earth, but the majority even of the educated classes 
 
 Fig. 235. 
 
 Xiphodon gracilt, or Anoplotherium gracile, Curler. Eestored outline. 
 
 continued to believe that the species of animals and plants now contem- 
 porary 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 crea- 
 tures previously 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 publication of 
 Cuvier's Ossements Fossiles, and still more his popular Treatise 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 Mont- 
 martre 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 unexplored, 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 precipitate from 
 the waters of mineral springs, and is often traversed by small empty 
 sinuous cavities. It is, for the most part, devoid of organic remains, 
 but in some places contains freshwater and land species, and never any 
 marine fossils. The siliceous limestone and the caleaire grossier usually 
 occupy distinct parts of the Paris basin, the one attaining its fullest de- 
 velopment 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 con- 
 cludes, that while to the north, where the Bay was probably open to the 
 
 15 
 
CALCAIRE GROSSIER. [Ca XVL 
 
 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 sup- 
 posed that during the Eocene period, as now, the ocean was to the north, 
 and the continent, where the great lakes existed, to the south. From that 
 southern region we may suppose a body of freshwater to have descended, 
 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 gros- 
 sier 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 de- 
 scending from the east may have brought down the gypseous and marly 
 sediment. 
 
 Gris 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, con- 
 tain more than 300 species of marine shells, many of them peculiar, but 
 others common to the next division. 
 
 Calcaire grossier, 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, Paleo- 
 therium and Lophiodon, have been found. The middle division, or cal- 
 caire grossier proper, consists of a coarse limestone, often passing into 
 sand. It contains the greater number of the fossil shells which character- 
 ize the Paris basin. No less than 400 distinct species have been pro- 
 cured from a single spot near Grignon, where they are imbedded in a 
 calcareous sand, chiefly formed of comminuted shells, in which, never- 
 theless, individuals in a perfect state of preservation, both of marine, 
 terrestrial, and freshwater species, are mingled together. Some of 
 the marine shells may have lived 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 
 Cerithia 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 limestone, called calcaire siliceux, already 
 
CH XVL] 
 
 EOCENE FORAMINIFERA. 
 
 227 
 
 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 wood- 
 cut. As this miliolitic stone never occurs in the Faluns, or Miocene strata 
 
 EOCENE FORAMINIFERA. 
 
 Fig. 236. 
 
 Fig. 237. 
 
 Calcarina rarispina, Desh. 
 b. Natural size. a. e. Same magnified. 
 
 SjArolina etenostoma, Desh. 
 B. Natural size. A, C. D. Same magnified. 
 
 Fig. 238. 
 
 TrilocvUna injtata, Desh. 
 &. Natural size. a, e, d. Same magnified. 
 
 Fig. 239. 
 
 ClavuHna comtgata, Desh. 
 Natural size. 5, e. Same magnified. 
 
 of Brittany and Tourame, it often furnishes the geologist with a useful 
 criterion for distinguishing the detached Eocene and Miocene forma- 
 tions, scattered over those and other adjoining provinces. The dis- 
 covery of the remains of Paleotherium and other mammalia in some 
 of the upper beds of the calcaire grossier shows that these land animals 
 began to exist before the deposition of the overlying gypseous series 
 had commenced. 
 
228 
 
 LITS COQUILLIEES. 
 
 [Cn. XVI 
 
 Lower Calcaire grassier, or Glauconie grossier e, B. 5. The lower part 
 of the calcaire grossier, which often contains much green earth, is char- 
 acterized at Auvers, near Pontoise, to the north of Paris, and still more 
 in the environs of Compiegne, by the abundance of nummulites, con- 
 sisting chiefly of N. Icevigata, N. scabra, and N. Lamarcki, which con- 
 stitute 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 preceding 
 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 peculiar. The Nummulites 
 planulata is very abundant, and the most characteristic shell is the 
 Nerita conoidea, Lam., a fossil which has a very wide geographical 
 
 Fig. 240. 
 
 Iferita conoidea, Lam. 
 Byn. 2f. Schmidelliana, Chemnitz. 
 
 range ; for, as M. D'Archiac remarks, it accompanies the nummulitic for- 
 mation from Europe to India, having been found in Cutch, near the 
 mouths of the Indus, associated with Nummulites 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 inferieures" 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 
 unrepresented 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 
 
 Fig. 241. 
 
 Cardium porulosum. Paris and London basins, 
 * D'Archiac, Bulletin, torn. x. ; and Prestwich, Geol. Quart. Journ. 1847, p. 371 
 
CH. XVI.] NUMMULITIC FORMATIONS. 229 
 
 an example of the changes which certain species underwent in the succes- 
 sive staares of their existence. It seems that different varieties of the 
 
 O 
 
 Cardium porulosum are characteristic of different formations. In the 
 Soissonnais this shell acquires but a small volume, and has many pecu- 
 liarities, 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 modifications of form are preserved throughout the " upper 
 marine" (or Upper Eocene) series.* 
 
 Argile plastique (C, Table, p. 222). 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 ( Ostrea 
 bellovacina) abound in some places, and in others there is a mixture of 
 fluviatile shells, such as Cyrena cuneiformis (fig. 233, p. 220), Melanin 
 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 straw 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 lit- 
 toral origin, and imply the previous emergence of the chalk, and its waste 
 by denudation. 
 
 Whether the Thanet sands before mentioned (p. 221) are exactly rep- 
 resented in the Paris basin, is still a matter of discussion. 
 
 Wide extent of the nummulitic formation in Europe, Asia, <&c. When 
 I visited Belgium and French Flanders in 1851, with a view of com- 
 paring 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, JV. variolaria in the 
 upper beds, N. loevigata 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'Archiac. The same author, in the valuable 
 monograph recently published by him,f has observed, that a somewhat 
 similar distribution of these and other species in time, prevails very 
 widely in the South of France and the Pyrenees, as well as in the Alps 
 and Apennines, and in Istrea, 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 upper- 
 most 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 char- 
 
 * Coquilles caract&ristiques des terrains, 1831. 
 
 f Animaux foss. du groupe nummul. de 1'Inde : Paris, 1853. 
 
230 NUMMULITIC FORMATIONS IN EUROPE, ETC, [On. XVI. 
 
 acteristic 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 
 regarded 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-colored slates, 
 marls, and fucoidal sandstones, to the whole of which the provincial name 
 of " flysch" has been given in parts of Switzerland. 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 com- 
 paratively 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 Car- 
 pathians, 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 far- 
 ther eastward into India, as far as eastern Bengal and the frontiers of China. 
 
 Fig. 242. 
 
 Nummulites Puschi, D'Archlac. Peyrehoradc, Pyrenees. 
 
 a. External surface of one of the nummulites, of which longitudinal sections are seen in the 
 
 limestone. 
 T>. Transverse section of same. 
 
CH. XVL] EOCENE STRATA. 
 
 Dr. T. Thomson found nummulites at an elevation of no less than 
 1 6,500 feet above the level of the sea, in Western Thibet. 
 
 One of the species, which I myself found very abundant on the flanks 
 of the Pyrenees, in a compact crystalline marble Fig. 248. 
 
 (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 Sylhet, on the 
 frontiers of China. *"*' Europe "* Indta - 
 
 In many of the distant countries above alluded to, in Cutch, for exam- 
 ple, some of the same shells, such as Nerita conoidea (Hg. 240), accom- 
 pany 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 confound- 
 ing an allied genus, Orbitoides, with the true Nummulite. 
 
 When we have once anived at the conviction that the nummulitic for- 
 mation 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, Carpa- 
 thians, 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 nummulites and their accompanying tes- 
 tacea were unquestionably inhabitants of salt water. Before these events, 
 comprising the conversion of a wide area from a sea to a continent, Eng- 
 land had been peopled, as I before pointed out (p. 219), by various 
 quadrupeds, by herbivorous pachyderms, by insectivorous bats, by opos- 
 sums and monkeys. 
 
 Almost all the extinct volcanoes which preserve any remains of their 
 oriafinal form, or from the craters of which lava streams can be traced, 
 
 O 
 
 are more modern than the Eocene fauna now under consideration ; and 
 besides these superficial monuments of the action of heat, Plutonic influ- 
 ences 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 crys- 
 talline 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 iraced southwards from Delaware and Maryland to Georgia and 
 
 * Mnrchison, Quart. Journ. of Geol. Soc. vol. v., and Lyell, vol. vl 1850, Anni- 
 versary Address. 
 
232 EOCENE STKATA IN UNITED STATES. [Cfl. XVI 
 
 Alabama. The} 7 also occur in Louisiana and other states both east and 
 west of the valley of the Mississippi. At Claiborne in Alabama no less 
 than 400 species of marine shells, with many echinoderms and teeth of 
 fish, characterize one member of this system. Among the shells, the 
 Cardita planicosta, before mentioned (fig. 216, p. 214), 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.j 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 forma- 
 tion of India. The following section will enable the reader to understand 
 the position of three subdivisions of the Eocene series, Nos. 1, 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. V Eocene. 
 
 3. Orbitoidsl, 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 representative 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 pe- 
 culiar 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 argillaceous, 
 
 * See paper by the author, Quart. Journ. Geol. Soc. vol. iv. p. 12; and Second 
 Visit to the U. S. vol. ii. p. 59. 
 f Quart. Journ. Geol. Soc. vol. vi. p. 32. 
 
CH. X.VI.J EOCENE STKATA IN UNITED STATES. 233 
 
 but in parts very compact and calcareous. It contains several peculiar 
 corals, and a large Nautilus allied to ^V. ziczac ; also in its upper bed a 
 gigantic cetacean, called Zeuglodon by Owen.* 
 
 Fig. 245. Fig. 246. 
 
 Zeuglodon cetoides, Owen. 
 Sasilosaurus, 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 vertebral 
 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 dis- 
 tance 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. Wyrnan 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 an- 
 other fossil species of the same family, having the double occipital con- 
 dyles 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 : Spon- 
 dylus dumosus (Plagiostoma dumosum, Morton,) Pecten Poulsoni, 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. 232), formerly supposed 
 to be a nummulite, and called W. Mantelli, mixed -with a few lunulites, 
 some small corals, and shells.f The origin, therefore, of this cream- 
 colored soft stone, like that of our white chalk, which it much resembles, 
 is, I believe, due to the decomposition of these foraminifera. The surface of 
 the country where it prevails is sometimes marked by the absence of wood, 
 
 * See Memoir by R. W. Gibbes, Journ. of Acad. Nat. Sci. Philad. voL i. 1847. 
 f Lyell, Quart. Journ. GeoL Soc. 1847, voL iv. p. 15. 
 
234: CKETACEOUS GROUPS. [On. XV Q 
 
 like our chalk downs, or is covered exclusively by the Juniperus Virgini- 
 ana, 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. 232) that the strata of 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 formation, 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 rela- 
 tions 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 color, 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 Northwestern 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 Green- 
 sand 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, commonly called 
 the chalk, or the cretaceous strata, from creta, 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 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 
 
CH. XVIL] PISOLITIC LIMESTONE OF FRANCE. 235 
 
 between 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 com- 
 paratively 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 dis- 
 tinct and characteristic a fauna, as may entitle them to hold an indepen- 
 dent 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 Eo- 
 cene. To the same tertiary series belong the Belgian formations, called 
 by Professor Dumont, Landenian and Heersian, although these are prob- 
 ably 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 provin'ce of Hesbaye, in Belgium, where they 
 supply a durable building-stone, yet one so light as to be easily trans- 
 ported. 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 glau- 
 conite 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 
 
 Pisolitic limestone of France. Geologists have been still more at 
 variance respecting the chronological relations of this rock, which is 
 met with in the neighborhood of Paris, and at places north, south, 
 east, and west of that metropolis, as between Vertus and Laversines, 
 Meudon and Montereau. It is usually in the form of a coarse yellow- 
 ish or whitish limestone, and the total thickness of the series of beds, 
 
236 CLASSIFICATION OF CEETACEOUS ROCKS. [On. XVIL 
 
 already known is about 100 feet. Its geographical range, according tc 
 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, rest- 
 ing 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 paleontologists, and among others MM. C. D'Orbigny, 
 Deshayes, and D'Arcniac, disputed this conclusion, and, after enumerating 
 54 species of fossils, declared that their appearance was more tertiary than 
 cretaceous. More recently, M. Heb&rt having found the Pecten quadri- 
 costatus, 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 found, affords an additional indi- 
 cation of the two deposits being widely separated in time. The pisolitic 
 formation, therefore, may eventually prove to be somewhat more inter- 
 mediate 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 remark- 
 able 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, distin- 
 guished by peculiar fossils, and sometimes retaining a uniform mineral 
 character throughout wide areas. The Upper series is often called famil- 
 iarly the chalk, and the Lower the greensand, the last-mentioned name 
 being derived from the green color imparted to certain strata by grains 
 of chloritic matter. The following table comprises the names of the sub 
 divisions most commonly adopted : 
 
 UPPER CRETACEOUS. 
 
 A. 1. Maestricht beds and Faxoe limestones. 
 
 2. White chalk with flints. 
 
 3. Chalk marl, or gray chalk slightly argillaceous. 
 
CH, XVII] MAESTRICHT BEDS. 237 
 
 4. Upper greensand, occasionally with beds of chert, and with chlovitic 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 lime- 
 stone (Kentish Rag). 
 2. Wealden beds or Weald clay and Hastings sands.* 
 
 Maestricht Beds. On the banks of the Meuse, at Maestricht, reposing 
 on ordinary white chalk with flints, we find an upper calcareous 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 Belemnites 
 mucronatus (fig. 256, p. 245) and Pecten quadricostatus, a shell i- 
 garded by many as a mere variety of P. guinqztecostatus (see fig. 271). 
 Besides the Belemnite there are other genera, such as Baculite and Ha- 
 mite, never found in strata newer than the cretaceous, but frequently met 
 with in these Maestricht beds. On the other hand, Voluta, 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 yel- 
 lowish limestone 50 feet thick, extensively quarried from time immemorial 
 for building. The stone below is whiter, and contains occasional nodules 
 of gray 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, containing 
 green earth and numerous encrinital stems, which forms the line of de- 
 marcation between the strata containing the fossils peculiar to Maestricht 
 and the white chalk below. The latter is distinguished by regular layers 
 of black flint in nodules, and by several shells, such as Terebratula earned 
 (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 cele- 
 brated, occur both above and below that parting layer, and, among 
 others, the great marine reptile called Mosasaurus (see fig. 247), a sau- 
 rian supposed to have been 24 feet in length, of which the entire skull 
 
 * M. Alcide D'Orbigny, in his valuable work entitled Paleontologie Francaise, 
 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 . 
 
 Etage Danien. Maestricht beds. 
 
 Etage Senonien. White chalk, and chalk marl. 
 
 Etage Turonien. Part of the chalk marl. 
 
 Etage Cenomanien. Upper greensand. 
 
 Etage Albien. Gault. 
 
 Etage Aptien. Upper part of lower greensand 
 
 Etage Neocornien. Lower part of same. 
 
 Etage Neocornien 
 
 inferieur. Wealden beds and contemporaneous marine strata. 
 
238 CHALK OF FAXOE. [On. XVII. 
 
 and a great part of the skeleton have been found. Such remains are 
 chiefly met with in the soft freestone, the principal member of the 
 
 Fig. 247. 
 
 Mosasaurua eamperi. Original more than 8 feet long. 
 
 Maestricht beds. Among the fossils common to the Maestricht and white 
 chalk ma} 7 " be instanced the echinoderm (fig. 248). 
 
 I saw proofs of the previous denudation of the white chalk exhibited 
 in the lower bed of the Maestricht formation Fig. 248. 
 
 in Belgium, about 30 miles S. W. of Maestricht, 
 at the village of Jendrain, where the base of 
 the newer deposit consisted chiefly of a layer 
 of well-rolled, black, chalk-flint pebbles, in the 
 midst of which perfect specimens of Thecidea 
 radians and Belemnites mucronatus are im- 
 bedded, ffemipn&ustes radiatus, Ag. 
 
 Chalk of Faxoe. In the island of Seeland, Spatangus radio*** Lam. 
 
 , , ' Chalk of Maestricht and white 
 
 m Denmark, the newest member of the chalk chalk, 
 
 series, seen in the sea-cliffs at Stevensklint resting on white chalk with 
 flints, is a- yellow limestone, a portion of which, at Faxoe, where it is 
 used as a building-stone, is composed of corals, even more conspicuously 
 than is usually observed in recent coral reefs. It has been quarried to 
 the depth of more than 40 feet, but its thickness is unknown. The im- 
 bedded 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 Emarginula, 
 &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 Bacu- 
 lites Faujasii and Belemnites mucronatus, 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). 
 
CH. XVII] 
 
 WHITE CHALK. 
 Fig. 249. 
 
 rl 
 
 Nautilus Danicus, SchL Faxoe, Denmark. 
 
 The claws and entire skull of a small crab, Brachyu- 
 rus rugosus (Schlottheim), are scattered through the 
 Faxoe stone, reminding us of similar crustaceans in- 
 closed 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 sub- 
 stance must have been produced simultaneously ; 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, undistinguishable 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. 236, et seq.). 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 carbonate of lime ; the strati- 
 fication is often obscure, except where rendered distinct 
 by interstratified layers of flint, a few inches thick, occa- 
 sionally in continuous beds, but oftener in nodules, and 
 recurring at intervals from 2 to 4 feet distant from 
 each other. 
 
 This upper chalk is usually succeeded, in the descend- 
 ing order, by a great mass of white chalk without flints, 
 below which comes the chalk marl, in which there is a 
 slight admixture of argillaceous matter. The united 
 thickness of the three divisions in the south of England 
 equals, in some places, 1000 feet. 
 
 The annexed section (fig. 250) will show the man- 
 ner 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. 
 
240 ANIMAL ORIGIN OF WHITE CHALK. [Cur. XVII 
 
 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 de- 
 posits of recent date. Pure chalk, of nearly uniform aspect and compo- 
 sition, is met with in a northwest and southeast direction, from the north 
 of Ireland to the Crimea, a distance of about 1140 geographical miles, 
 and in an opposite direction it extends from the south of Sweden to the 
 south of Bourdeaux, 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 mucro- 
 natus, 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 sev- 
 eral 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 decomposing 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. 238, 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 struc- 
 ture 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 Capt. Nelson, that, in the Bermuda Islands, and in 
 the Bahamas, there are many basins or lagoons almost surrounded 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 with the exuviae of forarainifera, 
 

 
 CH. XVIL] AXIMAL ORIGIN OF WHITE CHALK. 241 
 
 mollusks, echinoderms, and crustaceans, 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 calca- 
 reous 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 graminivor- 
 ous quadrupeds. On opening their bodies, their rig. 251. 
 intestines were found to be filled with impure 
 chalk. This circumstance is the more in point, 
 when we recollect how the fossilist was formerly 
 puzzled by meeting, in chalk, with certain bodies, 
 called " larch-cones," which were afterwards rec- 
 ognized by Dr. Buckland to be the excrement of 
 fish. Such spiral coprolites (fig. 251), like the 
 scales and bones of fossil fish in 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 nar- 
 row openings leading from the lagoon to the ocean, and the waters of the 
 sea are discolored 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 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 aggre- 
 gated shells, imbedded in a compact calcareous base as firm in texture as 
 any secondary limestone ; while others are like chalk, having its color, 
 its earthy fracture, its soft homogeneous texture, and being an equally good 
 writing material. The same author describes, 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 currents, 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 southeast of England, of a few isolated pebbles of 
 
 * See Nelson, GeoL Trans. 1837, vol. v. p. 108 ; and GeoL Quart. Journ. 1853, 
 p. 200. 
 
 f Geol. of IT. S. Exploring Exped. p. 252, 1849. 
 
 16 
 
242 PEBBLES IN CHALK. [Ca XVU 
 
 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 
 was 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 fragtaent of green- 
 stone, where every other particle of matter was calcareous ; and Mr. Dar- 
 win 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, ob- 
 tained stones for sharpening their instruments by searching the foots 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 Fistulana.\ 
 
 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 buoy- 
 ant 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 white 
 
 * Darwin, p. 549. Kotzebue's First Voyage, vol. iii. p. 155. 
 f Mantell, Geol. of S. E. of England, p. 96. 
 
Cn. XVII.] CHALK FLINTS. 243 
 
 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 com- 
 position and organic remains the chalk marl of the English series. This 
 sandstone contains as many fossil shells common to our white chalk as 
 could be expected in a sea-bottom formed of such different materials. It 
 sometimes attains a thickness of 600 feet, and by its jointed structure and 
 vertical precipices, plays a 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 ac- 
 company 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 spiculae, 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 solu- 
 tion, such as the decomposition of felspathic rock (see p. 42), also min- 
 eral 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). Never- 
 theless, the occurrence in the white chalk of beds of nodular or tabular 
 flint at so many distinct levels, implies a periodical 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 rearrangement of its particles 
 to take place (the heavier silex sinking to the bottom) before the next 
 stratum was superimposed ; a process formerly suggested by Dr. Buck- 
 land* 
 
 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 about three feet in height, and one foot in their 
 
 * Geol. Trans., First series, vol. iv. p. 413. 
 
244: 
 
 POTSTONES AT HORSTEAD. 
 
 [On. XVII 
 
 transverse diameter, placed in vertical rows, like pillars at irregular dis- 
 tances from each other, but usually from 20 to 30 feet apart, though some- 
 
 Fig. 252. 
 
 From a drawing by Mrs. Gunn. 
 Yiew of a chalk.pit at Horstead, near Norwich, showing the position of the potstones. 
 
 times nearer together, as in the above sketch. These rows did not ter- 
 minate 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 cylindrical 
 nucleus of pure chalk, much harder than the ordinary surrounding chalk, 
 and not crumbling to pieces like it, when exposed to the winter's frost. 
 At the distance of half a mile, the vertical piles of 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 An- 
 trim, in Ireland.* 
 
 FOSSILS OF THE UPPER CRETACEOUS ROCKS. 
 
 Among the fossils of the white chalk, echinoderms are very numerous ; 
 
 Fig. 258. 
 
 I 
 
 tt. 
 
 Ananchytes ovatus. White chalk, upper and lower. 
 a. Side view. 
 
 I. Bottom of the shell on which, both the oral and anal apertures arc placed ; 
 the anal being more round, and at the smaller end. 
 
 * Geol. Trans., First series, vol. iv. p. 413, "On Paramoudra," &c. 
 
Cs. XVII.] FOSSILS OF UPPER CRETACEOUS ROCKS. 
 
 245 
 
 and some of the genera, like Ananchytes (see fig. 253), are exclusively 
 cretaceous. Among the Ciinoidea, the Marsupite (fig. 260) is a charac- 
 
 Fig.254 
 
 Fig. 255. 
 
 Micr aster cor-anguinum. 
 White chalk. 
 
 GdUrites aXbogalerus. Lam. 
 White chalk. 
 
 teristic genus. Among the mollusca, the cephalopoda, or chambered 
 univalves, of the genera Ammonite, Scaphite, Belemnite (fig. 256), Bacu- 
 lite (257-259), and Tumlite (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. Bdemnites mucronatus. 
 
 b. Same, showing internal structure. Maastricht, Faxoe, and white chalk. 
 
 Baculites anceps. Upper grcensand, or chloritic marl, crate chloritee. France 
 A. D'Orb. Terr. Cret 
 
 Fig. 25S. 
 
 Fig. 259. 
 
 Portion ofBootilitss Faujasii. 
 
 Maestricht and Faxoe beds and white chalk, 
 
 Fig. 260. 
 
 Marsupites Mitteri. 
 White chalk. 
 
 Portion of Baculites anceps. 
 Maestricht and Faxoe beds and white chalk. 
 
 Fig. 261. 
 
 Scaphites aquali*. Chloritio 
 
 marl of Upper Greensand, 
 
 Dorsetshire. 
 
246 
 
 FOSSILS OF UPPER CRETACEOUS ROCKS. [Cu. XVtt 
 Fig. 262. Fig. 263. 
 
 a. Fragment of Turrilites costatus. 
 Chalk marl. 
 
 Turrilites costatus, 
 Chalk. 
 
 0. Same, showing the indented border 
 of the partition of the chambers. 
 
 Among the brachiopoda in the white chalk, the Terebratulce are very 
 abundant. These shells are known to live at the bottom of the sea, where 
 
 Fig. 264. 
 
 Fig. 265. 
 
 Fig. 267. 
 
 Terebratula Defrancii. 
 Upper white chalk. 
 
 Terebratula 
 
 octoplicata. 
 
 (Var. of T. plioatilis.) 
 
 Upper white chalk. 
 
 Terebratula pumilus, Terebratula 
 (Magas purmlm, Sow.) carnea. 
 
 Upper white chalk. Upper white chalk. 
 
 the water is tranquil and of some depth (see figs. 264, 265, 266, 267, 
 268). With these are associated some forms of oyster (see figs. 275, 
 276, 277), and other bivalves (figs. 269, 270, 271, 272, 273). 
 
 Fig. 268. 
 
 Fig. 269. 
 
 Fig. 2TO. 
 
 Terebratula ftiplicata, 
 Bow. Upper cretaceous. 
 
 Crania Parisiensis, 
 inferior or attached 
 
 valve. 
 Upper white chalk. 
 
 Pecten Seaveri, reduced to 
 
 one-third diameter. 
 Lower white chalk and chalk 
 marl. Maidstone. 
 
 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 Lam.; see fig. 274), the shells 
 
CK. XVIL] FOSSILS OF UPPEK CKETACEOUS ROCKS. 
 
 247 
 
 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-costatvs. 
 White chalk, upper and 
 lower greensands. 
 
 Plagiostoma Hoperi, Sow. 
 
 Syn. Lima Boperi. 
 
 "White chalk 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 Europe, a 
 
 Fig. 274 
 
 Fig. 275. 
 
 Jnoceramus Lamarckii. 
 
 Syn. Catillus Lamarckii. 
 
 White chalk (Bixon's Geol. Sussex, Tab. 23, 
 
 fig. 29). 
 
 Ostrea veticularis. Syn. GrypTicea globosa. 
 Upper chalk and upper greensand. 
 
 single representative only (fig. 278) has been discovered in the white 
 chalk of England. 
 
 Fig. 276. 
 
 Ostrea columba. 
 
 Syn. Gryphcea columba. 
 
 Upper greensand. 
 
 Fig. 2T7. 
 
 Ostrea carinata. Chalk marl, upper and 
 lower greensand. 
 
248 
 
 MOLLUSCA, BKYOZOA, SPONGES. 
 Fig. 279. 
 
 [Cu. XVII 
 
 Jiadiolites Mortoni, Mantell. 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 s'.tuctuie. 
 
 281. Vertical section of the same. 
 
 On the side where the shell is thinnest, there is one external furrow and corresponding internal 
 ridge, #, &, 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 Hadiolites. 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 Eschara 
 and JEscharina (figs. 282, 283), which are alike marine, and, for the 
 
 Fig. 282. 
 
 EscJiarina oceani. 
 
 a. Natural size. 
 
 b. Part of the same magnified. 
 
 chalk. 
 
 Eschara disticha. 
 
 a. Natural size. 
 
 &. Portion magnified. 
 
 White chalk. 
 
 VentriculUes radiatus. 
 
 Mantell. 
 
 Syn. Ocellaria radiata, 
 D'Orb. White chalk. 
 
 most part, indicative of a deep sea. These and other organic bodies, es- 
 pecially sponges, such as VentriculUes (fig. 284) and Siphonia (fig. 286). 
 
CH. XVIL] FOSSILS OF THE UPPER CRETACEOUS BEDS. 
 
 249 
 
 are dispersed indifferently through the soft chalk and hard flint, and some 
 of the flinty nodules owe their irregular forms to inclosed sponges, such as 
 fig. 285 ct, where the hollows in the exterior are caused by the branches 
 of a sponge, seen on breaking open the flint (fig. 285 6). 
 
 Fig. 286. 
 
 Fig. 285. 
 
 A branching sponge in a flint, from the white chalk. 
 From the collection of Mr. Bowerbank. 
 
 Siphonia pyri- 
 formif, 
 
 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 
 
 Ptychodua decurrens. 
 
 Lower white chalk. 
 
 Maidstone. 
 
 Cestracion. Phillippi ; recent 
 Port Jackson. Buckland, 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 Shark, Oestracion 
 
250 UPPER GREENSAND. [Cn. XVII 
 
 Pktttippi, the anterior teeth of which (see fig. 288 a) are sharp and cut 
 ting, 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 con- 
 clude that the white chalk was the product of an open sea of considerable 
 depth. 
 
 The existence of turtles and oviparous saurians, and of a Pterodactyl or 
 winged lizard, found in the white chalk of Maidstone, implies, no doubt, 
 some neighboring land ; but a few small islets in mid-ocean, like Ascen- 
 sion, 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 in- 
 dication, 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, Man tell, 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 mistaken by able anat- 
 omists for those of birds ; of which class no osseous remains seern 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 lime- 
 stone and calcareous 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, contemporane- 
 ous 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 cretace- 
 ous 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 simultane- 
 ously, the one near the land, the other far from it, the san.ds in every 
 locality where a shore became submerged, might constitute the under- 
 lying deposit. 
 
 Gault. The lowest member of the upper Cretaceous group, usually 
 about 100 feet thick in the S. E. of England, is provincially termed 
 
CH. XVIL] 
 
 THE BLACKDOWN BEDS. 
 
 251 
 
 Gault. It consists of a dark blue rnarl, sometimes intermixed with green- 
 sand. Many peculiar forms of cephalopoda, such as the Hamite (fig. 291) 
 
 Fossils of the Upper Greenland. 
 Fig. 289. 
 
 Fig. 290. 
 
 a. Terebratiila lyra. ) Upper Greensand. 
 7* Same, seen in profile. J France. 
 
 IfettL 
 
 Ammonites Rhotomagentis. 
 Upper Greensand. 
 
 Hamites spiniger (Fitton) ; near Folkstone. Gault. 
 
 and Scaphite, with other fossils, characterize this formation, which, small 
 as is its thickness, can be traced by its organic remains to distant parts of 
 Europe, as, for example, to the Alps. 
 
 The Blackdown beds in Dorsetshire, celebrated for containing many 
 species of fossils not found elsewhere, have 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 de- 
 posited. Several Blackdown species are common to the Lower cretaceous 
 series, as, for example, Trigonia caudata, fig. 299. We learn from M. 
 D'Archiac, that in France, at Mons, in the valley of the Loire, strata of 
 greensand 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 abun- 
 dance 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, prob- 
 ably derived from the excrement of fish. 
 
 * Hist, des Progres de la Geol., <fec., vol. iv. p. 360, 1851. 
 
HIPPURITE LIMESTONE. 
 
 [On. XVIL 
 
 Fig. 292. 
 
 HIPPURITE LIMESTONE. 
 
 Difference between the chalk of the north and south of Europe. Bj 
 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 neighborhood 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 separates 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, Cida- 
 rites, 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 Hamite, Turrilite, and Scaphite, and perhaps 
 Belemnite, are entirely wanting. 
 
 On the other hand, certain forms are common in the south which are 
 rare or wholly unknown in the north of France. Among these may be 
 mentioned many Hippurites, Sphcerulites, and other members 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 the south of 
 
 * D'Archiac, stir la Form. Cre'tace'e du S. 0. de la France, Mem. de la Soc. Ge"oL 
 \e France, torn. ii. 
 
CH. XVIL] 
 
 CHALK OF SOUTH OF EUROPE. 
 
 253 
 
 France, Spain, Sicily, Greece, and other countries bordering the Mediter- 
 ranean. 
 
 Fig. 293. 
 
 Fig. 294. 
 
 a. Radiolitfs radiosrts, D'Orb. (Hippurites, Lam.) 
 />. Upper valve of same. 
 
 "White chalk of France. 
 
 Fig. 295. 
 
 BadioliteafoUaceus, D'Orb. 
 Syn. Sphcerulites agarici- 
 
 formis, Blainv. 
 White chalk of France. 
 
 Hippurite$ organisans, Desmoulins. 
 
 Upper chalk : chalk marl of Pyrenees?* 
 
 a. Young individual ; when full grown they occur in groups adhering 
 
 laterally to each other. 
 
 5. Upper Bide of the upper valve, showing a reticulated structure in 
 those parts, 6, 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 abundant 
 than any other in the south of Europe ; and the geologist should make- 
 himself well acquainted with the cast <?, 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 
 '.ength. 
 
 Between the region of chalk last mentioned, in which Perigueux is 
 
 D'Orbigny's PalSontologie Franchise, pi. 533. 
 
254: CRETACEOUS ROCKS. [Cn. XVII 
 
 situated, and the Pyrenees, the space B intervenes. (See Map, fig. 292.) 
 Here the tertiary strata cover, and for the most part conceal, the cre- 
 taceous 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 character 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 Hippurites. 
 
 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 referable, 
 paleontologically, to the same division. 
 
 Thf.t 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 overlying coralline limestone 
 of a pale yellow color, and the fossils, on the whole, agree most nearly 
 with those of the upper European series, from the Maestricht beds to the 
 gault inclusive. I collected sixty shells from the New Jersey deposits in 
 1841, five of which were identical with European species Ostrea larva, 
 0. vesicularis, 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 Inocera- 
 mus (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 tribe (Stenorhynchus vetus, Leidy), from 
 
 * See a paper by the author, Quart. Journ. Geol. See. vol. i. p. 79. 
 
Ca XVIL] CRETACEOUS ROCKS. 255 
 
 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 Mis- 
 sissippi, 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 ascer- 
 tained 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 calcareous 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. Eomer, the chalk assumes a new lithological 
 type, a large portion of it consisting of hard siliceous limestone, 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 Colum- 
 bia, as at Bogota, and elsewhere, containing Ammonites, Hamites, Inoce- 
 rami, and other characteristic shells.f 
 
 In the south of India, also, at Pondicherry, Verdachellum, and Trin- 
 conopoly, Messrs. Kaye and Egerton have collected fossils belonging 
 to the cretaceous system. Taken in connection with those from the 
 United States, they prove, says Professor E. Forbes, that those powerful 
 causes which stamped a peculiar character on the forms of marine animal 
 
 * In the Principles of Geology, ninth ed. p. 145, I cited Dr. Leidy, of Philadel- 
 phia, as having described (Proceedings of Acad. Nat. Sci. Philad. 1851) two 
 species of cetacea of a new genus which he called Priscodelphinus, from the 
 greensand of New Jersey. In 1853, 1 saw the two vertebrae at Philadelphia, 
 on which this new genus was founded, and afterwards, with the aid of Mr. Con- 
 rad, traced one of them to a Miocene marl pit in Cumberland county, New Jersey. 
 The other (the Plesiosaurus of Harlan), labelled " Mullica Hill" in the Museum, 
 would no doubt be an upper cretaceous fossil, if really derived from that 
 locality, but its mineral condition makes the point rather doubtful. The tooth 
 of Stenorhynchus veins, figured by Leidy from a drawing of Conrad's (Proceed, 
 of Acad. Nat. Sci. Philad. 1853, p. 377), was found by Samuel R. Wetherhill, 
 Esq., in the greensand 1 miles southeast of Burlington. This gentleman re- 
 lated to me and Mr. Conrad, in 1853, the circumstances under which he met 
 with it, associated with Ammonites placenta, Ammonites Delawarensis, Trigonia 
 thoracica, <fec. The tooth has been mislaid, but not until it had excited much 
 interest and had been carefully examined by good zoologists. 
 
 f Proceedings of the Gec4. Soc. vol. iv. p. 39 L 
 
256 LOWEK GREENS AND. [Cn. XVIII. 
 
 life at this period, exerted their full intensity through the Indian, Euro- 
 pean, 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 XVIII. 
 
 LOWER CRETACEOUS AND WEALDEN FORMATIONS. 
 
 Lower Greensand Term " N"eocomian"-rAtherfield section, Isle of Wight 
 Fossils of Lower Greensand Wealden Formation Freshwater strata interca- 
 lated 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 ap- 
 plied 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 with- 
 out reason, since green particles are wanting in a large part of the strata 
 so designated, even in England, and wholly so in some European coun- 
 tries. Moreover, a subdivision of the Upper Cretaceous group has like- 
 wise been called Greensand, and to prevent confusion the terms tipper 
 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 sub- 
 ordinate 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 Greensand 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 (or Greensand) formation as developed in England, 
 gives the following as the succession of rocks seen in parts of Kent. 
 
 * See Forbes, Quart. Geol. Journ. vol. i. p. 79. 
 
CH. XVIIL] ATHEKFIELD SECTION, ISLE OF WIGHT. 257 
 
 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 - - 60 to 80 feet. 
 
 In his detailed description of the fine section displayed at Atherfield, 
 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 thick- 
 ness of which he gives as 843 feet, there are some fossils which range 
 through the whole series, others which are peculiar to particular di- 
 visions. 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 cal- 
 careous bottom, or a moderate or a great depth of water, recur with 
 all the same species, the interval of time has been, geologically speak- 
 ing, small, however dense the mass of matter accumulated. But if, 
 the genera remaining the same, the species are changed, we have en- 
 tered upon a new period; and no similarity of climate, or of geo- 
 graphical 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 sys- 
 tems, 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 the large 
 Perna Mulleti, of which a reduced figure is here given (fig. 296). 
 
 * Dr. Fitton, Quart Geol. Journ., vol. L p. 179, ii. p. 55, and iii. p. 289, where 
 comparative sections and a valuable table showing the vertical range of the va- 
 rious fossils of the lower greensand at Atherfield are given. 
 
 17 
 
258 FOSSILS OF LOWER GREENSAND. [On. XVIII 
 
 Fig. 296. 
 
 Perna Mulleti. Desh. in Leym. 
 a. Exterior. &. 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 doubtless 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 specifically 
 distinct from those of the Upper Cretaceous strata. 
 
 Among the former we often meet with the genus Scaphites (fig. 297) 
 
 Fig. 297. 
 
 Fig. 293. 
 
 Nautilus plicatus, Sow.. 
 Fitton's Monog. 
 
 Scaphites gigaa, Sow. Syn. Ancyloceraa gigas, D'Orb. 
 
Cn. XVIII.] 
 
 WEALDEN" FORMATION. 
 
 259 
 
 or Ancyloceras, which has been aptly described as an ammonite more or 
 less uncoiled ; also a furrowed Nautilus, N. plicatus (fig. 298), Trigonia 
 caudata, likewise found in the Blackdown beds (see above, p. 251), and 
 Gcrvillia, a bivalve genus allied to Avicula. 
 
 Fig. 299. 
 
 Fig. 300. 
 
 Fig. 301. 
 
 Trigonia caudata, Agass. 
 
 GertiUia anceps, Desh. 
 
 Terebratitlasdla, Sow. 
 
 WEALDEN FORMATION. 
 
 Beneath the Lower Greensand in the S. E. of England, a freshwater 
 formation is found, called the Wealden (see Nos. 5 and 6, Map, fig. 320, 
 p. 271), which, although it occupies a small horizontal area in Europe, 
 as compared to the White Chalk and Greensand, is nevertheless 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. 271) ; 
 and we are indebted to Dr. Mantell for having shown, in 1822, in his 
 Geology of Sussex, that the whole group was of fluviatile origin. In 
 proof of* this he called attention to the entire absence of Ammonites, Be- 
 lemnites, TerebratulaB, Echinites, Corals, and other marine fossils, so char- 
 acteristic of the cretaceous rocks above, and of the Oolitic strata below, 
 and to the presence in the Weald of Paludinse, Melanin, and various flu- 
 viatile 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 phenomenon 
 with which we have since become familiar) was received, at first, with no 
 small doubt and incredulity. But the relative position of the beds is un- 
 equivocal ; the Weald Clay being distinctly seen to pass beneath the Lower 
 Greensand in various parts of Surrey, Kent, and Sussex, and to reappear 
 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. 
 
 Isle of Wight 
 
 , -Chalk 
 
 :>. Greensand. c. Weald Clay. d. Hastings Sand. e. Purbeck beds. 
 
260 WEALD CLAY. [Cte. XVIIT 
 
 The Wealden is di\ 7 isible into two minor groups : 
 
 Thickness. 
 1st. "Weald Clay, chiefly argillaceous, but 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 mollusks, Oypridet, 
 and other fossils, lies immediately beneath the Wealden in the southeast 
 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 encroach 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 OWE 
 times, we may suppose the bones of large alligators to be frequently en- 
 tombed 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 freshwater 
 beds had previously been formed ; and yet the Ganges might still pour 
 down its turbid waters in the same direction, and carry seaward the car- 
 cases of the same species of alligator, in which case their bones might be 
 included in marine as well as in subjacent freshwater strata. 
 
 The Iguanodon, first discovered by Dr. Mantell, has left more of its 
 remains in the Wealden strata of the southeastern counties and Isle of 
 Wight than has any other genus of associated saurians. It was an her- 
 bivorous reptile, and regarded by Cuvier as more extraordinary 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, a, 
 303, 6), to the modern Iguanas which now frequent the tropical woods 
 of America and the West Indies, exhibit many striking and important 
 differences. It appears that they have often been worn by the process of 
 mastication ; whereas the existing herbivorous reptiles clip and gnaw off 
 
 * Dr. Fitton, Geol. Trans. Second Series, vol. iv. p. 320. 
 
CH. XVIII] FOSSILS OF THE WEALDEN GROUP. 
 
 261 
 
 the vegetable productions 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 sur- 
 face (see fig. 304, 6), resembling the grinders of herbivorous mammalia. 
 
 Fig. 303. 
 
 Fig. 804 
 
 Fig. 303. a, &. Tooth of Iguanodon Mantetti. 
 Fig 304. . Partially worn tooth of young individual of the same, 
 &. Crown of tooth in adult, worn down. (MantelL) 
 
 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 magni- 
 tude from the reptile just burst from the egg, to one of which the femur 
 measured 24 inches in circumference. Yet, notwithstanding that the 
 teeth were more numerous than any other bones, it is remarkable that it 
 was not until the relics of all these 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 Oypris, a genus of Crustaceans before mentioned (p. 31) 
 as abounding in lakes and ponds, are also plentifully scattered 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. 199). 
 
262 FOSSILS OF THE WEALDEN GROUP. [On. XVIII. 
 
 Fig. 306. Fig. 806. Fig. 807. 
 
 Cypris 
 
 spinigera, 
 
 Fitton. 
 
 Cypris Valdensis, Fitton. 
 (C.faba, Min. Con. 4S5.) 
 
 Weald clay with Cypridcs. 
 
 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 sand- 
 stone and grit of Tilgate Forest, near Cuckfield, in which the remains 01 
 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 rep- 
 tiles, which are very abundant 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 Plesio- 
 saurus. The Pterodactyl also, a flying reptile, is met with in the same 
 strata, and many remains of Chelonians of the genera Trionyx 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 the Lepidos- 
 
 Fig. 308. 
 
 Lepidotus ManteM, Agass. Wealden. 
 Palate and teeth. Z>. Side view of teeth. 
 
 c. Scale. 
 
 tens, 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, Me- 
 lama, Paludina, Cyrena, Cyclas, Unio (see fig. 309), and others, which 
 inhabit rivers or lakes ; but one band has been found at Punfield, in Dor- 
 setshire, indicating a brackish state of the water, where the genera Corbula 
 (see fig. 310), Mytilus, and Ostrea occur; and in some places this bed 
 
CH. XVIILJ WEALDEK FOSSILS. 
 
 Fig. 309. 
 
 263 
 
 Fig. 310. 
 
 Corbula, alata, Fitton. Magnified. 
 
 In brackish-water beds of the Hastings 
 
 Sands, Pnnfield Bay. 
 
 TJnio Valdervtix, Mant 
 
 Isle of Wight and Dorsetshire ; in the lower beds 
 of the Hastings Sands. 
 
 becomes purely marine, the species being for the most part peculiar, but 
 several of them well-known Lower Greensand fossils, among which Am- 
 monites 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 sand- 
 stone (see fig. 311). 
 
 Fig. 811. 
 
 Underside of slab of sandstone about one yard in diameter. 
 Stammerham, Sussex. 
 
 Near the same place a reddish sandstone occurs in which are innu- 
 merable 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 appearances 
 
264 
 
 AREA OF THE WEALDEN. 
 
 [CH. XVIII 
 
 Fig. 312. 
 
 Sphenopteris (/racilis (Fitton), from the 
 
 Hastings Sands near Tunbridge Wells. 
 
 a. A portion of the same magnified. 
 
 have been remarked in other places in this formation.* In the sam 
 division also of the Wealden, at Cuck- 
 iield, is a bed of gravel or conglomer- 
 ate, consisting of water-worn pebbles of 
 quartz and jasper, with rolled bones of 
 reptiles. These must have been drifted 
 by a current, probably in water of no 
 great depth. 
 
 From such facts we may infer that, 
 notwithstanding the great thickness of 
 this division of the Wealden, the whole 
 of it was a deposit in water of a moder- 
 ate depth, and often extremely shallow. 
 This idea may seem startling at first, yet such would be the natural con- 
 sequence 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 deepened, if newly 
 deposited mud and sand should raise the bottom one foot. On the con- 
 trary, 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 northwest to 
 southeast, from Surrey and Hampshire 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 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 
 
 * Mantell, Geol. of S. E. of England, p. 244. 
 
 f Fitton, Geol. of Hastings, p. 58; who cites Lander's Travels. 
 
CH. XVIIL] LOWER CRETACEOUS AND WEALDEN FLORA. 265 
 
 species of shells, such as now inhabit Louisiana, has been upraised, and 
 made to occupy a wide geographical area, while a newer delta is form- 
 ing ;* 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 conti- 
 nent, 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 hydrographical 
 basin, from whence a great body of fresh water was poured into the sea, 
 precisely at a period when the neighboring area of the Wealden was 
 gradually going downwards 1000 feet or more perpendicularly. 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 freshwater and sedi- 
 ment ? In answer to this question, we are fairly entitled to suggest that the 
 neighboring land may have been stationary, or may even have undergone 
 a contemporaneous slow upheaval. There may have been an ascending 
 movement 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 unmoved, 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 through- 
 out a large part of Europe at the close of the Wealden period, and this 
 subsidence brought in the cretaceous 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 second- 
 ary, exclusive of the cretaceous, " the age of gymnogens ;" and the third, 
 comprising the cretaceous and tertiary, " the age of angiosperms."J He 
 considers the lower cretaceous flora as displaying a transitional character 
 from that of a secondary to that of a tertiary vegetation, Coniferce and 
 Cycadea (or Gymnogens) still flourished, as in the preceding oolitic and 
 
 * See above, p. 84 ; and Second Visit to the U. S. vol. ii. chap, xxxiv. 
 
 f See the Author's Annivers. Address, GeoL Soc. 1850, Quart. Geol. Journ. voL 
 > i. p. 52. 
 
 \ In this and subsequent remarks on fossil plants I shall often use Dr. Lind-* 
 ley's terms, as most familiar in this country ; but us tlio-e of M. A. Brouyniart are 
 
266 LOWER CKETACEOUS AND WEALDEN FLORA. [Cn. XVIIL 
 
 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 " pliiner-kalk" of Ger- 
 many, 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 dicotyledonous leaves,* 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 
 of 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 important bearing on some 
 popular theories, for until lately none of these Exogeus (a class now con- 
 stituting 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 ex- 
 isting, while it favored the predominance of reptile life, and a cryptogamic 
 and gymnospennous flora. The coexistence, therefore, of Dicotyledonous 
 Angiosperms in abundance with Cycads and Coniferse, and with a rich 
 reptilian fauna, comprising the Iguanodon, Megalosaurus, Hylaeosaurus, 
 Ichthyosaurus, Plesiosaurus, and Pterodactyl, in the Lower Cretaceous se- 
 ries, 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 Wealden, 
 and one which supplies a new link between it and the tertiary flora, I 
 may mention the Gyrogonites, or spore-vessels of the Cham, lately found 
 in the Hastings series of the Isle of Wight. 
 
 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. Cryptogarnous am- } 
 
 phigens, or cellular > Thallogens. Lichens, sea- weeds, fungi, 
 cryptogamic. J 
 
 2. Cryptogamous aero- Acrogens. Mosses, equisetums, ferns, lyco- 
 
 gens. podiums, Lepidodendroa 
 
 3. Dicotyledonous gym- Gymnogens. Conifers and Cycads. 
 
 nosperms. 
 
 4 Dicot. Angiosperms. Exogens. Composites, leguminosae, umbel- 
 
 liferse, cruciferse, heaths, &c, 
 All native European trees ex- 
 
 cept conifers. 
 6. Monocotyledons. Endogens. Palms, lilies, aloes, ruhes, grasses, 
 
 &c. 
 * Geol. Quart. Jour. vol. vii. part 2, Miscell. p. 111. 
 
CH.XIX."! INLAND CHALK-CLIFFS IN" NORMANDY. 
 
 CHAPTER XLX. 
 
 DENUDATION OF THE CHALK AND WEALDEN. 
 
 Physical geography of certain districts composed of Cretaceous and Wealdeu 
 strata Lines of inland chalk-cliffs on the Seine in Normandy Outstanding 
 Dillars 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 Rise and denudation of the strata gradual Ridges formed 
 by harder, valleys by softer beds At what periods the "Weald valley was de- 
 nuded "Why no alluvium, or wreck of the chalk, in the central district of the 
 Weald Land has most prevailed where denudation has been greatest Ele- 
 phant 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 ob- 
 serving 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 gradu- 
 ally from the sea. This opinion is confirmed by the occasional occurrence 
 of what appeared 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, 
 \v here the river Seine and its tributaries flow through deep winding val- 
 leys, hollowed out of chalk horizontally stratified. Thus, for example, 
 if we follow the Seine for a distance of about 30 miles from Andelys to 
 Elboeuf, 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), where the chalk appears at 
 
268 INLAND CHALK-CLIFFS IN NORMANDY. [Cn. XIX. 
 
 Fig. 313. 
 
 Section across Valley of Seine. 
 
 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 pinnacles 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 num- 
 ber 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 presents 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 its neighborhood, 
 namely, white chalk, having occasionally a crystalline texture like mar- 
 ble, 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 gen- 
 Fig. 314. 
 
 View of the Tete d'Homme, Andelys, seen from above. 
 
 erally in a state of slow decomposition, either exfoliating or being cov- 
 ered with white powder, like the chalk cliffs on the English coast ; and, 
 as in them, this superficial powder contains in some cases common salt. 
 
 Other cliffs are situated on the right bank of the Seine, opposite 
 Tournedos, between Andelys and Pont de 1'Arche, where the precipices 
 are from 50 to 80 feet high : several of their summits terminate in pin- 
 
Cn. XIX.] CLIFFS OF CHALK IX XORMANDY. 
 
 Fig. 315. 
 
 Side view of the Tete d'Homme. White chalk with flints. 
 
 nacles ; and one of them, in particular, is so completely detached 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 waves 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 semi- 
 circular form round an adjoining coomb, like those in Sicily before de- 
 scribed (p. 76). 
 
 If we then descend the river from Vatteville to a place called Senne- 
 ville, we meet with a singular needle about 50 feet high, perfectly iso- 
 lated on the escarpment of chalk on the right bank of the Seine (see fig. 
 248). Another conspicuous range of inland cliffs is situated about 12 
 
 Fig. 31& Fig. 317. 
 
 Chalk pinnacle at Senneville. 
 
 Eoches d'Orival, EltxeuC 
 
 miles below on the left bank of the Seine, beginning at Elbceuf, and 
 comprehending the Roches d'Orival (see fig. 317). Like those before 
 described, it has an irregular surface, often overhanging, and with beds 
 
270 
 
 CLIFFS OF CHALK IN NORMANDY. 
 
 [On. XIX. 
 
 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, with which it is united by a narrow ridge 
 about 40 feet lower than its summit (see fig. 318). Like the detached 
 
 Fig. SiS. 
 
 View of the Koche de Pignon, seen from the south. 
 
 rocks before mentioned at Senneville, Vatteville, and Andelys, it may be 
 compared to those needles of chalk which occur on the coast of Nor- 
 mandy* (see fig. 319), as well as in the Isle of Wight and in Purbeck. 
 
 Fig. 319. 
 
 Needle and Arch of Etretat, in the chalk cliffs of Normandy. 
 Height of Arch 100 feet (Passy.)t 
 
 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 Nor- 
 mandy may, no doubt, be the chief cause of this difference. But the 
 
 * An account of these cliffs was read by the author to the British Assoc. at 
 Glasgow, Sept. 1840. 
 
 f Seine-Inferieure, p. 14'2, and pi. 6, fig. 1. 
 
CH. XIX.] DENUDATION OF THE CHALK AND WEALDEJJT. 271 
 
 frequent absence of all signs of littoral denudation in the valley of the 
 Seine itself is a negative fact of a far more striking and perplexing char- 
 acter. The cliffs, after being almost continuous for miles, are then wholly 
 wanting for much greater distances, 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 under- 
 mining force of the waves and marine currents varies greatly at different 
 parts of every coast ; secondly, that precipitous rocks have often decom- 
 posed and crumbled down ; and thirdly, that terraces and small cliffs 
 may occasionally lie concealed beneath a talus of detrital matter. 
 
 Denudation of the Weald Valley. No district is better fitted to illus- 
 trate the manner in which a great series of strata may have been up- 
 heaved and gradually denuded than the country intervening between 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 inclusive, 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 ap- 
 pear at the surface. The whole of this district may therefore be consid- 
 ered geologically as one and the same. 
 
 Fig. 320. 
 
 .Estuary ofTIiames 
 
 Geological map of the southeast of England and part of France, exhibiting the denudation 
 of the Weald. 
 
 1. H~""n Tertiary. 
 
 - ^ J Chalk and upper greensand. 
 
 3. MM Gault. 
 
 4. fc^H Lower Greensand. 
 
 Weald clay. 
 Hastings sands. 
 
272 DENUDATION OF THE CHALK AND WEALDEN. [On. XIX. 
 
 The space here inclosed within the escarpment of the chalk affords an 
 example of what has been sometimes called a " valley of elevation" 
 (more properly " of denudation") ; where the strata, partially removed by 
 aqueous excavation, dip away on all sides from a central axis. Thus, it 
 
 if 
 
 S J 
 
 1 1 
 
 t 
 
 , i 
 
 a 
 
 
 O .j 
 CO <J> 
 
 GO o 
 
 - 
 
 ; i 
 
 
 CO 
 
 S cT 
 11 
 
 i 
 
CH. XIX.] TKAXSVERSE VALLEYS. . 273 
 
 is supposed, that the area now occupied by the 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, tHt 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 exhibited 
 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 comparison 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 de- 
 nuded 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 in- 
 troduced, as in the diagrams of Smith, Mantell, Conybeare, and others, 
 geologists have always been well aware that 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 undergone the 
 greatest displacement ; one fault being known, where the vertical shift of 
 a bed of calcareous grit is no less than 60 fathoms.* Much of the pic- 
 turesque 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.f If these transverse 
 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 Rornney Marsh and Pevensey Levels. J 
 
 * Fitton, Geol. of- Hasting?, p. 55. f Conybeare, Outlines of GeoL p. 81. 
 
 18 
 
274: 
 
 CHALK ESCARPMENTS. 
 
 [On. XIX. 
 
 Mr. Martin has suggested that the great cross fractures of the chalk, 
 which have become 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, seemed to coincide in direction ; and in 
 
 like manner, the Ouse corre- 
 sponds to the Darent, and the 
 Cuckmere to the Medway.* 
 
 Although these coincidences 
 may, perhaps, be accidental, it 
 is by no means improbable, as 
 hinted by the author above 
 mentioned, that great amount 
 of elevation towards the centre 
 of the Weald district gave rise 
 to transverse fissures. And as 
 the longitudinal valleys were 
 connected with that linear move- 
 ment which caused the anti- 
 clinal lines running east and 
 west, so the cross fissures migh 
 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 
 movement may have acted, 7 
 shall endeavor to make the 
 reader more intimately acquaint- 
 ed with the leading geographi- 
 cal features of the district, so 
 far as they are of geological in- 
 terest. 
 
 In whatever direction we travel 
 from the tertiary strata of the 
 basins of London and Hamp- 
 shire towards the valley of the 
 Weald, we first ascend a slope 
 of white chalk, with flints, and 
 then find ourselves on the sum- 
 mit of a declivity consisting, for 
 the most part, of different mem- 
 bers of the chalk formation ; 
 below which the upper green- 
 
 * Geol. of Western Sussex, p. 61. 
 
CH. XIX.] 
 
 TRANSVERSE VALLEYS. 
 
 275 
 
 sand, 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 (Xo. 3). The escarpment is continuous along the southern ter- 
 mination of the North Downs, and may be traced from the sea, at 
 Folkestone, westward to Guildford and the neighborhood 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. 274), part of the escarpment of the South 
 Downs is faithfully represented, where the denudation at the base of 
 the declivity has been somewhat more extensive than usual, in conse- 
 quence of the upper and lower greensand being formed of very inco- 
 herent materials, the former, indeed, being extremely thin and almost 
 wanting. 
 
 The geologist cannot fail to recognize 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 see the same line 
 
 Fig. 324. 
 
 Chalk escarpment, as seen from the hill above Steyning, Snssex. The castle and village 
 of Bramber in the foreground. 
 
 of heights prolonged. Even those who are not accustomed to specu- 
 late 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 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 sur- 
 face far from the summit of an escarpment, whenever portions of the 
 chalk are cut away. 
 
 In regard to the transverse valleys before mentioned, as intersecting 
 the chalk hills, some idea of them may be derived from the subjoined 
 
276 
 
 TKANSVERSE VALLEYS. 
 
 XIX, 
 
 [ \ 
 
 JV: 
 
 i 
 
 sketch (fig. 325) of the gorge of the River Adur, taken from the sum- 
 mit 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. 274), he 
 will there see the exact point where the gorge of which I am now 
 speaking interrupts 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 evi- 
 dent that these openings could 
 not have been produced by rivers, 
 except under conditions of physi- 
 cal geography entirely different 
 from those now prevailing. In- 
 deed, 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. 
 
 That the place of some, if not 
 of all, the gorges running north 
 and south, has been originally de- 
 termined by the fracture and dis- 
 placement 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 undoubt- 
 edly due to dislocation. This ra- 
 vine is called " the Coomb" (fig. 
 326), and is situated in the sub- 
 urbs of the town of Lewes. It 
 was first traced out by Dr. Man- 
 tell, in whose company I exam- 
 ined it. The steep declivities on 
 each side are covered with green 
 turf, as is the bottom, which is 
 perfectly dry. No outward signs 
 of disturbance are visible ; and 
 the connection of the hollow with 
 subterranean movements would 
 
C*. XIX.] 
 
 COOMB NEAR LEWES. 
 
 277 
 
 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 
 
 Fig; 826. 
 
 The Coomb, near Lewes. 
 
 Ouse, and the numerous chalk-pits worked at the termination of the 
 Coomb. By the aid of these we discover that the ravine coincides pre- 
 cisely with a line of fault, on one side of which the chalk with flints (a, 
 fig. 327) appears at the summit of the hill, while it is thrown down to 
 the bottom on the other. 
 
 Fig. 327. 
 
 Fault coinciding with the Coomb, in the Cliff-hill near Lewes. ManteU. 
 a. Chalk with flints. 5. Lower chalk. 
 
 In order to account for the manner in which the five groups of 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 hypoth- 
 esis 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.* 
 
 * See illustrations of this theory, by Dr. Fitton, Geol. Sketch of Hastings. 
 
278 PROMINENCE OF HARDER STRATA. [Cn. XIX. 
 
 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 slowly 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 ex- 
 ample, the chalk with flints, together with the subjacent upper green- 
 sand, 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, exca- 
 vated chiefly out of the soft argillaceous bed, termed gault (No. 3. 
 map, p. 272). 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 quar 
 ter of a mile to three miles, and following the sinuosities of the . chalk 
 escarpment.* 
 
 Fig. 828. 
 
 a. Chalk with flints. 5. Chalk without flints. 
 
 c. Upper greensand, or firestone. d. Gault. 
 
 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 up- 
 heaval of a coast preyed upon by the waves. During the inter- 
 
 * Sir R. Murchison, Geol. Sketch of Sussex, <fec , Geol. Trans., Second Series, 
 vol. ii. p. 93. 
 
CH. XIX.] DENUDATION OF THE WEALD. 279 
 
 val 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 out- 
 crop 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 areensand : but as the upper beds of this last formation 
 
 O JT A 
 
 are most commonly loose and incoherent, they also have usually 
 disappeared and increased the breadth of the valley. In those dis- 
 tricts, however, where chert, limestone, and other solid materials en- 
 ter largely into the composition of this formation (No. 4, map, p. 
 272), 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 figure 321. 
 p. 272), which usually forms a broad valley, separating the lower 
 greensand from the Hastings sands or Forest Ridge ; but where sub- 
 ordinate beds of sandstone of a firmer texture occur, the uniformity 
 of the plain of No. 5 is broken by waving irregularities and hil- 
 locks. 
 
 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 calca- 
 reous matter, of a milk-white color, 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 undermined, 
 and cavities may be formed or enlarged, even by that part of the drain- 
 age which is subterranean.* 
 
 * See above, p. 82, 83, " Sand-pipes in Chalk ;" and Prestwich, Geol. Quart, 
 Journ. voL x. p. 222. 
 
280 THEORY OE FRACTURE AND UPHEAVAL. [Ca XIX. 
 
 Lines of Fracture. Mr. Martin, in his work on the g'eology of West- 
 ern Sussex, published in 1828, threw much light on the structure of 
 the Wealden by tracing out continuously for miles the direction of 
 many anticlinal lines and cross fractures ; and the same course of investi- 
 gation 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 theo- 
 retically on mechanical principles, if we assume certain simple conditions 
 under which the strata were lifted up by an expansive subterranean 
 force.* 
 
 His opinion, that both the longitudinal and transverse lines of frac- 
 ture 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.f For the accuracy of the map 
 and sections of the Swiss geologist I can vouch, from personal exami- 
 nation, in 1835, of part of the region surveyed by him. Among other 
 results, at which he arrived, it appears that the breadth of the anticli- 
 nal ridges and dome-shaped masses in the Jura is invariably great ir. 
 proportion to the number of the formations exposed to view; or, in 
 other words, to the depth to which the superimposed groups of sec- 
 ondary 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 fractures are imagined by 
 him to have been contemporaneous with others subsequent to the lon- 
 gitudinal 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 southeast 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 JStna were 
 poured out many thousands, perhaps myriads of years before the 
 newest, and yet they, and the movements accompanying their emis- 
 sion, 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, 
 may, by reiterated movements, produce the most perfect unity of 
 result ? 
 
 * Geol Soc. Proceed. No. 74, p. 363, 1841, and G. S. Trans. 2 Ser. vol. 7. 
 f Soul^vemens Jurassiques. 1832. 
 
CH. XIX.] PERIODS OF DENUDATION IN THE WEALD. 281 
 
 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 numinulitic rocks of Europe and Asia were 
 formed. The date, therefore, of part of the changes now under contem- 
 plation 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 probably 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 supposed, 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 contem- 
 poraneous strataf 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, 6, 
 were deposited. Some small patches of the last-mentioned beds, &', 
 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. Ge"ol. de France, vol. i. part i. p. Ill, pL 7, fig. 5. 
 f See p. 220, above. 
 
282 ISLANDS IN THE EOCENE SEA. [On. XIX 
 
 Fig. 329. 
 
 G 
 
 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, &'. 
 a. London Clay. &, 6'. 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, 5, &', were formed. 
 In other words, the central parts of the Wealden, south of x, 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 extended 
 
 Fig. 830. 
 
 Island in the Eocene Sea. 
 a. Chalk, Upper Greensand, and Gault. Z>. Lower Greensand. 
 
 c. "Wealden. 
 
 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 denudation since the commence- 
 ment 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 Creta- 
 ceous Ocean, so as to check the accumulation 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 
 
CH. XIX.] WEALD, WHEN DENUDED. 283 
 
 so near, the white 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 ex- 
 clusively 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 cretaceous series. 
 
 But, although we must assume that the white chalk was once contin- 
 uous, 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. 238, 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 depo- 
 sition 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 innu- 
 merable phases in physical geography through which the southeast 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 con- 
 formation 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 move- 
 ments 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 freshwater beds of Woolwich and other Lower Eocene 
 deposits were depressed (see above, p. 221) 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 area of the Weald could scarcely fail to 
 
284 AT WHAT PERIODS [On. XIX. 
 
 share in the movement, and some parts at least of the island before 
 spoken of (fig. 330, p. 282) 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 corresponding age in the 
 south, or in the Hampshire basin ; because none of the fluvio-marine 
 Eocene strata of Hordwell and th 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 freshwater 
 beds of Hampshire, of Middle and Upper Eocene date, bear testimony to 
 rivers draining adjacent lands, and to the existence of numerous quadru- 
 peds 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 southeast 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 
 frequently, 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 (or falunian) 
 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 sug- 
 gested (p. 180). Hence we are entitled to speculate on the probability 
 of revolutions in the physical geography of the Weald in times inter- 
 mediate 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 be- 
 ginning 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 opera 
 ting in Sweden and in Greenland. 
 
CH. XIX.] THE WEALD VALLEY WAS DENUDED. 285 
 
 Lastly. The reader must recall to mind what was said in the llth and 
 12th chapters, of the glacial drift and its far-transported materials. 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 com- 
 monly 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, pp. 136 and 153) 
 flourished, and when the elephant, rhinoceros, hippopotamus, extinct 
 beaver, and other mammals peopled that country. It may also be pre- 
 sumed 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 England and 
 parts of Europe may have undergone, after the commencement 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 reconverted into land at a time when 
 England was united to the continent, 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 de- 
 pend, would lead me into too long a digression ; I merely allude to 
 them in this place to show that, while the researches of Mr. Prest- 
 wich establish the extreme remoteness of the period when the de- 
 nuding 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 de- 
 monstrated that strata of chalk with flints, nearly as thick as the white 
 chalk of the Isle of Wight and Purbeck, have undergone disturbances 
 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 bendings and foldings 
 of the older beds, and have evidently suffered the same derangement. 
 If, therefore, we find it necessary, in order to explain the position 
 
 * Geol. Quart. Journ. voL ix. pi. 13. 
 
 J- Puggaard, Moens Geologic, 8vo. : Copenhagen, 1851. 
 
286 WEALD, HOW DENUDED. [Cn. XIX. 
 
 of some beds of gravel, loam, or drift in the southeast of Bug-land, to im- 
 agine important dislocations of the chalk and local changes of leyel since 
 the Glacial period, such speculations are in harmony with conclusions 
 derived from independent sources, or drawn from the exploration of for- 
 eign 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 im- 
 mediately 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. 273), 
 if the chalk (No. 2) were once continuous and covered everywhere 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 thickness of the groups removed in succession, is the prob- 
 ability 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 gen- 
 eral 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 indicated in the annexed section 
 (fig. 331). Even here it will be seen that the gravel reaches no farther 
 
 Fig. 331. 
 
 Barcoinle 
 
 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 Avith and without flints. 
 
 3. Lowest chalk or chalk-marl (upper greensand wanting). 
 
 4. Gau'.t 5. Lower greensand. 6. Weald clay. 
 
 than the Weald clay. But 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. 272) 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 often put, how 
 
CH. XIX.] 
 
 ELEPHANT- BED . 
 
 287 
 
 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 attrition ; first, where the gravel 
 was spread originally over the Eocene deposits ; and, secondly, after 
 the Eocene sands and clays were undermined and the modern cliff 
 formed. 
 
 Angular flint-breccia is not confined to the Weald, nor to the trans- 
 verse gorges in the chalk, but extends along the neighboring 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. 832. 
 
 A. Chalk -with layers of flint dipping slightly to the south. 
 
 &. Ancient beach, consisting of fine sand, from one to four feet thick, covered by shingle from 
 
 five 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. 
 & Sand and shingle of modern beach. 
 
 * See also Sir R. Murchison, GeoL Quart. Journ. voL vii. p. 365. 
 
288 SANGATTE CLIFF. [Cn. XIX. 
 
 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 littorea and 
 other recent littoral shells determines the modern date of the accumu- 
 lation. 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 re- 
 cently 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 tach, with an incum- 
 bent 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 in- 
 land, 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 com- 
 ponent 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 accumu- 
 lated. 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. Prestwich 
 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 stratification, 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 abun- 
 dance 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 forma- 
 tions* of glacial origin ought not to excite surprise. As to the angulariJty 
 
CIL XIX.] DENUDATION OF THE WEALD. 289 
 
 of the flints, it has been thought by some authorities to imply great vio- 
 lence 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, there- 
 fore, we do or do not admit the occurrence of reiterated 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 un'der 
 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 atmo- 
 sphere, land-floods, and rivers (some of them larger than those now 
 flowing in the same valleys) may have modified the surface and ob- 
 literated 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 re- 
 moval 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 up- 
 heaval and subsidence and dislocation of rocks which all admit to have 
 taken place. 
 
 In despair of solving the problem of the present geographical config- 
 uration and geological structure of the Weald by an appeal to ordinary 
 causation, some geologists 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 subter- 
 ranean reservoirs, when the rocks were riven by earthquake-shocks of in- 
 tense violence. The singleness of the cause and the unity of the result 
 are emphatically insisted upon : the catastrophe was abrupt, tumultuous, 
 transient, and paroxysmal ; fragments of stone were swept along to great 
 
 19 
 
290 CONCLUSION. [Cn. XIX 
 
 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 endeavored to show how numerous have been the periods 
 of geographical change, and how vast their duration. Evidence to this 
 effect is afforded by the relative position of the chalk and overlying ter- 
 tiary 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 denuda- 
 tion on a grand scale, always effected slowly ; for each superimposed 
 stratum, however thin, has been successively 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 gratuitous rejection of the only kind of machinery known to 
 us which possesses the adequate power. j;:^;: :. 
 
 If, then, at every epoch, from the Cambrian to the Pliocene inclusive, 
 voluminous masses of matter, such as are missing in the Weald, have 
 been transferred from place to place, and always removed gradually, 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 anywhere within the 
 range of geological inquiry, we have time enough and without stint at 
 our command. 
 
OH. XX.] DIVISIONS OF THE OOLITE. 291 
 
 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 Pur- 
 beck 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 N"erinaean limestone 
 Diceras limestone Oxford clay, Ammonites and Belemnites Lower Oolite, 
 Crinoideans Great Oolite and Bradford clay Stonesfield slate Fossil mam- 
 malia, placental and marsupial Kesemblance to an Australian fauna North- 
 amptonshire 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 Purbeck 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 ex- 
 amined, the limestones belonging to it had an oolitic structure (see p. 12). 
 These rocks occupy in England a zone which is nearly 30 miles in aver- 
 age breadth, and extends across the island, from Yorkshire in the north- 
 east, to Dorsetshire in the southwest. Their mineral characters are not 
 uniform throughout this region ; but the following are the names of the 
 principal subdivisions observed in the central and southeastern parts of 
 England : 
 
 OOLITE. 
 
 ( a. Purbeck beds. 
 
 Upper < b. Portland stone and sand. 
 ^ c. Kimmeridge clay. 
 
 \fAA-t < <i Coral ra. 
 Mlddle U Oxford clay 
 
 {/. Cornbrash and Forest marble. 
 g. Great Oolite and Stonesfield slate. 
 h. Fuller's earth. 
 i. Inferior Oolite. 
 
 The Lias then succeeds to the Inferior Oolite. 
 
292 PHYSICAL GEOGRAPHY OF THE OOLITE. [Co. XX 
 
 The Upper oolitic system of the above table has usually the Kimme- 
 ridge 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 subdivisions are distinguished by pe- 
 culiar 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 northeast 
 of France and the Jura mountains adjoining. In that country, distant 
 above 400 geographical miles, the analogy to the accepted English type, 
 notwithstanding the thinness or occasional absence of the clays, is more 
 perfect than in Yorkshire or Normandy. 
 
 Physical geography. The alternation, on a grand scale, of distinct for- 
 mations 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 Eng- 
 land and France. Wide valleys can usually be traced throughout the 
 long bands of country where the argillaceous strata crop out ; and be- 
 tween 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, in this drawing, greatly 
 
 Fig. 833. 
 
 Lower Middle Upper London 
 
 Oolite. Oolite. Oolite. Chalk, clay. 
 
 Lias. Oxford Clay. Kim. clay. Gault. 
 
 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, 
 Kimmeridge clay, Oxford clay, and Lias. This last forms, generally, a 
 broad vale at the foot of the escarpment of inferior oolite, but where it 
 acquires 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. 
 
CH. XX.] 
 
 UPPER PURBECK. 
 
 293 
 
 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 inter- 
 vening 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 similarly 
 over an area several hundred miles in diameter, sweeping away the softer 
 clays more extensively than the limestones, and undermining 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. 291). 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 reference to the history 
 of a vast lapse of ages. The Purbeck beds are finely exposed to view in 
 Durdlestone Bay, near Swanage, Dorsetshire, and at Lulworth Cove and 
 the neighboring bays between Weymouth and Swanage. At Meup's 
 Bay, in particular, Professor K 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 ap- 
 pears from these researches that the Upper, Middle, and Lower Purbecks 
 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 fresh- 
 water, 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, 6, c.) 
 
 Fig. 334, 
 
 Cyprides from the Upper Purbecks. 
 a. Cypris gittoafiiE. Forbes. &. Cypris tuberculala, HForbes. c. Cypris legumintOa, RForbei, 
 
 * "On the Dorsetshire Purbecks," by Prof. E. Forbes, Brit Assoc. Ediab. 1850. 
 
294 
 
 MIDDLE PURBECK. 
 
 [On. XX. 
 
 The stone called " Purbeck marble," formerly much used in ornamental 
 architecture in the old English cathedrals of the southern counties, is ex- 
 clusively procured from this dirision. 
 
 Middle Purbeck. Next in succession is the Middle Purbeck, about 30 
 feet thick, the uppermost part of which consists of freshwater limestone, 
 with cyprides, turtles, and fish, of different species from those in the pre- 
 ceding strata. Below the limestone are brackish-water beds full of 
 Cyrena, and traversed by bands abounding in Corbula and Melania. 
 These are based on a purely marine deposit, with Pecten, Modiola, 
 Avicula, Thracia, all undescribed shells. Below this, again, come lime- 
 stones 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 
 mollusks, a remarkable ribbed Melania, of the section Chilina, 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 Professor Forbes discovered the first echino- 
 denn (fig. 336) as yet known in the Purbeck series, a species of Hemici- 
 daris, a genus characteristic of the Oolitic period, and scarcely, if at all, 
 distinguishable from a previously known oolitic species. It was accom- 
 
 Fig. 335. 
 
 Fig. 836. 
 
 Ostrea distorta. 
 Cinder-bed, Middle Purbeck. 
 
 Hemioidaris Purbecfcensis. E. Forbes. 
 Middle Purbeck. 
 
 panied by a species of Perna. Below the Cinder-bed freshwater strata 
 are again seen, filled in many places with species of Cypris (fig. 337, 
 
 Cyprides from the Middle Purbecks. 
 
 a. Cypris striato-punctata, E. Forbes. 6. Cypris fasciculata, E. Forbes. 
 c. Cypris granulata, Sow. 
 
 a, b, c), and with Valvata, Paludina, Planorbis, Limnceus, Physa 
 (fig. 338), and Cydas, all different from any occurring higher in the 
 
CH. XX.] FOSSILS OF THE MIDDLE PUKBECK. 295 
 
 series. It will be seen that 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 places far from the Dorsetshire cliffs, as, for example, in 
 the Vale of Wardour, in Wiltshire. Thick siliceous beds Purbeck. 
 of chert occur in the Middle Purbeck filled with mollusca and cyprides ot 
 the genera already enumerated, in a beautiful state of preservation, often 
 converted into chalcedony. Among these Professor Forbes met with 
 gyrogonites (the spore-vessels of Charce), plants never until 1851 discov- 
 ered in rocks older than Eocene. In a bed of this series, about 20 feet 
 below the " Cinder," Mr. W. K. Brodie has lately foond (1854), in Dur- 
 dlestone Bay, portions of several small jaws with teeth, which Professor 
 Owen, after clearing away the matrix, recognized as belonging to a small 
 mammifer of the insectivorous class. The teeth with pointed cusps re- 
 semble 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 Thylacotherium of the Stones- 
 field Oolite (see below, Chap. XX.). This newly-found quadruped, there- 
 fore, seems to have been more closely allied in its dentition to the 
 Thylacotherium than to any existing insectivorous type. As in Thylaco- 
 therium, the angular process of the jaw is not bent inwards, an osteologi- 
 cal peculiarity confined to the marsupial tribes (see Chap. XX.), and 
 Professor Owen therefore refers the Spalatotherium 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 re- 
 marked that, although no mammalia had then been found, " it was too 
 soon to infer their non-existence on mere negative 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 Ter- 
 tiary 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 fluviatile strata, and our 
 total ignorance of the deposits formed in lakes and caverns at the same 
 date, it would be premature to attempt to generalize on the nature of so 
 ancient a terrestrial fauna. 
 
296 
 
 LOWER PUEBECK. 
 
 [On. XX 
 
 Fig. 839. 
 
 Beneath the freshwater strata last described, a very thin band o. 
 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 mentioned, 
 purely freshwater marls occur, containing species of Cypris (fig. 339, 
 a, 5), Valvata, and Lymnceus, dif- 
 ferent from those of the Middle 
 Purbeck. This is the beginning a, 
 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 Cyprldes from the Lower Purbecks. 
 
 Serpula, allied to, if not identical a. Cypris Purleckensis, &. Cypris punctata, 
 
 with, Serpula coacervites, found in 
 
 beds of the same age in Hanover. There are also shells of the genus 
 Rissoa (of the subgenus Hydroibia), and a little Cardium of the sub 
 genus 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 enumerated 
 in the above list, is that called by 
 the quarrymen "the dirt," or 
 " black dirt," which was evidently 
 an ancient vegetable soil. It is 
 from 12 to 18 inches thick, is of 
 a dark brown or black color, and 
 contains a large proportion of 
 earthy lignite. Through it are 
 dispersed rounded fragments of 
 stone, from 3 to 9 inches in diame- 
 ter, in such numbers that it almost 
 deserves the name of gravel. Many 
 silicified trunks of coniferous trees, and the remains 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). 
 
 * Weston, Geol. Q. J., vol. viii. p. 117. 
 
 Fig. 840. 
 
 Cycadeoidea (Mantellia) megalophylla, 
 Buckland. 
 
CH. XX.] FOSSIL FOREST IN ISLE OF PORTLAND. 297 
 
 Fig. 341. 
 
 Zamia epiralis. 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 Cycadece.\ 
 
 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. 842. 
 
 freshwater calcareous slate. 
 
 dirt-bed and ancient forest 
 
 lowest freshwater beds of the Lower 
 Purbeck. 
 
 Portland stone, marine. 
 Section in Isle of Portland, Dorset (Bnckland 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. Pro- 
 fessor Forbes has ascertained that the subjacent rock is a freshwater limestone, 
 and not a portion of the Portland oolite, as was previously imagined. 
 
298 
 
 FOSSIL FOREST IN LULWORTH COVE. 
 
 [On. XX. 
 
 The thin layers of calcareous slate (fig. 342) were evidently deposited 
 tranquilly, and would have been horizontal but for the protrusion of the 
 stumps of the trees, around the top of each of which they form hemispher- 
 ical 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 hori- 
 zontal (see fig. 343). Traces of the dirt-bed have also been observed by 
 
 Fig. 843. 
 
 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.) 
 
 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 cov- 
 ered 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 sub- 
 merged with its forests beneath a body of freshwater, from which sedi- 
 ment was thrown down enveloping fluviatile shells. 3dly. The regular 
 and uniform preservation of this thin bed of black earth over a distance 
 of many miles, shows that the change from dry land to the state of a 
 freshwater lake or estuary, was not accompanied by any violent denuda- 
 tion, 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 
 bad 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 
 -Cycadew, in an upright position, have been found below it, and one 
 
CH. XX.] 
 
 CHANGES OF MEDIUM. PURBECK BEDS. 
 
 299 
 
 above it, which implies other oscillations in the level of the same ground, 
 and its alternate occupation by land and water more than once. 
 
 m 
 
 Table showing the changes of medium in which the strata were formed, 
 from the Portland Stone up to the Lower Greensand inclusive, in the 
 southeast of England (beginning with the lowest). 
 
 Portland Stone. 
 
 Lower Purbeck. 
 
 3. Marine 
 
 
 . Freshwater 
 
 
 Marine 
 
 
 Brackish 
 
 Middle Purbeck 
 
 Marine 
 
 
 Brackish 
 
 
 Freshwater 
 
 
 4. Freshwater Upper Purbeck. 
 
 6. Freshwater ) 
 
 Brackish > Hastings Sands. 
 
 Freshwater j 
 
 6. Freshwater Wealden Clay. 
 
 7. Marine Lower Greensand. 
 
 1. Marine 
 
 2. Freshwater 
 Land 
 
 Freshwater 
 Land 
 
 Freshwater 
 Land (Dirt-bed) 
 Freshwater 
 Land 
 Brackish 
 Freshwater 
 
 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 Eng- 
 land 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 sufficient 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 his- 
 tory 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 Cutch,f where land has been laid 
 permanently 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 disturbance, 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-bed, do not indicate any breaks in the 
 
 See Principles of Geol. 9th ed. pp. 255-275. 
 
 f Ibid. p. 460 
 
300 PORTLAND STONE. [On. XX. 
 
 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 repre- 
 sent as many ages, we need not expect on that account to find them 
 constituting the lines of separation between successive strata character- 
 ized by different zoological types. The preservation of a layer of vege- 
 table 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, Coniferas (fig. 344), and Cycadese (fig. 
 340), without any exogens; the whole more allied 
 to the Oolitic than to the Cretaceous vegetation. Fig.844 
 
 The vertebrate and invertebrate animals indicate, 
 like the plants, a somewhat nearer relationship 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 plants, while others are 
 of such forms as hover over the surface of our present 
 
 Cone of a pine from the 
 rivers. Isle of p urbock (Fitton). 
 
 Portland Stone and Sand (b, Tab. p. 291). The 
 
 Portland stone has already been mentioned as forming in Dorsetshire the 
 foundation on which the freshwater limestone of the Lower Purbeck re- 
 poses (see p. 296). 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 
 almost wholly confined to the southern counties. Corals are rare in 
 them, although one species is found plentifully at Tisbury, Wiltshire, in 
 the Portland sand, converted into flint and chert, the original 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 bituminous 
 
CH. XX.] FOSSILS OF THE PORTLAND STONE. 301 
 
 Fig. 345. 
 
 Fig. 846. 
 
 Isastrcea oblong a, M. Edw. and J. Haime. 
 
 As seen on a polished slab of chert from 
 
 the Portland sand, Tisbury. 
 
 Fig. 347. 
 
 Trigonia gibbosa. J nat size. 
 
 a, the hinge. 
 Portland Stone, Tisbury. 
 
 Fig. 343. 
 
 Cardium dissimile. nat size. 
 Portland Stone. 
 
 Ostrea e&pansa. 
 Portland Sand. 
 
 matter may have been, in part at least, derived from the decomposition 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 striatu- 
 lum (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), also met with 
 
 Fig. 349. 
 
 Fig. 850. 
 
 Fig.861. 
 
 Cardium stHatulum. 
 Kimmeridge clay, Hartwell. 
 
 Ostrea dettoidea. GryphoM virgula. 
 
 Upper Oolite : Kimmeridge clay, i nat size. 
 
 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 Clennont, in Argonne, a few leagues from St. 
 Menehould, where these indurated marls crop out from beneath the Gault, 
 
302 
 
 CORAL RAG. 
 
 [Cn. XX. 
 
 Fig. 352. 
 
 Trigonellites latus. 
 Kimmeridge clay. 
 
 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 spe- 
 cies 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 calca- 
 reous plates. 
 
 The celebrated lithographic stone of Solenhofen, in Bavaria, belongs 
 to one of the upper divisions of the oolite, and affords a remarkable ex- 
 ample of the variety of fossils which may be preserved under favorable 
 circumstances, and what delicate impressions of the tender parts of cer- 
 tain 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 spe- 
 cies 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 Skeleton of Pterodactyl 
 
 . ,-L * crass^rostns. 
 
 lizards, and other contemporaneous reptiles, re- Oolite of Pappcnheim, near So- 
 
 lenhofen. 
 
 sorted. 
 
 Fig. 363. 
 
 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 Tham- 
 nastrcea (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 1ST. W. of Berkshire, and north of Wilts, and 
 
CH. XX.] 
 
 Fig. 854. 
 
 CORALS OF THE OOLITE. 
 Corals of the Coral Bag. 
 
 303 
 
 Fig. 855. 
 
 Thecosmilia anmtlaris, Milne Edw. and J. Haime. 
 Coral rag, Steeple Ashton. 
 
 Thamnastrcea. 
 Coral rag, Steeple Ashton. 
 
 again recur inYorkshire, 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 Nerinees) 
 by M. Thirria ; Nerincea being an extinct genus of univalve shells, much 
 resembling the Cerithium in external form. The annexed 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. 857. 
 
 Fig. 358. 
 
 Fig. 
 
 Ostrea gregarea. 
 Coral rag, Steeple Ashton. 
 
 Nerincea hieroglyphica. 
 Coral rag. 
 
 Nerincea Goodhallii, Fitton. 
 Coral rag, Weymouth. nat size. 
 
 (fig. 358) is another English species of the same genus, from a formation 
 which seems to form a passage from the Kimmeridge clay to the coral 
 rag.* 
 
 A division of the oolite in the Alps, regarded by most geologists as 
 coeval with the English coral rag, has been often named " Calcaire a Di- 
 cerates," 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, vol. iv. pi. 23, fig. 12. 
 
304: 
 
 FOSSILS OF OXFOKD CLAY. 
 
 Fig. 860. 
 
 <m 
 
 Fig 859. 
 
 [Cn. XX, 
 
 Cast of Diceras arietina. 
 Coral rag, France. 
 
 Cidaris coronata. 
 Coral rag. 
 
 Oxford Clay. The coralline limestone, or " coral rag," above de- 
 scribed, and the accompanying sandy beds, called " calcareous grits" of 
 the Middle Oolite, rests 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. 
 (Figs. 361, 362.) In some of the clay of very fine texture ammonites are 
 
 Fig. 861. 
 
 Belemnites hastatus. Oxford Clay. 
 
 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 discovered in the cuttings of the Great "Western 
 Railway, near Chippenham, in 1841, and have been described by Mr. 
 Pratt.* 
 
 Fig. 3C2. 
 
 Ammonites Jason, Eeinecke. Syn. A. Elizabeths, Pratt. 
 Oxford clay, Christian Malford, Wiltshire. 
 
 S. P. Pratt, Annals of Nat. Hist. November, 1841. 
 
On. XX.] 
 Fig. 
 
 LOWER OOLITE. 
 
 305 
 
 Bdemnites Puzosianus, 
 
 D'Orb. 
 Oxford Clay, Christian 
 
 Malford. 
 
 a, a. Projecting processes of 
 the shell or phragmo- 
 cone. 
 
 Z>, c. Broken exterior of a 
 conical shell called 
 the phragmoconc, 
 which is chambered 
 within, or composed 
 of a series of shallow 
 concave shells pierced 
 by a siph ancle. 
 o, <?. The guard or osselet, 
 which is commonly 
 called the belemnite. 
 
 Similar elongated processes have been also ob 
 served to extend from the shells of some belem- 
 nites discovered by Dr. Mantell in the same clay 
 (see fig. 363), \vho, by the aid of this and other 
 specimens, has been able to throw much light on 
 the structure of this singular extinct form of 
 cuttle-fish.* 
 
 LOWER OOLITE. 
 
 Cornbrash and Forest Marble. The upper 
 division of this series, which is more exten- 
 sive than the preceding or Middle Oolite, 
 is called in England the Cornbrash. It con- 
 sists of clays and calcareous sandstones, which 
 pass downwards into the Forest Marble, an 
 argillaceous limestone, abc:inding in marine 
 fossils. In some places, as at Bradford, this 
 limestone is replaced by a mass of clay. The 
 sandstones of the Forest Marble of "Wiltshire are 
 often ripple-marked and filled with fragments of 
 broken shells and pieces of drift-wood, having 
 evidently been formed on a coast. Rippled slabs 
 of fissile oolite are used for roofing, and have 
 been traced over a broad band of country from 
 Bradford, in Wilts, to Tetbury, in Gloucestershire. 
 These calcareous tile-stones are separated from 
 each other by thin seams of clay, which have 
 been deposited upon them, and have taken their 
 form, preserving the undulating ridges and fur- 
 rows of the sand in such complete integrity, that 
 the impressions of small footsteps, apparently of 
 crabs, which walked over the soft wet sands, are 
 still visible. In the same stone the claws of 
 crabs, fragments of echini, and other signs of a 
 neighboring beach are observed.f 
 
 Great Oolite. Although the name of coral- 
 rag has been appropriated, as we have seen, to a 
 member of the Upper Oolite before described, 
 some portions of the Lower Oolite are equally 
 entitled in many places to be called coralline 
 limestones. Thus the Great Oolite near Bath 
 contains various corals, among which the Euno- 
 mia radiata (fig. 364 is very conspicuous, single 
 individuals forming masses several feet in diam- 
 
 See Phil. Trans. 1850, p. 393. 
 P. Scrope, Geol. Proceed. March, 1831. 
 20 
 
306 
 
 BRADFORD ENCRINITES. 
 Fig. 364. 
 
 [C H . XX, 
 
 Eunomia radiata, Lamouroux. (Calamophyttia, Milne Edw.) 
 
 a. Section transverse to the tubes. 
 
 b. Vertical section, showing the radiation of the tubes. 
 
 c. Portion of interior of tubes magnified, showing striated surface. 
 
 eter ; and having probably required, like the large existing brain-corai 
 (Meandrina) of the tropics, many centuries before their growth was 
 completed. 
 
 Different species of Crinoideans, or stone-lilies, are also common in 
 the same rocks with corals ; and, like them, must have enjoyed a firm 
 bottom, where their root, or base of attachment, remain.ed undisturbed 
 for years (c, fig. 365). Such fossils, therefore, are almost confined to 
 
 Fig. 365. 
 
 Apiocrinites rotundus, or Pear Encrinite ; Miller. Fossil at Bradford, Wilts. 
 a. Stem of Apiocrinites, and one of the articulations, natural size. 
 
 &. Section at Bradford of great oolite and overlying clay, containing the fossil encrinites. See text. 
 c. Three perfect individuals of Apiocrinites, represented as they grew on the surface of the Great 
 
 Oolite. 
 (I. Body of the Apiocrinites rotundus. 
 
 the limestones ; but an exception occurs at Bradford, near Bath, where 
 they are enveloped in clay. In this case, however, it appears that the 
 solid upper surface of the " Great Oolite" had supported, for a time, a 
 thick submarine forest of these beautiful zoophytes, until the clear and 
 still water was invaded by a current charged with mud, which threw 
 down the stone-lilies, and broke most of their stems short off near the 
 point of attachment. The stumps still remain in their original position ; 
 but the numerous articulations once composing the stem, arms, and body 
 of the zoophyte, were scattered at random through the argillaceous de- 
 
Cn. XX.] PECULIAR FOSSILS. SOT 
 
 posit in which some now lie prostrate. These appearances are lepre- 
 sented in the section 6, fig. 365, where the darker strata represent the 
 Bradford clay, which some geologists class with the Forest marble, oth- 
 ers 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 evi- 
 dence of the length of time they had lived on the spot, we find great 
 numbers of single joints, or circular plates of ihe stem and body of the 
 encrinite, covered^ over with serpulce. Now these serpulce 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 Bercnicca diluviana ; and many generations of these 
 mollusks had succeeded each other in the pure water before they became 
 fossil. 
 
 Fig. 366. 
 
 a. Single plate or articulation of an Encrinite overgrown with aerpula and bryozoa. Natural 
 
 size. Bradford clay. 
 &. Portion of the same magnified, showing the bryozoan Berenicea diluviana covering one of 
 
 the serpulce. 
 
 We may, therefore, perceive distinctly that, as the pines and cyca- 
 deous plants of the ancient " dirt bed," or fossil forest, of the Lower Pur- 
 beck 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 argil- 
 laceous deposits from each other, would be described by naturalists as 
 arising out of a difference in the stations of species ; but besides these, 
 there are variations in the fossils of the higher, middle, and lower part 
 of the oolitic series, which must be ascribed to that great law of change 
 in organic life by which distinct assemblages of species have been 
 adapted, at successive geological periods, to the varying conditions of 
 the habitable surface. In a single district it is difficult to decide how 
 
 * For a fuller account of these Encrinites, see Buckland's Bridgewater Treatise, 
 vol. i. p. 429. 
 
308 
 
 STONESFIELD SLATE. 
 
 [On. XX 
 
 far the limitation of species to certain minor formations has been due to 
 the local influence of stations, or how far it has been caused by time or 
 the creative and destroying law above alluded to. But we recognize 
 the reality of the last-mentioned influence, when we contrast the whole 
 oolitic series of England with that of parts of the Jura, Alps, and other 
 distant regions, where 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. Thui;- 
 man has shown how remarkably this fact holds true in the Bernese 
 Jura, although the argillaceous divisions, so conspicuous in England, are 
 feebly represented there, and some entirely wanting. 
 
 The Bradford clay above alluded to is sometimes 60 feet thick, but, 
 in many places, it is wanting ; and, in others, where there are no lime- 
 stones, it cannot easily be separated from the clays of xhe 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 celebrated as a 
 building-stone. In parts of Gloucestershire, especially near Minchin- 
 hampton, 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 neighborhood, and with fragments of 
 abraded madrepores, dicotyledonous wood, and crabs' claws. The shelly 
 strata, also, have occasionally suffered denudation, and the removed por- 
 tions have been replaced by clay."* In such shallow-water beds shells of 
 
 Fig. 368. 
 
 Fig. 367. 
 
 Terebratida digona. 
 Nat. size. Bradford clay. 
 
 Fig. 370. 
 
 Purpuroidea nodulata. nat. size. Cylindrites acutus, Sow. 
 Great Oolite, Minchinhampton. Syn. Actceon acutus. 
 
 Great Oolite, Minchinhampton. 
 
 Fig. 371. 
 
 Fig. 872. 
 
 Patella rugosa. Sow. 
 Great Oolite. 
 
 Nerlia costulata, Desh. fiimula (Emarginula) 
 Great Oolite. clathrata, Sow. Great Oolit. 
 
 * Lycett, Geol. Journ. vol. ir. p. 183. 
 
CH. XX.] STONESFIELD SLATE. 309 
 
 the genera Patella, Nerita, Rimula, and Cylindrites are common (see 
 figs. 369 to 372) ; while cephalopods are rare, and, instead of ammonites 
 and belemnites,- 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 car- 
 nivorous. They belong principally to the genera Buccinum, Pleurotoma, 
 Rostellaria, Murex, Purpuroidea (fig. 368), and FILSUS, and exhibit a 
 proportion of zoophagous species not very different from that which ob- 
 tains in warm seas of the recent period. These chronological results are 
 curious and unexpected, since it was imagined that ^e might look in 
 vain for the carnivorous trachelipods in rocks of such h.gh antiquity as 
 the Great Oolite, 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 contains 
 some pebbles of a rock very similar to itself, and which may be portions 
 of the deposit, broken up on a shore at low water or during storms, and 
 redeposited. The remains of belemnites, trigoniae, and other marine 
 shells, with fragments of wood, are common, and impressions of ferns, 
 cycadece, and other plants. Several insects, also, and, among the rest, 
 Fig. 3-73. the wing-covers of beetles are perfectly preserved (see fig. 
 373), some of them approaching nearly to the genus JZupres- 
 tis.\ The remains, also, of many genera of reptiles, such as 
 Pleiosaur, Crocodile, and 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 mammiferous 
 class. The student should be reminded that in all the rocks 
 described in the preceding chapters as older than the Eocene, 
 no bones of any land quadruped, or of any cetacean, have 
 6tonesfiid. been discovered until the Spalacotherium of the Purbeck beds 
 came to light in 1854 (see above, p. 295). Yet we have seen that ter- 
 restrial 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 
 
 * Proceedings Geol. Soc. voL i p. 414. 
 
 f See Buckland's Bridgewater Treatise ; and Brodie's Fossil Insects, where it 
 is suggested that these elytra may belong to Prionvs, 
 
310 
 
 FOSSILS OF THE OOLITE. 
 
 [Cii. XX. 
 
 from the great oolite of Enstone, near Woodstock, in Oxfordshire, was 
 cited, on the authority of Cuvier, as referable to this class. Dr. Buckland, 
 who stated this in his Bridge water Treatise (vol. i. p. 115), had the 
 kindness to send me the supposed ulna of a whale, that Professor Owen 
 might examine into its claims to be considered as cetacean. It is the 
 
 Fig. 874. 
 
 Bone of a reptile, formerly supposed to be the ulna of a Cetacean ; from the Great Oolite of 
 Enstone, near Woodstock. 
 
 opinion of that eminent comparative anatomist that it cannot have 
 belonged to the cetacea, because the fore-arm in these marine mammalia 
 is invariably much flatter, and devoid of all muscular depressions and 
 ridges, one of which is so prominent in the middle of this bone, rep- 
 resented in the above cut (fig. 374). In saurians, on the contrary, 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 Stones- 
 field 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 Phascolotherium 
 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 differing 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 
 
 Fig. 375. 
 Natural size. 
 
 Amphitherium Frevostii, Cuv. Sp. Stonesfleld slate. 
 a. Coronoid process. &. Condyle. c. Angle of jaw. d. Double-fanged molars 
 
CH. XX.] 
 
 OOLITIC GROUP AND ITS FOSSILS. 
 
 311 
 
 376 - 
 
 8late - 
 
 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 amount- 
 ing 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 maminifer, 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 sepa- 
 rate bones, as in fishes and most reptiles, or of two bones, united by a 
 suture, as in some few species belonging to those classes. The condyle, 
 moreover (6, 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 process (a, fig. 375) is well de- 
 veloped, whereas it is wanting, or very small, in the inferior classes of ver 
 tebrata. Lastly, the molar teeth in the Amphitherium and Phascolo- 
 tkerium have complicated crowns, and two roots (see d, fig. 375), in- 
 stead of being simple and with single fangs.* 
 
 The only question, therefore, which could fairly admit of controversy 
 was limited to this point, whether the fossil mammalia found in the 
 lower oolite of Oxfordshire ought to be referred to the marsupial quad- 
 rupeds, 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 Didelphys ; and Prof. 
 
 Tupaia Tana, 
 Eight ramus of lower jaw, 
 
 natural size. 
 
 A recent insectivorous mammal from 
 Sumatra. 
 
 Fig. 881. 
 
 Part of lower jaw of Tapaia Tana; 
 
 twice natural size. 
 Fig. 289. End view seen from behind, showing 
 
 the very slight inflection of the angle at c. 
 Fig. 290. Side view of same. 
 
 Part of lower jaw of Didelphys Azarae, ; 
 
 recent, Brazil. Natural size. 
 Fig. 291. End view seen from behind, showing 
 
 the inflection of the angle of the jaw, c, a. 
 Fig. 292. Side view of same. 
 
 * I have given a figure in the Principles of Geology, chap, ix., of another 
 Stonesfield specimen of Amphitherium Prevostii, in which the sockets and roots 
 of the teeth are finely exposed. 
 
312 OOLITIC GROUP [OH. XX 
 
 Owen has since established its generality in the entire marsupial series. 
 In all these pouched quadrupeds, this process 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. Water- 
 house 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 pro- 
 cess (c) bent inwards in a slighter degree than in any of the known mar- 
 supialia ; in short, the inflection does not exceed that of the mole or 
 hedgehog. This fact turns the scale in favor of its affinities to the placental 
 insectivora. Nevertheless, the Amphitherium offers some points of approxi- 
 mation in its osteology to the marsupials, especially to the MyrmecoUus, 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. 311), which differs from the former (fig. 375) principally in being 
 larger. 
 
 The second mammiferous genus discovered in the same slates was 
 named originally by Mr. Broderip Didelphys BucJclandi (see fig. 382), 
 
 Fig. 3S2. 
 
 Phascolotherium Bucklandi, Broderip, sp. 
 a. Natural size. &. Molar of 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.f 
 
 On reviewing, therefore, the whole of the osteological evidence, it will 
 be seen that we have every reason to presume that the Amplitherium 
 and Phascolotherium of Stonesfield represent both the placental and mar- 
 supial 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 nega- 
 tive evidence. The singular accident of our having as yet found nothing 
 but the lower jaws of seven individuals, and no other bones of their skele- 
 tons, is alone sufficient to demonstrate the fragmentary manner in which 
 the memorials of an ancient terrestrial fauna are handed down to us. 
 
 * A figure of this recent Myrmecoblus will be found in the Principles, chap. ix. 
 f Owen's British Fossil Mammals, p. 62. 
 
CH. XX.] AND ITS FOSSILS. 313 
 
 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 Dieman's Land, so also is it in the Australian seas, that 
 we find the Cestracion, a cartilaginous fish 
 which has a bony palate, allied to those called 
 Acrodus (see fig. 412, p. 321) 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 fre- 
 quently met with in the Stonesfield slate. So, 
 also, the Araucarian pines are now abundant, 
 together with ferns, in Australia and its islands. Portion "^ 
 as they were in Europe in the oolitic period. focarya magnified. (Bnck- 
 
 J r land s Bridgrw. Treat PI. 63.) 
 
 Endogens of the most perfect structure are met inferior Oolite, Channouth, 
 with in oolitic rocks, as, for example, the Podo- 
 
 carya 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 northeast, is 
 represented by flaggy and fissile sandstones, as at Collyweston in North- 
 amptonshire, where, according to the researches of Messrs. Ibbetson and 
 Morris,* it contains many shells, such as' Trigonia angulata, 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 northwest 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 representa- 
 tive of the Great Oolite ; but the scarcity of marine fossils makes all com- 
 parisons with the subdivisions adopted in the south extremely difficult 
 A rich harvest of fossil ferns has been obtained from the upper carbona- 
 ceous 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 and Unio t collected by Mr. Bean from these Yorkshire 
 coal-bearing beds, point to the estuary or fluviatile origin of the deposit. 
 
 * Ibbetson and Morris, Report of Brit. Ass., 1847, p. 131 ; and Morris, GeoL 
 Journ n ix. p. 334. 
 
314 
 
 OOLITIC GROUP 
 Fig. 884. 
 
 [CH. XX. 
 
 PteropJiyllum comptum. Syn. Cycadites comptus. 
 Upper sandstone and shale, Gristhorpe, near Scarborough. 
 
 Fig. 386. 
 
 Hemitelites Brmcnii, Goepp. 
 Syn. Phlebopteris contigua, Lind. & Hutt. 
 
 Upper carbonaceous strata, Lower Oolite, Gristhorpe, Yorkshire. 
 
 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 sec- 
 ondary rock in England. One seam of coal of good quality has been 
 worked 3 j- feet thick, and there are several feet more of pyritous coal 
 resting upon it. 
 
 Fuller's Earth (h, Tab. p. 291). 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 England. It abounds in the small oyster 
 represented in fig. 386. 
 
 Inferior Oolite. This formation consists of a calcare- 
 ous freestone, usually of small thickness, 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 Terebratula fimbria (fig. 387), Rhynchonella spinosa 
 (fig. 388), and Pholadomya fidicula (fig. 389). The extinct genus 
 Pleurotomaria is also a form very common in this division as well as in 
 the Oolitic system generally. It resembles the Trochus in form, but is 
 
AND ITS FOSSILS. 
 
 Fig. 3SS. 
 
 315 
 
 Fig. 389. 
 
 Terebratula fimbria. EhynchoneUa spinosa. a. PJwladomyafidicula. % nat. size. Inf. Ool. 
 Inferior Oolite. Inferior Oolite. &. Heart-shaped anterior termination of the 
 
 same. 
 
 Fig. 391. 
 
 Fig. 392. 
 
 Pleurotomaria granulata. 
 
 Ferruginous Oolite, Normandy. 
 
 Inferior Oolite, England. 
 
 Pleurotomaria omata, Sow. Sp. 
 Inferior Oolite. 
 
 Disaster ringens. 
 Inf. Ool. Somersetshire. 
 
 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. 893. 
 
 Ammonites Humphresianu*. 
 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. 
 
316 
 
 Fig. 394. 
 
 LNFEKIOR OOLITE. 
 6 
 
 Ammonites margaritatus, D'Orb. Syn. A. StoJcesii, Sow, 
 Lias. 
 
 Pig. 896. 
 
 Ammonites Brailcenridgii, Sow. 
 
 Great Oolite, Scarborough. 
 Inf. Ool. Dundry; Calvados; &c. 
 
 Fig. 397. 
 
 Ostrea MarsMi. % nat size. 
 Middle and Lower Oolite. 
 
 Ammonites striatulus, Sow. 
 
 i 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 spe- 
 cies common to older and newer groups, yet these groups are distinguish- 
 able from one another by a comparison of the whole assemblage of fossil 
 shells proper to each. 
 
CH. XXL] MINERAL CHARACTER OF THE LIAS. 317 
 
 CHAPTER XXI. 
 JURASSIC GROUP continued. LIAS. 
 
 Mineral character of Lias Name of Gryphite limestone Fossil shells and fish 
 Radiata Ichthyodorulites Reptiles of the Lias Ichthyosaur aud 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 calca- 
 reous 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 
 
 Fig. 399. 
 
 iiaR^///////^ 
 Fig 398. 
 
 Avicula incequivalvis, Sow. Avicula cygnipes, Phil. 
 
 Lower Oolite. Marlstone, Gloucestershire ; Lias, Yorkshire. 
 
 traced throughout a great part of Europe as a separate and independent 
 group, of considerable thickness, varying from 500 to 1000 feet, contain- 
 ing 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 Eng- 
 land, France, and Germany, is an alternation of thin beds of blue or gray 
 limestone, having a surface which becomes light-brown when weathered, 
 
318 NAME OF " GKYPHITE LIMESTONE." [On. XXL 
 
 these beds being separated by dark-colored 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 th 
 other. 
 
 Although the prevailing color of the limestone of this formation is 
 blue, yet some beds of the lower lias are of a yeLowish white color, and 
 have been called white lias. In some parts of France, near the Vos^es 
 
 1 / o 
 
 mountains, and in Luxembourg, M. E. de Beaumont has shown that the 
 lias containing GrypJicea 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 contains of a 
 
 Fig. 400. 
 
 Fig. 401. 
 
 GrypTiwa incurva, Sow. 
 
 (G. arcuata, Lam.) 
 
 Lias. 
 
 Plagiostoma (Lima) giganteum^ Sow. 
 Inf. Ool. and Lias. 
 
 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 secondary rocks in which brachi- 
 opoda of the genera Spirifer and Leptcena (figs. 403, 404) occur : no 
 less than nine species of Spirifers are enumerated by Mr. Davidson as 
 belonging to the lias. These palliobranchiate 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 Briareus 
 
 * Conyb. and Phil. p. 261. 
 
CH. XXL] FOSSILS OF THE LIAS. 
 
 Fig. 402. Fig. 403. 
 
 319 
 
 Spirifer WalcotU, Sow 
 Lower Lias. 
 
 Hippopodium ponderosum, Sow. 
 \ diam. Lias, Cheltenham. 
 
 Fig. 405. 
 
 Nautilus truncatus. Lias. 
 Fig. 407. 
 
 Leptcena Moorei, Dav. 
 Upper Lias, Ilmtnster. 
 
 Fig. 406. 
 
 Ammonites Nodotianu* f 
 
 A. striatulus. Sow. 
 
 Lias. 
 
 Ammonites Bifrons, Brug. 
 A. WalcotU, Sow. 
 Upper Lias shales. 
 
 (fig. 408) is conspicuous. Of Ophioderma Egertoni (fig. 409), referable 
 to the OpkiurcB of Muller, perfect specimens have been met with in the 
 marlstone beds of Dorset and Yorkshire. 
 
320 
 
 FOSSILS OF THE LIAS. 
 
 . XXL 
 
 Fig. 408. 
 
 Fig. 409. 
 
 Extracrinus Briareus. nat. size. 
 (Body, arms, and part of stem.) 
 Lias, Lyme Kegis. 
 
 OpModerma Egertoni, E. Forbes. 
 Lias Marlstone, Lyme Eegis. 
 
 The Extracrinus Briareus (removed by Major Austin from Pentacri- 
 nus 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 Crinoid, with its innumerable tentacular arms, appears to have been 
 frequently attached to the drift-wood of the liassic sea, in the same man- 
 ner 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, Apiocri- 
 nus, and many others. 
 
 The fossil fish re- Fi ?- 41 - 
 
 semble generically 
 those of the oolite, 
 belonging all, ac- 
 cording to M, Agas- 
 siz, to extinct gen- 
 era, and differing 
 for the most part 
 from the ichthyolites 
 of the Cretaceous pe- 
 
 Scales of Lepidotus gigas. 
 a. Two of the scales detached. 
 
CH. XXL] 
 
 FOSSILS OF THE LIAS. 
 
 321 
 
 riod. Among them is a species of Lepidotus (L. yigas, Agas.), fig. 410, 
 which is found in the Has of England, France, and Germany.* This 
 genus was before mentioned (p. 262) 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 
 jEchmodus (see fig. 411), is almost exclusively Liassic. The teeth of a 
 species of Acrodus, also, are very abundant in the lias (fig. 412). 
 
 6 a Tig. 411. 
 
 I. Scales of JSchmodus 
 Leachii. 
 
 a. jEchmodus Ecstored outline. 
 Fig. 412. 
 
 c. Scales of Dape- 
 dius monUifer. 
 
 Acrodvs nobttis, Agas. (tooth) ; commonly called fossil leach. 
 Lias, Lyme Kegis and Germany. 
 
 But the remains of fish which have excited more attention than any 
 others, are those large bony spines called iehthyodorulites (a, fig. 413), 
 which were once supposed by some naturalists to be jaws, and by others 
 
 Fig. 413. 
 
 Hybodv* reticulatug, Agas. Lias, Lyme Eegis. 
 
 a. Part of fin, commonly called Ichthyodorulite. 
 5. Tooth. 
 
 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 articulation in the iehthyodorulites. These last 
 
 * Agassiz, Pois. Fos. vol :i. tab. 28, 29. 
 21 
 
322 REPTILES OF THE LIAS. [On. XXL 
 
 appear to have been bony spines which formed the anterior part of the 
 dorsal fin, like that of the living genera Cestracion and Chimcera (see a, 
 fig. 414). In both of these genera, the posterior concave face is armed 
 
 Fig. 414. 
 
 Chimcera monstrosa* 
 a. Spine forming anterior part of the dorsal fin. 
 
 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 imbed- 
 ded in the flesh, and attached to strong muscles. " They serve," says 
 Dr. Buckland, "as in the Chimcera (fig. 414), to raise and depress the 
 fin, their action resembling that of a movable 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 Ichthyosaurus, 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.J It is evident from their fish-like vertebra, their paddles, re- 
 sembling 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, in- 
 dicate 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 cartilaginous 
 rays that bifurcate as they approach the edge, like those in the fin of a 
 fish (see a, 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 
 
 * Agassiz, Poissons Fossiles, vol. iii. tab. C. fig. 1. 
 
 f Bridgewater Treatise, p. 290. + Ibid. p. 168. Ibid. p. 187. 
 
CH. XXI] 
 
 LIAS SAUKIANTS. 
 
 323 
 
 beyond its osseous framework, and 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 without radiating bones, and purely tegumentary, expanding in a 
 vertical direction ; an organ of motion which enabled them to turn 
 their heads rapidly .f 
 
 * GeoL Soc. Transact Second Series, vol. vi. p. 199, pL xx. 
 f Gcol. Soc. Transact. Second Series, YoL v. p. 511. 
 
324 LIAS SAURIANS. [Cit XXI. 
 
 Fig. 417. 
 
 Posterior part of hind fin or paddle of Ichthyosaurus communis. 
 
 Mr. Conybeare was enabled, in 1824, after examining many skeletons 
 nearly perfect, to give an ideal restoration of the osteology of this genus, 
 and of that of the Plesiosaurus* (See figs. 415, 416.) The latter an- 
 imal 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 Ichthyosaur, and our modern cetacea.f 
 Some of the reptiles above mentioned were of formidable dimensions. 
 One specimen of Ichthyosaurus platyodon, from the lias at Lyme, now in 
 the British Museum, 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. Stutchburg has 
 suggested that their bodies after death became inflated with gases, and, 
 while the abdominal viscera were decomposing, the bones, though dis- 
 united, were retained within the tough dermal covering as in a bag, until 
 the whole, becoming water-logged, sank to the bottom.]; As they be- 
 longed to individuals of all ages, they are supposed, 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 extinct 
 saurians must have inhabited the sea ; and it was urged that, as there 
 are now chelonians, like the tortoise, living in freshwater, and others, 
 
 * Geol. Trans. Second Series, vol. i. pi. 49. 
 
 f Conybeare and De la Beche, Geol. Trans. 1st Ser. vol. v. p. 559 ; and Buck- 
 land, Bridgw. Treatise, p. 203. 
 
 J Quarterly Geol. Journal, vol. ii. p. 4 1 1. 
 
CH. XXL] LIAS SAURIANS. 325 
 
 as the turtle, frequenting the ocean, so there may have been formerly 
 some saurians proper to salt, others to fresh water. The common croco- 
 dile 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 re- 
 cently a saurian has been discovered 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 vhe 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 tfhole archipelago, 
 there is only one rill of fresh water that reaches the coast The soil is 
 for the most part dry and harsh, and the vegetation scanty. The b'.rds, 
 reptiles, plants, and insects are, with very few exceptions, of species 
 found nowhere 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, tortoises, 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 Iguanidoe of Bell, and to a peculiar genus 
 (Amblyrhynchus) established by that naturalist, and so named from 
 their obtusely truncated head and short snout.* Of these lizards one 
 is terrestrial in its habits, and burrows in the ground, swarming every- 
 where on the land, having a round tail, and a mouth somewhat resem- 
 bling in form that of the tortoise. The other is aquatic, and has its tail 
 flattened laterally for swimming (see fig. 418.) "This marine saurian," 
 
 Fig. 418. 
 
 AtnttyrTiyncTius cristatw, Bell. Length varying from 3 to 4 feet The only existing marine 
 lizard now known. 
 
 a. Tooth, natural size and magnified. 
 amblys, blunt ; and pvyxos, rhynchus, snout. 
 
326 SUDDEN DESTRUCTION OF SAUEIANS. [Cn. XXI. 
 
 says Mr. Darwin, " is extremely common on all the islands throughout 
 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 color, 
 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 sin- 
 gular fact, considering its abundance, and that the natives are well 
 acquainted with the eggs of the terrestrial AmUyrhynchus, which is also 
 herbivorous."* 
 
 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 rep- 
 tiles ; 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. Wot unfrequently there are layers of 
 these coprolites, at different depths in the lias, at a distance from any 
 
 * Darwin's Journal, chap. xix. f Bridges. Treat, p. 125. 
 
CH. XXL] FOSSILS OF THE LIAS. 327 
 
 entire skeletons of the marine lizards from which they were derived " as 
 ifj" says Sir H. De la Beche, " the muddy bottom of the sea received 
 small sudden accessions of matter from time to time, covering up the 
 coprolites and other exuviae which had accumulated during the inter- 
 vals."* It is farther stated that, at Lyme Regis, those surfaces only of 
 the coprolites which lay uppermost &t the bottom of the sea have suf- 
 fered partial decay, from the action of water before they were covered 
 and protected by the muddy sediment that has afterwards permanently 
 enveloped them.f 
 
 Numerous specimens of the Calamary, or pen-and-ink fish (Geoteuthis 
 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 impregnated with carbcuate 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.^ 
 
 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 earthquakes, as in Java, 
 in 1699 ; and that undescribable multitudes of dead fishes have been 
 seen floating on the sea after a discharge of noxious vapors during simi- 
 lar 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 Gloucestershire, 
 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 insects and plants have been 
 detected in several places, mingled with marine shells ; but in the infe- 
 rior 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, anci with 
 some nearly entire beetles, of which the eyes are preserved. The ner- 
 vures of the wings of neuropterous insects (fig. 419) are beautifully per- 
 
 * Geological Researches, p. 334. 
 
 f Buckland, Bridgew. Treat, p. 307. t Ibid. 
 
 See Principles, Index, Lancerote, Graham Island, Calabria. 
 
 || A history of Fossil Insects, <tc. 1846. Londoa 
 
328 FOSSIL PLANTS. [Cn. XXI. 
 
 Fig. 410. f ec t i n this bed. Ferns, with leaves of mo 
 
 nocotyledouous plants, and some apparently 
 brackish and freshwater shells, accompany 
 the insects in several places, while in others 
 
 Nat size< marine shells predominate, the fossils varying 
 
 Wing of a nenropterous insect, from -111 
 
 the Lower Lias, Gloucestershire, apparently as we examine the bed nearer or 
 farther from the ancient land, or the source 
 
 whence the freshwater 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. Westwood declares that they comprise both wood- 
 eating and herb-devouring beetles of the Linnean genera Elater, Cara- 
 bus, &c., besides grasshoppers (Gryllus), and c.-etached wings of dragon- 
 flies and may-flies, or insects referable to the Linnean genera Libellula, 
 Ephemera, Hemerobius, 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 as- 
 sociated organic remains of other classes must lead to a different conclu- 
 sion. 
 
 Fossil plants. Among the vegetable remains of the Lias, several 
 species of Zamia have been found at Lyrne Regis, and the remains of 
 coniferous plants at Whitby. Fragments of 
 wood are common, and often converted into 
 limestone. That some of this wood, though 
 now petrified, was soft when it first lay at 
 the bottom of the sea, is shown by a speci- 
 men 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 
 Nilsonia, and among the ferns the numerous genera with leaves having 
 reticulated veins (as in fig. 385, p. 314), are mentioned as botanical 
 characteristics of this era.* The absence as yet from the Lias and Oolite 
 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. 266). The angiosperms seem, there- 
 fore, 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 endeavor to restore, in 
 imagination, the ancient condition of the European area at the period of 
 the Oolite and Lias, we must conceive a sea in which the growth of 
 
 * Tableau des Veg. Fos. 1849, p. 105 
 
Ca XXL] OEIGIN OF THE OOLITE AND LIAS. 329 
 
 coral reefs and shelly limestones, after proceeding without interruption 
 for ages, was liable to be stopped suddenly by the deposition of clayey 
 sediment Then, again, the argillaceous matter, devoid 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 cal- 
 careous sand, or solid rocks of shell and coral, to be again succeeded by 
 the recurrence of another period of argillaceous deposition. Mr. Cony- 
 beare 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 lime- 
 stone (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 followed 
 over larger areas than the sands or sandstones.^ It should also be re- 
 membered that while the oolitic system becomes arenaceous, and resem- 
 bles 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, in reality, retain a pretty uniform 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 department of 
 the Haute Saone, in France, may be equal in thickness to that of Eng- 
 land ; 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.J; 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 imagine, 
 first, the bed of the ocean to be the receptacle for ages of fine argilla- 
 ceous sediment, brought by oceanic currents, which may have communi- 
 cated 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 sub- 
 merged, or because the current is deflected in another direction by the 
 altered shape of the bed of the ocean and neighboring dry land. By 
 such changes the water becomes once more clear and fit for the growth 
 of stony zoophytes. Calcareous sand is then formed from comminuted 
 shell and coral, or, in some cases, arenaceous matter replaces the clay ; 
 because it commonly happens that the finer sediment, being first drifted 
 farthest from coasts, is subsequently overspread by coarse sand, after the 
 
 * Con. and Phil. p. 166. f Geol. Researches, p. 387. 
 
 \ Burat's D'Aubuisson, torn. ii. p. 456. 
 
330 OOLITE AND LIAS [Cn. XXI 
 
 sea lias 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 sinking down 
 like that which is now taking place in some existing regions of coral 
 between Australia and South America. The occurrence of subsidences, 
 on so vast a scale, may have caused the bed of the ocean and the adjoin- 
 ing land, throughout great parts of the European area, to assume a 
 shape favorable to the deposition of another set of clayey strata ; and 
 this change may have been succeeded 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 imbedded. 
 
 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 oc- 
 curring in a depression of the granite rocks (see section, fig. 421), which 
 
 Section showing the geological position of the James Eiver, or East Virginian Coal-field. 
 
 A. Granite, gneiss, &c. B. Coal-measures. 
 
 C. Tertiary strata. D. Drift or ancient alliwium. 
 
 Professor W. B. Rogers first correctly referred to 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, calamites, and equisetums, and these last are very commonly 
 met with in a vertical position more or less compressed perpendicularly. 
 It is .clear that they grew in the places where they are now buried in 
 strata of hardened sand and mud. I found them maintaining their erect 
 attitude, at points many miles distant from others, in beds both above 
 
CH. XXI] OF THE UXITED STATES. 331 
 
 and between the seams of coal. In order to explain this fact we must 
 suppose such shales and sandstones to have been gradually accumulated 
 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 up- 
 light position. One of the Virginian fossil ferns, Pecopteris Whitbyensis, 
 is also a species common to the Yorkshire 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 cham- 
 ber 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 analyzed 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 Tetra- 
 gonolepis (^Echmodus), see fig. 411, and to a new genus which I have 
 called Dictyopyge. Shells are very rare, as usually in all coal-bearing de- 
 posits, but a species of Posidonomya is in such profusion in some shaly 
 beds as to divide them like the plates of mica in micaceous shales 
 (see fig. 422). 
 
 Fig. 422. 
 
 a. Posidonomyd) or Estheria ft " &. Toang of same. 
 
 Oolitic coal-shale, Eichmond, Virginia. 
 
 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. 
 
 * See description of the coal-field by the author, and of the plants by C. J. F. 
 Bunbury, Esq., Quart GeoL Journ. voL iii. p. 281. 
 
 f Possibly, as suggested by Prof. Morris (Geol. Journ. vol. iii. p. 2*75), these 
 delicate bivalves may prove to belong to the crustacean genus Estheria. 
 
NEW RED SANDSTONE. 
 
 [Cn. XXII. 
 
 CHAPTER XXIL 
 
 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 Chcirotherium in Eng- 
 land and Germany Osteology of the Lnbyrinthodon Identification of this 
 Batrachian with the Cheirotherium Triassic mammifer Origin of Red Sand- 
 stone and Rock-salt Hypothesis of saline volcanic exhalations Theory of the 
 precipitation of salt from inland lakes or lagoons Saltness of the Red Sea 
 New Red Sandstone in the United States Fossil footprints of birds and rep- 
 tiles in the Valley of the Connecticut Antiquity of the Red Sandstone con- 
 taining them. 
 
 BETWEEN the Lias and the Coal, or Carboniferous group, there is in- 
 terposed, 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 (6). 
 
 Fig. 423. 
 
 a. New red sandstone. 
 
 &. 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 
 color of most of the rocks of this group, causes a strong contrast between 
 it and the Jurassic formations before described. 
 
 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 inter- 
 mediate in position between the Lias and Coal ; and the term " Poi- 
 kilitic" was proposed by Messrs. Conybeare and Buckland,* from rfojxiXos, 
 variegated, some of the most characteristic strata of this group having 
 been called variegated by Werner, from their exhibiting spots and streaks 
 of light blue, green, and buff color, in a red base. 
 
 * Buckland, Bridg. Treat, vol. ii. p. 83. 
 
CH. XXIL1 KEUPER AND MUSCHELKALK FORMATIONS. 
 
 333 
 
 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. 
 
 Trias or Upper 
 New Red 
 Sandstone - 
 
 German. French, 
 
 a. Saliferous and gyp- ) 
 
 seous shales and > Keuper - - Marnes Irishes, 
 sandstone } 
 
 6. (wanting in England) 
 
 c. Sandstone and quart- ) Bunter-sand- \ r . ^V^A 
 zose conglomerate \ stein - - \ Gr6s blgarre " 
 
 Fig. 424. 
 
 I shall first describe this group as it occurs in Southwestern and 
 Northwestern 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 " Bunter-sandstein." 
 
 The Keuper, the first or newest of these, is 1000 feet thick in Wiir- 
 temberg, and is divided by Alberti into sandstone, gypsum, and carbona- 
 ceous 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 Sauricthys and Gy- 
 rolepis (figs. 433, 434, p. 336). The plants 
 of the Keuper are generically very analogous 
 to those of the lias and oolite, consisting oi 
 ferns, equisetaceous plants, cycads, and coni- 
 fers, with a few doubtful monocotyledons. A 
 few species, such as Equisetites columnaris, 
 are common to this group, and the oolite. 
 The Muschelkalk consists chiefly of a compact, grayish limestone, but 
 includes beds of dolomite in many places, together with gypsum and 
 rock-salt. This limestone, a rock wholly unrepresented in England, 
 abounds in fossil shells, as the name implies. Among the cephalopoda 
 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'bj DeHaan, in which the descending lobes (see a, 6, c, fig. 425) 
 terminate in a few small denticulations pointing inwards. Among the 
 
 * Monog. des Bunten Sandsteins. 
 
 Equisetites columnaris, 
 Equisetum columnare.) 
 ment of stem, and small portion 
 of same magnified. Keuper. 
 
334 
 
 THE BUNTER-SANDSTEIN. 
 a Fig. 425. & 
 
 [On. XXII. 
 
 Ceratites nodosus. Muschelkalk. 
 
 a. Side view. &. Front view, 
 
 c. Partially denticulated outline of the septa dividing the chambers. 
 
 bivalve shells, the Posidonia minuta, Goldf. (Posidonomya minuta, 
 Bronn) (see fig. 426), is abundant, ranging through theKeuper, Muschel- 
 kalk, and Bunter-sandstein ; and Avicula 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. Aviciila socialis. &. Side view of same. 
 
 Goldf. (Posido- Characteristic of the Muschelkalk. 
 
 nomya minuta, 
 Bronn.) 
 
 The abundance of the heads and. stems of lily encrinites, JEncrinus 
 Fig.42S. 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 Aspidum loricata (fig. 429) is as yet peculiar 
 
 Fig. 429. 
 
 Encrinus liliiformis, Schlott. Syn. K monttiformis. 
 
 Body, arms, and part of stem. 
 
 a. Section of stem. 
 
 Muschelkalk. 
 
 Aspidura loricata, Agas. 
 a. Upper side. 
 &. Lower side. 
 Muschelkalk. 
 
CIL XXIL] THE BUNTER-SANDSTEIN. 335 
 
 to the Musclielkalk. In the same formation are found ganoid fish with 
 heterocercal tails, of the genus Placodus. (See fig. 430.) 
 
 Fig. 430. Fig. 431. 
 
 a. Yolteia heterophyUa. (Syn. Vottsia 
 
 brevifolia.) 
 &. Portion of same magnified to show 
 
 > fit/ '^*&* f *' f / fructification. Sulzbai 
 
 Bunter-sandstein. 
 
 Palatal teeth of Plncodus gigas. 
 Muschelkalk. 
 
 The Bunter-sandstein consists of various colored sandstones, dolomites, 
 and red-clays, with some beds, especially in the Hartz, of calcareous piso- 
 lite 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 Ldbyrinthodon, to belong to this lowest mem- 
 ber of the Triassic group. At Sulzbad (or Soultz-les-bains), near Stras- 
 burg, on the flanks of the Vosges, many plants have been obtained from 
 the " bunter," especially 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, enu- 
 merated 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 neighborhood of 
 Strasburg), and its peculiarities may be local. 
 
 The footprints of a reptile (Labyrinthodori) have been observed on the 
 clays of this member of the Trias, near Hildburghausen, in Saxony, im- 
 pressed 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 deposi- 
 tion 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 neighbor- 
 hood of Axmouth, in Devonshire, and in the cliffs of Westbury and 
 
 * Tableau des Genres de Veg. Foa., Diet. Univ. 1849. 
 
336 
 
 TRIASSIC GROUP IN ENGLAND. 
 
 [On. XXII. 
 
 Aust, in Gloucestershire, on the banks of the Severn, a dark-colored 
 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 Acro- 
 dus, Hybodus, Gyrolepis, and Saurichthys. 
 
 Among those common to the English bone-bed and the Muschelkalk 
 of Germany are Hybodus plicatilis (fig. 432), Saurichthys apicalis 
 (fig. 433), Gyrolepis tennis triatus (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. 
 
 Fig. 432. 
 
 Hybodus plicatilis. Teeth. Bono-bed. 
 Aust and Axmouth. 
 
 Saurichthys apicalis. 
 Tooth : nat. size, and 
 magnified. Axmouth. 
 
 Gyrolepis tenuistriatus. 
 Scale ; nat. size, and 
 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. 334). 
 
 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 Shrews- 
 bury. 
 
 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 argilla- 
 ceous beds, the origin of which will be spoken of in the sequel. 
 
 The lower division or English representative of the " Bunter" attains 
 
 * Geol. Trans., Sec. Ser., vol. v. p. 318, <fec. 
 
Fig. 435. 
 
 CH. XXIL] FOSSIL FOOTSTEPS IX NEW RED SANDSTONE. 337 
 
 a thickness of 600 feet in the counties last mentioned. Besides red and 
 green shales and red sandstones, it comprises much soft white quartzose 
 sandstone, in which the trunks of silicified trees have been met with at 
 Allesley Hill, near Coventry. Several of them were a foot and a half in 
 diameter, and some yards in length, decidedly of 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 remarkable 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 Hildburg- 
 hausen, in Saxony, to which I have already al- 
 luded. 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 hu- 
 man hand. (See fig. 435.) The footmarks at 
 Hesseberg are partly concave and partly in re- 
 lief; the former, or the depressions, are seen 
 upon the upper surface of the sandstone slabs, 
 but those in relief are only upon the lower sur- 
 faces, 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 and a half), 
 
 Fig. 436. 
 
 Single footstep of Cheirothe- 
 rium. Banter Sandstein, 
 Saxony ; one-eighth of nat. 
 size. 
 
 Line of footsteps on slab of sandstone. Hildburghausen, in Saxony. 
 
 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 corresponding age 
 at Storton Hill, were imprinted on five thin beds of clay, superimposed one 
 upon the other in the same quarry, and separated by beds of sandstone. 
 On the lower surface of the sandstone strata, the solid casts of each impres- 
 
 * Buckland, Proc. Geol. Soc. voL ii. p. 439 ; and Murchison and Strickland. 
 Geol. Trans. Second Ser. vol. v. p. 347. 
 
 22 
 
338 FOSSIL KEMAINS OF LABYRINTHODON. [On. XXII 
 
 sion 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. Cun- 
 ningham discovered (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, anatomists 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 desig- 
 nated some of the footsteps as those of a small web-footed animal, prob- 
 ably crocodilean. 
 
 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 Ckeirotherium 
 and other animals walked, leaving impressions of their footsteps, and that 
 each layer had been afterwards submerged by a sinking down of the sur- 
 face, 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 impres- 
 sions 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 sand- 
 stone of Warwick and Leamington (fig. 437), that neither of them could 
 be referred to true saurians, although they had been named Masto- 
 donsaurus and Phytosaurus by Jager. It appeared that they were -of 
 the Batrachian order, and attested the former ex- 
 istence of frogs of gigantic dimensions in compari- Fi - 437 - 
 son with any now living. Both the Continental 
 and English fossil teeth exhibited a most compli- 
 cated texture, differing from that previously ob- 
 served in any reptile, whether recent or extinct, but 
 
 i i , ,1 7-7j7 Tooth of LabyrintJwdon ; 
 
 most nearly analogous to the Ichthyosaurus. A nat. size. Warwick sand- 
 section of one of these teeth exhibits a series of 6tone ' 
 irregular folds resembling the labyrinthic windings of the surface of 
 the brain ; and from this character Prof. Owen has proposed the name 
 Labyrinthodon for the new genus. The annexed representation (fig. 
 
CH. XXII.] FOSSIL REMAINS OF LABYRINTHODON. 
 
 339 
 
 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.433. 
 
 Transverse section of tooth of Labyrinthodon Jaegeri, Owen (Mastodonsaurus Jaegerl^ 
 
 Meyer) ; nat size, and a segment magnified. 
 a. Palp cavity, from which the processes of pulp and dentine radiate. 
 
 When Prof. Owen had satisfied himself, from an inspection of the cra- 
 nium, 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 formation, 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 Cheirotherium 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 ani- 
 mal ; 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 originated 
 from an animal walking under water. 
 
 It is true that the structure of the foot is still wanting, and that a more 
 connected and complete skeleton is required for demonstration ; but the 
 circumstantial evidence above stated is strong enough to produce the 
 
340 FOSSILS EEMAINS OF LABYRrNTHOIHDN. [Cn. XXII 
 
 conviction that the Cheirotherium and Ldbyrinthodon are one and the 
 same. 
 
 In order to show the manner in which one of these formidable Batra- 
 chians may have impressed the mark of its feet upon the shore, Prof. 
 Owen has attempted a restoration, of which a reduced copy is annexed 
 
 Fig. 439. 
 
 Eestored outline of Labyrinthodon pachygnathm, 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 Labyrinthodons 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 charac- 
 ters, are considered by Messrs. Jager and Owen to give them superior 
 claims to be classed as batrachians. 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 description of two 
 fossil molar teeth, referred by him to a warm-blooded quadruped,* which 
 he obtained from a bone-breccia in Wiirtemberg 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 Stutt- 
 gart, 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, 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. 
 
 * "Wiirtembergisch. Naturwissen Jahreshefte, 3 Jahr. Stuttgart, 1847. 
 f Nov. Act. Acad. Caesar. Leopold. Nat. Cur. 1850, p. 902. For figures, see 
 ibid, plate xxi. figs. 14, 15, 1&, 17. 
 
CH. XXIL] FOSSIL MAMMIFER IN TRIAS. 
 
 Fig. 440. 
 
 341 
 
 Jfict'olestes antiquus, Plieninger. Molar tooth magni- 
 fied. Upper Trias, Diegerloch, near Stuttgart, Wiir- 
 ttmberg. 
 
 a. View of inner side ? &. Same, outer side ? 
 
 c,. Same in profile. d. Crown of same. 
 
 Molar of Mivroles- 
 tent Plien.4times 
 as large as the fig. 
 440. From the 
 trias of Diegerloch, 
 Stuttgart 
 
 Microleste* antiquu^ 
 Plien. . 
 
 View of same molar 
 as No. 440. From & 
 drawing by Her- 
 mann Von Meyer, 
 a. View of inner 
 
 side? 
 &. Crown of same. 
 
 Professor Plieninger inferred in 1847, from the Fig. 442. 
 
 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, prob- 
 ably insectivorous, he calls it Microlestes, from pxpos, 
 little, and X^o^s, a beast of prey. Soon afterwards, 
 he found the second tooth, also at the same locality, 
 Diegerloch, about two miles to the southeast of Stutt- 
 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, differing in structure 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, 441, 442, and the descriptions of Prof. Plieninger, observes, 
 that not only the double roots of the teeth, and their crowns presenting 
 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 distinguishing them from 
 fish and reptiles. " The arrangement of the six cusps or tubercles in two 
 rows, in fig. 440, with a groove or depression 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 be- 
 longed. 
 
 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 recognize its affinity 
 with any mammalian type, recent or extinct, known to him. 
 
 It has already been stated that the stratum in which the above-men- 
 tioned fossils occur is intermediate between the lias and the uppermost 
 
34:2 ORIGIN OF RED SANDSTONE [On, XXII 
 
 member of the trias. That it is really triassic may be deduced from the 
 following considerations. In Wurtemberg there are two " bone-beds," 
 one of great extent, and very rich in the remains of fish and reptiles, 
 which intervenes between the muschelkalk and keuper ; the other, con- 
 taining 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 Axmouth and Aust- 
 cliff near Bristol, which is shown above, p. 336, to include characteristic 
 species of muschelkalk fish, of the genus Saurichthys, Hylodus, and 
 Gyrolepis. In both the Wurtemberg 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 miraUlis. The saurian called Belodon by H. Von Meyer, 
 of the Thecodont family, is another triassic form, associated at Diegerloch 
 with Microlestes. 
 
 Previous to this discovery of Professor Plieninger, the mat ancient 
 of known fossil Mammalia were those of the Stonesfield slate, above de- 
 scribed, p. 310, no representation 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 over- 
 spread with alluvium, derived from the disintegration of those rocks ; and 
 the mass of detritus is stained by oxide of iron, of precisely the same color 
 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 
 undistinguishable. The pebbles of gneiss in the Eocene red sandstone of 
 Auvergne point clearly to the rocks from which it has been derived. The 
 red coloring matter may, as in the Grampians, have been furnished by the 
 
CH. XXII] AND ROCK SALT. 343 
 
 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 on which this oxide of 
 iron abounds ; and when we find fossils in the New or Old Eed Sand- 
 stone in England, it is in the gray, and usually calcareous beds that 
 they occur. 
 
 The gypsum and saline matter, occasionally interstratified with such 
 red clays and sandstones of various ages, primary, secondary, and ter- 
 tiary, have been thought by some geologists to be of volcanic origin. 
 Submarine and subaerial exhalations often occur in regions of earth- 
 quakes and volcanoes far from points of actual eruption, and charged 
 with sulphur, sulphuric salts, and with common salt and 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 volcanoes, 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 intensely 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 hypothesis 
 advanced on the subject ; namely, that which attributes the precipitation 
 of the salt to evaporation, whether of inland lakes or of lagoons com- 
 municating 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 southwest, 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 tian 1700 feet. Ripple-marked sandstones, and the 
 footprints of animais, before described, are observed at so many levels 
 that we may safely assume the whole area to have undergone a slow and 
 gradual depression during the formation of the Rd Sandstone. The evi- 
 dence of such a movement, wholly independent of the presence of salt 
 itself, is very important in reference to the theory under consideration. 
 
 In the "Principles of Geology" (chap. 27), I published a map, fur- 
 
 * Ormerod, Quart Geol. Journ. 1848, vol. iv. p. 277. 
 
344 RUNN OF CUTC1I. [On. XXII 
 
 nished 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 Ire- 
 land. 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 incrusted 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 directions, the boundaries of the Runn have been enlarged by 
 subsidence. That successive layers of salt might be thrown down, one 
 upon the other, over thousands of square miles, in such a region, is un- 
 deniable. The supply of brine from the ocean would be as inexhausti- 
 ble as the supply of heat from the sun to cause evaporal'on. The only 
 assumption required to enable us to explain a great thickness 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 
 horizontal! ty. 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 suspen- 
 sion 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 accom- 
 panying 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 collected with shovels 
 into boats. The crystallization of the salt is effected by rapid evapora- 
 tion from the sun's heat and the supersaturation of the water with mu- 
 riate 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 re- 
 garded as a wide pan of enormous superficial extent, in which the brine 
 can easily reach the degree of concentration required." 
 
 Another traveller, Major Harris, in his " Highlands of Ethiopia," de- 
 scribes a salt lake, called the Bahr Assal, near the Abyssinian frontier, 
 which once formed the prolongation of the Gulf of Tadjara, but was 
 afterwards cut off from the gulf by a broad bar of lava or of land up- 
 raised 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 ellipti- 
 cal basin, seven miles in its transverse axis, half filled with smooth water, 
 of the deepest cerulean hue, and half with a solid sheet of glittering 
 
CH. XXII] SALTXESS OF THE KED SEA. 345 
 
 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 mollusks 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. G. 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 ^th P er cen *- ^^ e ^ e( ^ 
 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 burn- 
 ing 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 -5-^ th 
 part of its whole volume. The Red Sea, therefore, ought to have 1 per 
 cent, added annually to its saline contents ; and as these constitute 4 
 per cent, by weight, or 2J 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 under- 
 current 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 fram- 
 ing a true theory of the origin of rock-salt. 
 
 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 con- 
 
 * Hugh Miller, First Impressions of England, 1847, pp. 183, 214. 
 f Buist, Trans, of Bombay Geograph. Soc. 1850, vol. ix. p. 38. 
 
346 NEW BED SANDSTONE OF THE U. STATES. [Cn. XXII. 
 
 glomerate 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 neighborhood 
 of masses of trap which have been intruded into the red sandstone while 
 it was forming, or before the newer parts of vhe deposit had been com- 
 pleted. 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 Connecticut, and retain faithfully the im- 
 pressions 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 Prof. 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 skepticism is naturally entertained in regard to the 
 nature of the evidence derived from footprints, it may be well to enume- 
 rate some facts respecting them on which the faith of the geologist may 
 rest. When I visited the United States in 1842, more than 2000 im- 
 pressions 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 
 
 * Principles of Geol. 9th ed. p. 203. 
 f Travels m North America, vol. ii. p. 168. 
 J Hitchcock, Mem. of Amer. Acad. New Ser. vol. iii. p. 129. 
 See also Mem. Amer. Ac. vol. iii. 1848. 
 
CH. XXII.] 
 
 FOSSIL FOOT! BINTS IX CONNECTICUT. 
 
 347 
 
 on the lower surfaces or planes of the strata. If we follow a single line 
 of marks, we find them uniform in size, and nearlv 
 
 / 1^ 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 re- 
 lation between the distance separating two footprints 
 in one series and the size of the impressions ; in other 
 words, an obvious proportion between the length 01 
 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 ex- 
 ample, 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 liv- 
 ing 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 im- 
 pression of the terminal 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 continuous line of tracks the three-jointed and 
 ners in Faiis, a Valley of five-jointed toes placed alternately outwards, first on 
 Dr. ^eane^Mem^f the one side and ^^ n the other. In some speci- 
 Acad. vol. iv. me ns, besides impressions of the three toes in front, 
 the rudiment is seen of the fourth toe behind. It is 
 not often that the matrix has been fine enough to retain impressions of 
 the integument or skin of the foot ; but in one fine 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.* 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 sev- 
 eral laminae ; and if the upper layer originally 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 defined. 
 
 The size of several of the fossil impressions of the Connecticut red sand- 
 stone 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 
 
 * 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 
 gpecies. 
 
348 FOSSIL FOOTPKINTS IK THE [On. XXII. 
 
 other feathered giants of New Zealand were discovered. Their dimen- 
 sions have at least destroyed the force of this particular objection. The 
 magnitude of the impressions of the feet of a heavy animal, which has 
 walked on soft mud, increases for some distance below the surface origi- 
 nally 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 ^Epiornis, which has proba- 
 bly 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, Professor Owen does not believe thai the ^Epiornis 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 forwards. 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. Pro- 
 fessor 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 re- 
 marked 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 num- 
 ber 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 re- 
 ferring 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 coprolites ; 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 Ckeirotheria, and with a similar disproportion 
 between the hind and fore feet. Others resemble that remarkable rep- 
 tile, the Rhyncosaurus of the English Trias, a creature having some 
 
On. XXII] VALLEY OF THE CONNECTICUT. 349 
 
 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 Patago- 
 nia, swimming from island to island.* It is therefore 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 Con- 
 necticut. 
 
 To determine the exact age of the red sandstone and shale containing 
 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 de- 
 terminable 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 iti^s, strength, and tfrspov, a fin). They differ from Palceoniscus, 
 as Mr. Redfield first pointed out, by having the vertebral column pro- 
 longed 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. 330) as occurring near Rich- 
 mond 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 structure proves them 
 to be newer than the movements to which the Appalachian or AUeghany 
 chain owes its flexures, and this chain includes the ancient coal forma- 
 tion among its contorted rocks. The unconformable position of this New 
 Red with ornithicnites on the edges of the inclined primary or paleozoic 
 rocks of the Appalachians is seen at 4 of the section, fig. 505, p. 388. 
 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. 
 
 * Journal of Voyage of Beagle, Ac. 2d edition, p. 89, 1845. 
 
350 DIVISION OP THE PERMIAN GROUP. \Ga. XXIII 
 
 CHAPTER XXIII. 
 
 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 Sauriansof dolomitic conglomerate of Bristol Zechstein and Rothlie- 
 gendes of Thuringia Permian Flora Its generic affinity to the carboniferous 
 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 be- 
 tween 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 car- 
 boniferous 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 Magne- 
 sian Limestone division 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 Eng- 
 land, has given a table of the following six members of the Permian 
 system of the north of England, with what he conceives to be the corre- 
 sponding 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. Dolomit, or Upper Zechstein. 
 
 4. Compact limestone. 4, Zechstein, or Lower Zechstein. 
 
 6. Marl-slate. 5. Mergel-schiefer, or Kupferschiefer, 
 
 6. Inferior sandstones of various col- 6. Rothliegendes. 
 ors. 
 
 * Palseontographical Society, 1850,- London. 
 
CH. XXIII.] PERMIAN LIMESTONES. 351 
 
 I shall proceed, therefore, to treat briefly of these subdivisions, begin- 
 ning 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 Schlotheimi (fig, 
 444) and Mytilus septifer (fig. 446). 
 
 Fig. 444. Fig. 445. Fig. 446. 
 
 ScMzodn s Schlotheimi, Geinitz. The hinge of Schizodua Mytttu* 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 as- 
 sumes 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 con- 
 tains 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 mar- 
 ble to that of a cannon-ball, and radiating from the centre. ' Occasionally 
 earthy and pulverulent beds pass into compact limestone or hard granu- 
 lar 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 Eipon in 
 Yorkshire. 
 
 The brecciated limestone (No. 2) contains no fragments of foreign 
 rocks, but seems composed of the breaking-up of the Permian limestone 
 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 angu- 
 lar 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 
 
 * Trans. Geol. Soc. Lond. Second Series, vol. iii. p. 37. 
 
352 
 
 PERMIAN COMPACT LIMESTONES. 
 
 [Cfi. XXIII. 
 
 studying the phenomenon in the Marston Rocks, on the coast of Durham, 
 I found it impossible to form any positive opinion on the subject. The 
 well-known brecciated 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 variable species, and 
 
 Fig. 447. 
 
 I 
 
 a. Fenestella retiformis, Schlot. sp. 
 Syn. Gorgonia infundibuliformis, Goldf. : Reteporajlustracea, Phillips. 
 
 &. Part of the same highly magnified. 
 Magnesian limestone, Humbleton Hill, near Sunderland.* " $ 
 
 has received many different names. It sometimes attains a large size, measur- 
 ing 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 strata newer 
 than the Permian, are abundant in this division of the series in the ordinary 
 
 Fig. 448. Fig. 449. 
 
 Productus horridus, Sowerby 
 (including P. catous, Sow.) 
 Sunderland and Durham, in Magnesian 
 Limestone; Zechstein and Kupfer- 
 schiefer, Germany. 
 
 Spirifer undulatus, Sow. Min. Con. 
 Syn. Triogonotreta undulata, King's 
 
 Monogr. 
 Magnesiau Limestone. 
 
 yellow magnesian limestone. They are accompanied 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 
 lamellibranchiate 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. Beneath it 
 lies the marl-slate (No. 5), which consists of hard, calcareous 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 
 * King's Monograph, pi. 2. 
 
CH. XXIII.] FOSSIL FISH OF PERMIAN MARL-SLATE. 
 
 353 
 
 of fossil fish of the genera Palceoniscus, Pygopterus, Coelacanthus, and 
 Platysomus, genera which are all found in the coal-measures of the car- 
 boniferous 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. 
 
 Bestorcd outline of a fish of the genus Palceontecus, Agass. 
 Palceothrtesum, Blainville. 
 
 The Palceoniscus above mentioned belongs to that division of fishes 
 which M. Agassiz has called " Heterocercal," which have their tails une- 
 qually 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 8000 species at present 
 
 Fig. 451. 
 
 Fig. 452. 
 
 Shad, (dupea, Herring tribe.) 
 Homocercal. 
 
 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. 451.) 
 
 Now it is a singular fact, first pointed out by Agassiz, that the heter- 
 ocercal form, which is confined to a small number of genera in the exist- 
 ing 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 abore the 
 Magnesian limestone the homocercal tail predominates. 
 
 A full description has been given by Sir Philip Egerton of the species 
 of fish characteristic of the marl-slate in Prof. King's monograph before 
 referred to, where figures of the ichthyolites which are very entire and 
 well preserved, will be found. Even a single scale is usually so charac- 
 teristically marked as to indicate the genus, and sometimes even the par- 
 
 23 
 
354 
 
 DOLOMITIC CONaLOMEKATE. 
 
 [On. XXIII 
 
 ticular species. They are often scattered through the beds singly, and 
 may be useful to a geologist in determining the age of the rock. 
 
 Fig. 453. 
 
 Scales of fish. Maguesian limestone. 
 Fig. 451 Fig. 455. 
 
 Fig. 456. 
 
 Fig. 453. PalcEoniseus comptus, Agassiz. Scale magnified. Marl-slate. 
 
 Fig. 454. Palceoniscus elegans, Sedg. Under surface of scale magnified. Marl-slate. 
 
 Fig. 455. Palceoniscus glaphyrus, Ag. Under surface of scale magnified. Marl-slate. 
 
 Fig. 456. Goelacanthus granulatus, Ag. Granulated surface of scale magnified. Marl-slate. 
 
 Fig. 45T. 
 
 Fig. 458. 
 
 Pygopterus mandibularis, Ag. Marl-slate. 
 a. Outside of scale magnified. 
 &. Under surface of same. 
 
 Acrolepis Sedgwickii, Ag. 
 
 Outside of scale magnified. 
 Marl-slate. 
 
 The inferior sandstones (No. 6, Tab. p. 350), which lie beneath the 
 marl-slate, consist of sandstone and sand, separating the magnesian 
 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 geographical 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 Eussia, and of Colonel von Gutbier 
 in Saxony, to be, with few exceptions, distinct from that of the coal (see 
 p. 356). 
 
 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 
 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 irregulari- 
 ties in the mountain limestone, and being principally composed at every 
 
CH. XXIIL] THECODONT SAURIANS. 355 
 
 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 lime- 
 stone, recognizable by its peculiar shells and zoophites. 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 re- 
 mains of species of two genera have been found, called Thecodontosaurus 
 and Palceosaurus by Dr. Biley 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. 460. 
 
 Tooth of Palaeosaurus TO Tooth of Thecodontosaurus. 
 
 platyodon, nat size. TR 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 de- 
 termine 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 continue 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 P rotor osaur us, 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 
 white salt ; and of red and green grits, occasionally with copper ore ; also 
 magnesian limestones, marlstones, and conglomerates. 
 
 * Geol. Trans., Second Series, vol. v. p. 349, pi. 29, figures 2 and 5. 
 
 f Memoirs of Geol. Survey of Great Britain, vol. i. p. 268. 
 
 j Owen, Eeport on Reptiles, British Assoc., Eleventh Meeting, 1841, p. 197. 
 
 Russia and the Ural Mountains, 1845 ; and Siluria, ch. xii. 1854. 
 
356 PERMIAN FLOEA. [Co. XXIII 
 
 The country of Mansfeld, in Thuringia, may be called the classic 
 ground of the Lower New Ked, 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 lime- 
 stone, 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 Sandstone above mentioned, which occu- 
 pies a similar place in England between the marl-slate and coal. Its 
 local name of " Rothliegendes," red-Iyer, or " Roth-todt-liegendes," rcd- 
 dead-lyer, was given by the workmen in the German mines from its red 
 color, and because the copper has died out when they reach this rock, 
 which is not metalliferous. It is, in fact, a great deposit of red sand- 
 stone and conglomerate, 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 have not yet 
 
 Fig. 461. 
 
 Walchia piniformis, Sternb. Permian, Saxony. (Gutbier, pi. x.) 
 a. Branch. &. Twig of the same. c. Leaf magnified. 
 
 been found elsewhere. Two or three of .these, as Calamites gigas, Sphe- 
 nopteris erosa, and S. lobata, are also met with in the government oi 
 Perm in Russia. Seven others, and among them Neuropteris p 4g2 
 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 ny< 
 Saxony, Thuringia, and Russia, although not abundant. Noeggerathia 
 
Cn. XXIII] 
 
 PERMIAN FLORA. 
 
 357 
 
 Fig. 463. 
 
 (see fig. 463), supposed by A. Brongniart to be allied to Cycas, is another 
 
 link between the Permian and Carboniferous vegetation. Coniferse, 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 carboniferous period, are 
 
 as yet wanting. 
 
 Among the remarkable fossils of the rothlie- 
 gendes, 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 edition to the original 
 stem, so as to double or quadruple its diameter. 
 The same remark holds good in regard to certain 
 living extra-tropical arborescent ferns, particularly 
 those of New Zealand. 
 
 Psaronites are also found in the uppermost coal 
 of Autun in France, and in the upper coal-meas- 
 ures of the State of Ohio in the United States, but 
 specifically different from those of the rothlie- 
 gendes. 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 tri- 
 assic ; and the same may be said of the Permian fauna. 
 
 * Murchison's Russia, voL ii. pi. A, fig. 8. 
 
 Noeggerafhia cuneifolia. 
 Ad. Brongniart.* 
 
358 ' THE CARBONIFEROUS GROUP. [Cn. XXIV 
 
 CHAPTER XXIV. 
 
 THE COAL, OR CARBONIFEROUS GROUP. 
 
 Carboniferous strata in the southwest of England' Superposition of Coal-measures 
 to Mountain limestone Departure from this type in North of England and 
 Scotland Carboniferous series in Ireland Sections in South Wales Under- 
 clays with Stigmaria Carboniferous Flora Ferns, Lepidodendra, Equisetacese, 
 Calamites, Asterophyllites, Sigillarise, Stigmarice Coniferse Sternbergia 
 Trigonocarpon Grade of Coniferse in the Vegetable Kingdom Absence ot 
 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 accumula- 
 tion of the Coal-measures Brackish- water and marine strata Crustaceans ot 
 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 Professor Phil- 
 lips 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 different 
 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 Carboniferous Limestone, of purely 
 marine origin, and containing corals, shells, and encrinites. 
 
 In the Southwestern part of our island, in Somersetshire and South 
 Wales, the three divisions usually spoken of by English geologists are : 
 
 , n -, ( Strata of shale, sandstone, and grit, with occasional seams 
 
 J I of coal, from 600 to 12,000 feet thick. 
 
 iA coarse quartzose sandstone passing into a conglomerate, 
 sometimes used for millstones, with beds of shale ; usually 
 devoid of coal ; occasionally above 600 feet thick. 
 
 n K % n (. A calcareous rock containing marine shells and corals ; de- 
 
 limVstone \ void 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 some bands 
 
CH. XXIV.] COAL-MEASURES. 359 
 
 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 Mountain Limestone. The latter is 
 found in the southern British coal-fields, at the base of the system, or 
 immediately in contact with the subjacent 6ld Red Sandstone ; but as we 
 proceed northwards to Yorkshire and Northumberland it begins to alter- 
 nate 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 
 Fifeshire 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 contain- 
 ing 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 Yel- 
 ow Sands*one, 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 .... IQOO 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, <fec.) 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 perhaps 
 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 be- 
 neath fresh or salt water should the ground sink vertically a few feet 
 
 In one section near Swansea, in South Wales, where the total thick- 
 ness of strata is 3246 feet, we learn from Sir H. De la Beche that there 
 are ten principal masses of sandstone. One of these is 500 feet thick, 
 
 * Sedgwick, Geol. Trans., Second Series, vol. iv.; and Phillips, GeoL of Yorsh. 
 part 2. 
 
CARBONIFEROUS FLOKA. [Ca. XXIV. 
 
 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 pre- 
 dominate over the sandstones. The horizontal extent of some seams of 
 coal is much greater than that of others, but they all present one charac- 
 teristic feature, in having, each of them, what is called its underclay. 
 These underclays, coextensive with every layer of coal, consist of arena- 
 ceous 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 essential 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 carbonaceous 
 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 Stig- 
 marice, 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 directions. 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 enveloped 
 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 understand 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 pro- 
 duce coal, it will be necessary to offer a brief preliminary 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 remarked that Goppert has ascer- 
 tained 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 geological interest attached to this flora. 
 
 Ferns. The number of species of carboniferous plants hitherto de- 
 scribed amounts, according to M. Ad. Brongniart, to about 500. These 
 * Memoirs of Geol. Survey, vol. i. p. 1-J5. 
 
CH. XXIV.] FERNS OF CARBONIFEROUS PERIOD. 
 
 361 
 
 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 
 
 Fig. 464 
 
 Fig. 465. 
 
 Pecopteris lonchitica. 
 (Foss. Flo. 153.) 
 
 a. SpTienopteris crenata. 
 &. Part of the same, magnified. 
 (Fosa. Flo. 101.) 
 
 Fig. 466. 
 
 of almost all the other fossils except the co- 
 niferae. 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 contemporary tribes, with the excep- 
 tion of the coniferse, 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 fruc- 
 tification, but in some specimens these are 
 well preserved. In the general absence of 
 such characters, they have been divided into 
 genera distinguished chiefly 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 Eu- 
 ropean ferns, but some were decidedly arborescent, especially the group 
 
 Caulopteris primwca, Lindley. 
 
362 FERNS LEPIDODENDRON. [Cii. XXIV, 
 
 called Caulopteris, by Lindley, and the Psaronius of the upper or newest 
 coal measures, before alluded to (p. 357). 
 
 All the recent tree-ferns belong to one tribe (Polypodiacece\ and to ? 
 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 mis- 
 taken, in the absence of their fructification, 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 di- 
 chotomous (see fig. 471). They are considered by Brongniart and Hooker 
 to belong to the Lycopodiacece, 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 some- 
 times 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). 
 
LEPIDODENDRON. 
 
 Fig. 4T1. 
 
 363 
 
 Lepidodendron Sternbergii, Coal-measures, near Newcastle. 
 
 Fig. 4TO. Branching trunk, 49 feet long, supposed to have belonged to L. Stern- 
 
 lergii. (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.) 
 
 Fig. 473. 
 
 a. Lycopodium densum ; banks of E. Thames, New Zealand. 
 6. Branch, natural sue. 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 Lepidostro 
 bus by M. Adolphe Brongniart, are met with. (See fig. 474.) They 
 often form the nucleus of concretionary balls of clay-ironstone, and are 
 
 Fig. 474 
 
 a. Lepidoitrdbus ornatvA, Brong. Shropshire ; half natural size. 
 
 &. 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. it part 
 
 2, p. 440.) 
 
 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 Lepidostrobus is the fruit of Lepidoden- 
 
364: 
 
 EQUISETACE^ CALAMITES. 
 
 [On. XXIV. 
 
 dron ; indeed, it is not uncommon in Coalbrook Dale, and elsewhere, to 
 find these strobili or fruits terminating the tip of a branch of a well char 
 acterized Lepidodendron. 
 
 Equisetacece. To this family belong two fossil species of the Coal 
 one called Equisetum infundibuliforme by Brongniart, and found also in 
 jSTova Scotia, which has sheaths, regularly toothed, ribbed, and overlap- 
 ping like those on the young fertile stems of Equisetum fluviatile. It 
 was much larger than any living "Horsetail." The Equise turn giganteum, 
 discovered by Humboldt and Bonpland in South America, attained a 
 height of about 5 feet, the stern 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. 4T5. 
 
 Fig. 476. 
 
 Calamites cannoeformis, Schlot 
 (Foss. Flo. 79.) Common in 
 English coal. 
 
 Calamites Suckowii, Brong. ; 
 natural size. Common in 
 coal throughout Europe. 
 
 Fig. 477. 
 
 for, like the common " horsetail," they usually exhibit 
 little more than hollow jointed stems, furrowed ex- 
 ternally. (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 inter- 
 node.* The specimen, fig. 475, therefore, is no doubt 
 the lower end of the plant, and I have therefore re- 
 versed 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 
 
 * See Dawson, Geol. Quart. Journal, 1854, vol. x. p. 35. 
 
 Eadical termination of 
 Scotia. 
 
CH. XXIV.] 
 
 CALAMITES. 
 
 365 
 
 Fig. 478. 
 
 Calamites cannot belong to the Equiseta, nor probably to any tribe of 
 flowerless plants. He conceives that they are more nearly allied to the 
 Gymnospennous Dycotyledons. They possessed a central pith, surround- 
 ed 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 exter- 
 nally, its pith being articulated and marked with deep external vertical 
 stria?, 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 sin- 
 gular fossil. Their views have been 
 confirmed by Prof. Williamson of 
 Manchester, who has communicated 
 to me a specimen, figured in the 
 annexed cut (fig. 478), in which 
 we see an internal pith answering 
 in character to the Calamodendron, 
 and yet having outside of it another 
 jointed cylinder vertically grooved 
 on its outer surface, so that in the 
 same stem we have one calamite 
 enveloping another. Yet that they 
 both formed part of the same plant, 
 is proved by the following circum- 
 stances : 1st. Near each articula- 
 tion of the pith, radiating spokes 
 
 Portion of a Calamite, near the base, showing the -. A 
 
 external cylinder, connected by radiating vessels ^6 seen tO proceed ana penetrate 
 
 ^to&ft^SS^'**** ligneous zone. One complete 
 
 Communicated by ProtW.C. Williamson. ^^ Qr circ ] e Q f fo esQ ra( jjj j s 
 
 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 beforementioned and by 
 the medullary rays, is usually reduced to brown carbonaceous matter, 
 preserving merely a tendency to break in longitudinal 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. 
 
366 ASTEKOPHYLLITES SIGILLAKIA. [On. XXIV. 
 
 In conclusion, I may remark, that these discoveries make it more and 
 more doubtful to what family the greater number of Calamites should be 
 referred. Their internal organization, says Prof. Williamson, was very 
 peculiar; for, while they exhibit remarkable affinities with gymno- 
 spermous dicotyledons, the arrangement of their tissues differs widely from 
 that of all known forms of gymnosperms. 
 
 Asterophyllites. The graceful plant represented in the annexed figure, 
 is supposed by M. Brongniart to be a branch of the Calamodendron, 
 and he infers from its pith and medullary rays that it was dicotyledonous. 
 It appears to have been allied, by the nature of its tissue, to the gym- 
 Fig. 479. 
 
 AsterophylUtesfoliosa. (Foss. Flo. 25.) Coal-measures, Newcastle. 
 
 nogens, and to Sigillaria. But under the head of Asterophyllites many 
 vegetable fragments have been grouped which probably belong to differ- 
 ent genera. They have, in short, no character in common, except that 
 of possessing narrow, verticillate, one-ribbed leaves. Dr. ISTewberry, of 
 Ohio, has discovered in the coal of that country fossil stems which in 
 their upper part bear wedge-shaped leaves corresponding to Spheno- 
 phyllum, while below the leaves are stalk-like and capillary, and would 
 have been called Asterophyllites if found detached. From this he infers 
 that Sphenophyllum 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 peculiar, and, with 
 reference to existing types, very anomalous. They were formerly refer- 
 red, by M. Ad. Brongniart, to ferns, which they resemble in the scala- 
 riform texture of their vessels, and, in some degree, in the form of the 
 
 * Annals of Science, Cleveland, Ohio, 1853, p. 97. 
 
Cn. XXIV.] 
 
 SIGILLARIA AND STIGMARIA. 
 
 367 
 
 cicatrices left by the base of the leaf-stalks which have fallen off (see 
 fig. 480). But with* these points of analogy to cryptogamia, they corn- 
 Fig. 480. Dme an internal organization much resembling 
 that of Sycads, and some of them are ascer- 
 tained to have had long linear leaves, quite 
 unlike those of ferns. They grow to a great 
 height, from 30 to 60, or even 70 feet, with 
 regular cylindrical stems, and without branch- 
 es, although 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 
 converted into bright shining coal) to consti- 
 tute 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 uncompressed, 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 flowerless 
 plants now living. The scalariform structure of their vessels agrees pre- 
 cisely 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. 
 Kichard Brown, in his description of the Stigmarice occurring in the 
 
 Fig. 481. 
 
 Sigillaria l&vigata, Brong. 
 
 Stigmaria attached to a trunk of Sigillaria.* 
 
 * The trunk in this case is referred by Mr. Brown to Lepidodendron, but his 
 illustrations seem to show the usual markings assumed by Sigillaria near its 
 base. 
 
368 CONIFERS OF THE COAL PERIOD. [On. XXIV. 
 
 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 root- 
 lets, in all directions, into the surrounding clay. 
 
 In the sea-cliffs of the South Joggins in Nova Scotia I examined sev- 
 eral erect Sigtilarias, in company with Mr. Dawson, and we found that 
 from the lower extremities of the trunk they sent out Stigmarice 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 concave, and fitting 
 on to a tubercle (see figs. 482 and 483). Rows of these tubercles are 
 
 Fig. 483. 
 Fig. 4821 
 
 Surface of another individual 
 of same epecies, showing 
 form of tubercles. (Foss. 
 Flo. 84.) 
 
 Stigmaria ficoides, Brong. One-fourth of nat. size. (Foss. Flo. 32.) 
 
 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. 
 
 Coniferce. The coniferous trees of this period are referred to five gen- 
 era ; 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 Coniferce, in having 
 large piths ; for Professor Williamson has demonstrated the fossil of the 
 coal-measures called Sternlergia to be the pith of these trees, or rather 
 the cast of cavities formed by the sinking 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 com- 
 mon Walnut and the White Jasmine, in which the pith becomes so re- 
 duced as simply to form a thin lining of the medullary cavity, across 
 which transverse plates of pith extend horizontally, so as to divide the 
 cylindrical 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 Sterribergia (d, d, 
 fig. 484) was given. 
 
Cn. XXIV.] CONIFERS OF THE COAL PERIOD. 
 
 Fig. 484 
 
 369 
 
 Fig. 484. Fragment of coniferous wood, Dadoxylon, 
 Endlicher, fractured longitudinally; from Coal- 
 brook Dale. W. C. Williamson,* 
 
 a. Bark. 
 
 6. Woody zone or fibre (pleurenchyma). 
 
 c. Medulla or pith. 
 
 d. Cast of hollow pith, or " Sternhergia." 
 
 Magnified portion of fig. 484; transverse section. 
 c. Pith. Z>, &. Woody fibre. <?, e. Medullary rays. 
 
 In the above specimen the structure of the wood (6, 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 supposed 
 
 Fig. 487. 
 
 Fig 486. 
 
 Trigonocarpum ovatum, Lindley & Hutton. 
 Peel Quarry, Lancashire. 
 
 Trigonocarpum olwceforme, Lindley, 
 with its fleshy envelope. Felling 
 Colliery, Newcastle. 
 
 to be the fruit of a palm, may now, according to Dr. Hooker, be referred 
 like the Sternbergia, to the Coniferce. Its geological 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 
 nart of the formation where they do not occur, except the underclays and 
 
 * Manchester Philos. Mem. vol. ix. 1851. 
 24 
 
370 GRADE OF THE CARBONIFEROUS FLORA. [Cn. XXIV 
 
 limestone. The sandstone, ironstone, shales, and coal itself, all contair 
 them. Mr. Binney has at length found in the clay-ironstone of Lanca- 
 shire several specimens displaying structure, and from these, says Dr, 
 Hooker, \ve 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- 
 tmt. 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, exhibiting exten- 
 sive modifications of elementary organs for the purpose of their adaptation 
 to special functions, and these modifications are as great, and the adapta- 
 tion as special, as any to be found amongst analogous fruits in the ex- 
 isting vegetable world."* Professor Williamson, in his paper on Stern- 
 lergia, has likewise remarked 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 de- 
 serve notice, because a question has arisen whether the Coniferce 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 Gymno- 
 sperms are not inferior in rank, having every typical character 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 impregnation, so that this character cannot be relied on 
 as constituting a fundamental difference in structural development. The 
 Coniferae are exogenous, and have the same distinctions of pith, wood, 
 bark, and medullary rays as have the angiospermous trees. Whether 
 the woody fibre with disks characteristic of Coniferse be a more or a 
 less complex tissue than the spiral vessels, is a controverted point. As 
 he spiral vessels occur in the young shoots, and are lost in the mature 
 
 * Proceedings of the Royal Society, vol. vii. March, 1854, p. 28. 
 
CH. XXIV.] GEADE OF THE CARBONIFEROUS FLORA. 371 
 
 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 ambi- 
 guity 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 func- 
 tional importance, even where the function is clearly ascertained. It is 
 enough for the geologist to know, that fossil Coniferse 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 char- 
 acterizing the carboniferous flora as consisting of imperfectly developed 
 plants. 
 
 Although our data are confessedly too defective to entitle us to gen- 
 eralize 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 Dicotyle- 
 donous Angiosperms seems clear, and the abundance of Ferns and Lyco- 
 pods may justify Adolphe Brongniart in calling the primary periods the 
 age of Acrogens.* (" Le regne des Acrogens.") As to the Sigillariae 
 and Calamites, they seem to have been distinct from all tribes of now- 
 existing plants. That the abundance of ferns implies a moist atmo- 
 sphere, 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 Coniferae attain their maximum in 
 numbers, constituting -g^d part of all the flowering plants ; whereas 
 in a wide district around the Cape of Good Hope they do not form 
 j-^o oth of the phenogamic flora. Besides the conifers, many species of 
 ferns flourish in New Zealand, some of them arborescent, together with 
 many lycopodiums ; so that a forest in that country may make a nearer 
 approach to the carboniferous vegetation than any other now existing on 
 the globe. 
 
 Angiosperms. Some of the grass-like leaves Fig. 488. 
 
 termed Poacites, having fine longitudinal striae, are 
 conjectured to belong to Monocotyledons; but the 
 determination is doubtful, as some of them may be 
 the leaves of Lepidodvndra, 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 bursting. He suggests that they 
 may be coniferous, although he cannot connect them 
 with any known fossil conifer. 
 
 * For terminology of classification of plants, see above, note, p. 265. 
 
372 COAL EKECT FOSSIL TEEES. [On. XXIV. 
 
 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 Gb'ppert, 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 abun- 
 dance, as to appear to form the bulk of the coal. In some places, almost 
 all the plants were calamities, in others ferns.* " Some of the plants of 
 our coal," says Dr. Buckland, " grew on the identical 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, particularly 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 sev- 
 eral 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 rail- 
 way. 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 im- 
 bedded 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 nod- 
 ules 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. 363). 
 The exterior trunk of each was marked by a coating of friable coal, va- 
 rying 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 15g feet in circumference at the base, 7 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 through- 
 out ; for solid dicotyledonous trees, when prostrated in tropical forests, 
 as in Venezuela, 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., p. 17. 
 f Anniv. Address to Geol. Soc., 1840. 
 
Cu. XXIV.] COAL ERECT FOSSIL TREES. 373 
 
 most rapidly in low and flat tracks, 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 vege- 
 tation 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 re- 
 tained 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 imbedded 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 hor- 
 izontal. Here it was distended laterally, and flattened so as to be only 
 one inch thick, the flutings being comparatively 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 beau- 
 tifully 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 sand- 
 stone, and increasing gradually in size towards the base, and being with- 
 out 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 external layer is overcome, the 
 heavy column falls suddenly in a perpendicular or oblique direction from 
 the roof of the gallery whence coal has been extracted, wounding or kill- 
 ing the workman who stands below. It is strange to reflect how many 
 thousands of these trees fell originally in their native forests in obe- 
 dience to the law of gravity ; and how the few which continued to stand 
 erect, obeying, after myriads of ages, the same force, are cast down to 
 immolate their human victims. 
 
 * Hawkshaw, Geol Trans., Second Series, voL vl pp. 173, 177, pL 17. 
 f GeoL Report on Cornwall, Devon, and Somerset, p. 143. 
 j Lindley and Hutton, Foss. Flo. part 6, p. 150. 
 
374 
 
 PAEKFIELD COLLIEKY. 
 
 [On. XXIV 
 
 Fig. 4S9. 
 
 Ground-plan of a fossil forest, Parkfield Colliery, near 
 Wolverhampton, showing the position of 73 trees in 
 a quarter of an acre.* 
 
 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 ex- 
 pose 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 Col- 
 liery, near Wolverhamp- 
 
 ton. 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 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 meas- 
 ured 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 distinct horizontal strata 
 of micaceous sandstone are traversed by vertical trunks of monocotyledonous 
 vegetables, resembling bamboos or large Equiseta (fig. 490). Since the con- 
 solidation 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 monu- 
 ments of a submerged forest. I formerly objected to this conclusion, 
 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 inclosed. 
 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. Brongniart's view was correct. These plants seem 
 to have grown on a sandy soil, liable to be flooded from time to time f 
 
 * Messrs. Beckett and Ick. Proceed. Geol. Soc. vol. iv. p. 287. 
 f Annales des Mines, 1821. 
 
CH. XXIV.] 
 
 COAL ERECT FOSSIL TREES. 
 Fig. 490. 
 
 375 
 
 Section showing the erect position of fossil trees in coal sandstone at 
 St Etienne. (Alex. Brongniart) 
 
 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 diam- 
 eter 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 con- 
 verted into a thin coating of the 
 purest and finest coal, forming a 
 striking contrast in color with the 
 white quartzose sandstone in which 
 it lay. The annexed figure repre- 
 sents a portion of this tree, about 
 to' & E 2 d 7o burgh ' An s leofinclinationfronia 15 feet long, which I saw exposed 
 
 Fig. 491. 
 
 * Prlhciples of Geol. 9th ed. p. 268. 
 
376 
 
 COAL OBLIQUE FOSSIL TKEES. 
 
 [Cn. XXIV. 
 
 in 1830, when all the strata had been removed from one side. The 
 beds which remained were so unaltered and undisturbed at the point of 
 junction, as clearly to show that they had been tranquilly deposited 
 round 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, calca- 
 reous.* 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 do wnwards,the roots of all, save one, 
 rubbed off by attrition. One of these was 60 and an- 
 other 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 accumu- 
 lation 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 succession 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, bor- 
 dering the Chignecto Channel, a branch of the Bay of 
 Fundy, in Nova Scotia.f 
 
 * See figures of texture, "Witbam, Foss. Veget. pi. 3. 
 f See Lyell's Travels in N. America, vol. ii. p. 179 ; and.Dawson, Geol. Journ. No. 87 
 
 
 * 
 
CH. XXIV.] COAL FOSSIL FORESTS IX XOVA SCOTIA. 377 
 
 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 
 inclination 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 
 observed seventeen trees in an upright position, or, to speak more cor- 
 rectly, 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 same beds is exposed to view on the 
 beach. The thickness of the beds alluded to, between d and g, is about 
 2500 feet, the erect trees consisting chiefly of large Sigillarice, occurring 
 at ten distinct levels, one above the other ; but Mr. Logan, who after- 
 wards made a more detailed survey of the same line of cliffs, found erect 
 trees at seventeen levels, extending through a vertical thickness of 4515 
 feet of strata ; and he estimated the total thickness of the carboniferous 
 formation, with and without coal, at no less than 14,570 feet, everywhere 
 devoid of marine organic remains.* The usual height of the buried 
 trees seen by me was from 6 to 8 feet ; but one trunk was about 25 feet 
 high and 4 feet in diameter, with a considerable bulge at the base. In 
 no instance could I detect any trunk intersecting a layer of coal, how- 
 ever 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. Originally the re- 
 verse 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 effec- 
 tually the undermining power of the river, or of the sea at the base of 
 the delta, than do beds of loose sand or layers of mud not supporting 
 trees. 
 
 This fact may explain why seams of coal have so often escaped denu- 
 dation, 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 re- 
 moved. 
 
 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 Stigmaria, which had 
 
 * Quart. GeoL Journ. voL ii. p. 177. 
 
378 
 
 COAL FOSSIL FOKESTS IN NOVA SCOTIA. [Cn. XXIV. 
 
 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, 6, 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, tra- 
 versing various strata, and cut off at the top by a layer of clay 2 feet thick 
 
 Fossil tree at right angles to planes of stratification. 
 Coal measures, Nova Scotia. 
 
 Pig. 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 d), while at a greater height the trees 
 / and g rest upon a thin seam of coal (e), and above them is an under- 
 day, supporting the 4-foot coal. 
 
 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) 1 foot 
 thick, and above this clay (e) 2 feet 8 inches. But, in the interior, were 
 nine distinct layers of different composition : 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 of ironstone 2 inches, 
 then pure clay 2 feet, then sandstone 3 inches, and lastly, clay 4 inches. 
 
CH. XXIV.] COAL FOSSIL FORESTS OF NOVA SCOTIA. 379 
 
 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 correspondence 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 sigilla- 
 rian trunks support at different levels roots and stems of Calamites ; the 
 Calamites having begun to grow after the older Sigillarice had been par- 
 tially 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 de- 
 cayed and gone. In such cases the submerged portion is sometimes 
 found filled with mud. 
 
 One of the erect fossil trees of the South Joggins has been shown by 
 Mr. Dawson to have Araucarinn structure, so that some Coniferce 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 spe- 
 cies of Spirorbis or Serpula (fig. 498) attached itself to the outside 
 of the stumps and stems of the erect trees, adhering occasionally 
 even to the interior of the bark, another proof that the process of 
 envelopment was very gradual. These hollow upright trees, covered 
 with 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 
 
380 COAL FOSSIL FORESTS OF NOVA SCOTIA. [Cn. XXIV. 
 
 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 eveiy 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 inter- 
 secting 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. 
 He 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. 378) consisting of Cypris, Unio (?), Modiola, and an annelid proba- 
 bly 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 up- 
 right 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. Accordingly rain-prints 
 were seen by me and Mr. Dawson d: various levels, but the most perfect 
 hitherto observed were discovered by Mr. Brown near Sydney in Cape 
 Breton. They consist of very delicate impressions of rain-drops on green- 
 ish slates, with several worm-tracks (a, &, fig. 495), such as usually accom- 
 pany rain-marks on the recent mud of the Bay of Fundy, and other 
 modern beaches. 
 
 The casts of rain-prints, in figs. 496 and 491, 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 sandstone 
 presenting a similar warty or blistered surface, on which are also 
 
 * Geol. Quart. Journ. vol. ii. p. 393; and vol. vi. p. 115. 
 
CH. XXIV.] COAL RAIN-PRINTS. 
 
 Fig. 495. 
 
 381 
 
 FK 495. Carboniferous rain-prints with worm-tracks (a, b) on green shale, from Cape 
 
 Breton, Nova Scotia. Natural size. 
 
 Fig. 496. Casts of rain-prints on a portion of the same slab, fig. 495, seen on the under 
 
 side of an incumbent layer of arenaceous shale. Natural #ize. 
 
 The arrow represents the supposed direction of the shower. 
 
 observable some small ridges as at a, which stand out in relief, and 
 afford evidence of cracks formed by the shrinkage of subjacent clay, on 
 
 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 size. 
 
 which rain had fallen. Many of the associated sandstones are ripple- 
 marked. 
 
 The great humidity of the climate of the coal period had been pre- 
 viously inferred from the nature of its vegetation and the continuity of 
 its forests for hundreds of miles ; but it is satisfactory to have at length 
 obtained such positive proofs of showers of rain, the drops of which 
 resembled in their average size those which now fall from the clouds. 
 From such data we may presume that the atmosphere of the carbo- 
 niferous period corresponded in density with that now investing the 
 globe, and that different currents of air varied then as now in tempera- 
 
382 PURITY OF THE COAL. [On. XXiV. 
 
 ture, so as to give rise, by their mixture, to the condensation of aqueous 
 vapor. 
 
 The more closely the strata productive of coal have been studied 
 the greater has become the force of the evidence in favor 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 parti- 
 cles 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 particles 
 and sand, throughout areas of vast extent, is a fact which appears very 
 difficult to explain when we attribute each coal-seam to a vegetation 
 growing in swamps. It has been asked how, during river inundations, 
 capable of sweeping away the leaves of ferns and the stems and roots of 
 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 afterwards covered with mud since 
 turned to shale. Yet the coal itself or altered vegetable matter remained 
 all the while unsoiled by earthy particles. This enigma, however per- 
 plexing 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 favorable. There is no pos- 
 sibility 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 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 
 
CH. XXIV.] LONG PERIODS OF ACCUMULATION. 383 
 
 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 dtstichum), 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- 
 njeasures 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 ^ye take the 
 average thickness of the beds at 7500 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 Brunswick 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 7500 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 ba as calculated by Mr. Forshey, 450,000 cubic feet per second, 
 througnout 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 an- 
 nually 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 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, resem- 
 bling that now experienced in certain countries, where, whether the 
 
 * Lyell's Second Visit to the U. S., vol. ii. p. 245 ; and American Journ. of 
 Science, 2d series, vol. v. p. 17. 
 
 f Principles of Geology, 9th ed. 1853, p. 273. 
 j Ibid. 1853, p. 283. 
 
384: BRACKISH-WATER AND MARINE STRATA. [On. XXIV. 
 
 movement be upward or downward, it is quite insensible to the inhabi- 
 tants, and only known by scientific inquiry. If, on the other hand, it 
 was brought about in two millions of years according to the other stan- 
 dard 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 under- 
 ground ; 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 con- 
 tained 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 recognized. 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 carbo- 
 niferous 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 resembles some lacustrine limestones of France and Ger 
 many. It has been traced for 30 miles in a straight line, and can be 
 recognized at still more distant points. The characteristic fossils are a 
 small bivalve, having the form of a Cyclas or Cyrena, also a small ento- 
 mostracan which may be a Cyprif, or, if marine, a Cythere (fig. 499), 
 and the microscopic shell of an annelid of an extinct genus called Micro- 
 conchus (fig. 498), allied to Serpula or Spirorlis. 
 
 Fig. 498. Fig. 499. 
 
 a. Microconchus (Spirorlis) Cypris f inflate (or Cythere f). 
 
 carbonarius. Nat size, Nat. size, and magnified. 
 
 and magnified. Murchison,* 
 
 Z>. var. of same. 
 
 * Silurian System, p. 84. 
 
CH. XXIV.] 
 
 CKUSTACEANS OF THE COAL. 
 
 385 
 
 Fig. 500. 
 
 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 intc 
 sandstone. The coal-seams often wedge out or disappear ; and sections, 
 at places nearly contiguous, present marked lithological distinctions. 
 Tn this single field, in which the strata are from TOO to 800 feet thick, 
 between forty and fifty species of terrestrial plants have been discovered, 
 besides several fishes of the genera Megalichthys, 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 Limulus rotundatu*, Prestwich. 
 
 -o v . T . T Coal, Coa.brook Dale. 
 
 that ot the living Limulus. 
 
 The perfect carapace of a long-tailed or decapod crustacean ha* 
 also been found in the iron-stone 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 freshwater 
 shells with others full of marine remains, 
 and the alternation of coarse sandstone and 
 conglomerate with beds of fine clay or shale 
 containing the remains of plants, may be ex- Glyp1ieaf duMa , Saltcr . 
 plained by supposing the deposit of Coalbrook Syn. Apus duUm, Milne Edward?. 
 
 _' rr . The oldest recorded decapod (or 
 
 Dale to have originated m a bay of the sea or long-tailed) crustacean. Cosi- 
 
 . , -i-r/i 3 - j ri measures, Coalbrook Dale. 
 
 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 cock- 
 roach or Blatta family, and the wing of a cricket (Acridites), have been 
 described by Germar.f 
 
 Fig. 501. 
 
 * Prestwich, GeoL Trans., 2d series, voL v. p. 440. 
 f See Munster's Beitr. voL v. pi. 13, 1842. 
 25 
 
386 
 
 CLAY-IRON-STONE. 
 
 [On. XXIV 
 
 More recently (1854) Mr. Fr. Goldenberg has published descriptions 
 of no less than twelve species of insects from the nodular clay-iron-stone 
 of Saarbruck near Treves.* They are associated with the leaves and 
 branches of fossil ferns. Among them are several Blattinci, three species 
 of Neuroptera, one beetle of the Scarabceus family, a grasshopper or 
 locust, Gryllacris (see fig. 502), and several white ants or Termites. 
 
 Fig. 502. 
 
 Wing of a Grasshopper. 
 
 GryUacris lithanthraca, Goldenberg. 
 
 Coal, Saarbruck near Treves. 
 
 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 Listen (fig. 503), Orthoceras, and Avicula 
 papyracea, Goldf. (fig. 504). 
 
 Fig. 503. 
 
 Fig. &U4. 
 
 Goniatites Listeri, Martin, sp. 
 
 A vicula pap yracea, Goldf. 
 (Pecten papyraceus, Sow.) 
 
 No similarly intercalated layer of marine shells has been noticed in 
 the neighboring coal-field of Newcastle, where, as in South Wales and 
 
 * Palceont. Bunker and V. Meyer, vol. iv. p. 17. 
 
CH. XXV.] COAL-FIELDS OF UNITED STATES. 387 
 
 Somersetshire, the marine deposits are entirely below those containing 
 terrestrial and freshwater remains.* 
 
 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 carbonate 
 of iron, mingled mechanically with earthy matter, like that constituting 
 the shales. Mr. Hunt, of the Museum of Practical Geology, instituted 
 a series of experiments to illustrate the production 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 peroxide into protoxide by taking a portion 
 of its oxygen to form carbonic acid. Such carbonic acid, meeting with 
 the protoxide of iron in solution, would unite with it and form a car- 
 bonate 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.f 
 
 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 
 Alleghanies 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 carbo- 
 niferous period Insects in coal Rarity of air-breathing animals Great num- 
 ber of fossil fish First discovery of the skeletons of fossil reptiles Footprints 
 of reptilians First land-shell found Rarity of air-breathers, whether verte- 
 brate 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 independent 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 carboniferous 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 moun 
 tains. 
 
 The annexed diagram (fig. 505) will assist the reader in under- 
 
 * Phillips ; art, " Geology," Encyc. Metrop. p. 592. 
 f Memoirs of Geol. Survey, pp. 51, 255, <fec. 
 
388 GEOLOGICAL STKUCTUKE OF UNITED STATES. [On. XXV 
 
 T-' <N cc -* 
 
CH. XXV.] CARBONIFEROUS GROUP. 389 
 
 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. 180, 231, and 254), 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. 346). 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 "Atlantic Slope," corresponds 
 nearly in average width with the low and flat plain (A B), and is charac- 
 terized by hills of moderate height, contrasting strongly, in their rounded 
 shape and altitude, with the long, 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 
 colors, running 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 mentioned, 
 consist of strata, folded into a succession of convex and concave flexures, 
 subsequently laid open by denudation. The component 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 system of hills extends, geologically considered, from Vermont to 
 Alabama, being more than 1000 miles long, from 50 to 150 miles broad, 
 and varying in height from 2000 to 6000 feet. Sometimes the whole 
 assemblage 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 Pennsylvania, 
 Prof. W. B. Rogers and his brother Prof. H. D. Rogers, for the import- 
 ant discovery of a clue to the general law of structure prevailing through- 
 out this range of mountains, which, however simple 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 bend- 
 ing and fracture of the beds is greatest on the southeastern 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 posi- 
 tion. By reference to the section (fig. 505), it will be seen that on the 
 
390 APPALACHIAN CHAIN. [On. XXV 
 
 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 (I) 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 diagram 
 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 indicated by the dotted 
 lines at i and k. 
 
 The movements which imparted so uniform an order of arrangement 
 to this vast system of rocks must have been, if not contemporaneous, 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 ex- 
 erted on the southeastern 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 southeast was the quarter 
 whence the coarser materials of these strata were derived, so that the an 7 
 cient land lay in that direction. The conglomerate which forms the gen- 
 eral base of the coal-measures is 1500 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 northwest, and dwindles gradually 
 away when followed still farther in the same direction, until its thickness 
 is reduced to 30 feet.* The limestones, 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 thin- 
 ning out as they go westward, 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, cr- where the hydrographical basin of the Missis- 
 sippi is now situated. 
 
 In that region, near Pottsville, where the thickness of the coal-meas- 
 ures is greatest, there are thirteen seams of anthracitic coal, several of 
 them more than 2 yards tljick. Some of the lowest of these alternate 
 
 * H. D. Rogers, Trans. Assoc. Amer. Geol. 1840-42, p. 440. 
 
CH. XXV.] 
 
 UNION OF COAL-SEAMS. 
 
 391 
 
 with beds of white grit and conglomerate of coarser grain than I ever 
 saw elsewhere, associated with pure coal. The pebbles of quartz ar< 
 often of the size of a hen's egg. On following these pudding-stones and 
 grits for several miles from Pottsville, by Tamaqua, to the Lehigh Sum- 
 mit Mine, in company with Mr. H. D. Rogers, in 1841, he pointed out 
 to me that the coarse-grained strata and their accompanying scales 
 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 anthracite coal quarried in the open air at Mauch 
 Chunk (or the Bear Mountain), the overlying sandstone, 40 feet Jiick, 
 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, 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 un- 
 mixed with earthy ingredients, can, I think, be accounted for in no other 
 way, than by the growth, during thousands of years, of trees and ferns, 
 in the manner of peat, a theory which the 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 sediment, or, in this case, of sand and pebbles, wholly un- 
 explained. 
 
 "But the student will naturally ask, what can have caused so many 
 seams of coal, after they had been persistent for miles, to come together 
 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 act,', fig. 506, be a mass of vegetable matter, capable, 
 
 Fig. 506. 
 
 when condensed, of forming a 3-foot seam of coal. It rests on the 
 underclay b 6', filled with roots of trees in situ, and it supports a grow- 
 ing 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 de- 
 
HOKIZONTAL COAL STEATA. [Cn. XXV. 
 
 faying, their stumps and tlie lower parts of their trunks being enveloped 
 in layers of sand and mud, which are gradually filling up the lake DF 
 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 accumulate from c to F. We then find in the region F, two 
 seams of coal (a f and g') each 3 feet thick, and stparated by 25 feet of 
 sandstone 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 the re- 
 gion 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 gener- 
 ation 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. 390), 
 that the strata of the Appalachian coal-field assume a horizontal posi- 
 tion 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 (6), 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 a), and may be fol- 
 lowed the whole way to Pittsburg, fifty miles distant. As it is nearly 
 horizontal, while the river descends it crops out at a continually increas- 
 ing, but never at an inconvenient, height above the Monongahela. Be- 
 low the great bed of coal at Brownsville is a fire-clay 1 8 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 greatei 
 height. Here almost every proprietor can open a coal-pit on his own 
 land, and the stratification being very regular, he may calculate with 
 jrecision the depth at which coal may be won. 
 
 The Appalachian coal-field, of which these strata form a part (from c 
 
CH. XXV.] 
 
 APPALACHIAN COAL STEATA. 
 
 
 S'S 
 
 i ! 
 
 IF 
 
 * 
 
 2 S S 
 ^2* 
 o! 
 
 111 
 
 ^ll 
 tf<j 
 
 to E, section, fig. 505, p. 390), is remarkable for its vast area ; for, ac- 
 cording to Professor H. D. Rogers, it stretches continuously 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 denu- 
 
394: CONVEKSION OF COAL INTO LIGNITE. [0* XXV 
 
 dation, 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. 390), 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 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 southeastward towards the more bent and distorted rocks. 
 Thus, on the Ohio, the proportion of hydrogen, oxygen, and other vola- 
 tile matters, ranges from forty to fifty per cent. Eastward of this line, 
 on the Monongahela, it still approaches forty per cent., where the strata 
 begin to experience some gentle flexures. On entering the Alleghany 
 Mountains, where the distinct anticlinal axes begin to show themselves, 
 but before the dislocations are considerable, the volatile matter is gene- 
 rally in the proportion of eighteen or twenty per cent. At length, when 
 we arrive at some insulated coal-fields (5', fig. 505) associated 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 an- 
 thracite.* 
 
 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 decom- 
 pose slowly and evolve carbonic acid gas, thus parting with a portion of 
 their original oxygen. By this means, they become gradually converted 
 into lignite or wood-coal, which contains a larger proportion of hydrogen 
 than wood does. A continuance of decomposition changes this lignite 
 into common or bituminous coal, chiefly by the discharge of 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 giren. 
 
 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 gas- 
 eous 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 pene- 
 trating these cracks, when the great movements took place, which have 
 rent and folded the Appalachian strata. It is well known that, at the 
 
 * Trans, of Assoc. of Amer. Geol. p. 470. 
 
CH. XXV.] CLIMATE OF COAL PEKIOD. 395 
 
 present period, thermal waters and hot vapors burst out from the earth 
 during earthquakes, and these would not fail to promote the disengage- 
 ment of volatile matter from the carboniferous rocks. 
 
 Continuity of seams of coal. As single seams of coal are continuous 
 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 l^ growing ; and these may in after 
 ages appear to geologists to have been continuous, although in fact they 
 were simply contemporaneous. Denudation may easily be imagined in 
 such cases as the cause of interruptions, which were, in fact, original. 
 But as in all the American coal-fields there are numerous root-beds with- 
 out 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 pro- 
 longed without 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, espe- 
 pecially 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 bonanist taught that a tropi- 
 cal climate was implied by the carboniferous flora, geologists might well 
 be at a loss to reconcile the preservation of so much vegetable matter with 
 a high temperature ; for heat hastens the decomposition 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 resembling that now enjoyed in the equa- 
 torial zone. Tree-ferns range as far south as the southern part of New 
 Zealand, and Araucarian pines occur in Norfolk Island. A great pre- 
 dominance of ferns and lycopodiums indicates moisture, equability of 
 temperature, and freedom from frost, rather than intense heat ; and we 
 know too little of the sigillariae, 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 Moun- 
 tain Limestone, they belong to families of whose climatal habits we know 
 
396 CAEBONIFEKOUS KEPTILES. [ CH - XXV. 
 
 nothing ; and even if they should be thought to imply that a warm tem- 
 perature characterized the northern seas in the carboniferous era, the 
 absence of cold may have given rise (as at present in the seas of the Ber- 
 mudas, under the influence of the Gulf-stream) to a very wide geographical 
 rang of stone-building corals and shell-bearing cuttle-fish, without its 
 being necessary to call in the aid of tropical heat. 
 
 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 contemporaneous air-breathing 
 creatures should have been discovered. No vertebrated animals more 
 highly organized than fish, no mammalia or birds, no saurians, frogs, tor- 
 toises, or snakes were known in rocks of such high antiquity. In the 
 coalfields 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 ichthyolites 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, especially those of the family called Sauroid by Agassiz ; as 
 Megalichthys, 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 Fj 509 
 
 teeth striated longitudinally (see fig. 509), the ar- 
 ticulations of the spinous processes with the verte- 
 bra, and other characters. Yet they do not form 
 a family intermediate between fish and reptiles, but 
 are true fish, though doubtless more highly organ- 
 ized than any living fish.* 
 
 The annexed figure represents a large tooth of 
 the Holoptychius, found by Mr. Homer, in the 
 Cannel coal of Fifeshire. This fish probably in- 
 habited an estuary, like many of its contemporaries, 
 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- 
 Appel in Ehenish Bavaria, by H. von Meyer, under 
 the name of Apateon pedestris, the animal being Fifeshire coal-field. { 
 supposed to be nearly related to the salamanders. 
 
 Three years later, in 1847, Prof, von Dechen found in the coal-field of 
 Saarbruck, at the village of Lebach, between Strasburg and Treves, 
 
 * Agassiz, Poiss. Foss. vol. ii. p. 88, <fec. 
 
CH. XXV.] 
 
 CARBONIFEROUS REPTILES. 
 
 397 
 
 Fig. 510. 
 
 the skeletons of no less than three distinct species of air-breathing 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 re- 
 mains 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 of 
 these reptiles have been faith- 
 fully preserved in the centre 
 of spheroidal concretions of 
 clay-iron-stone. The largest 
 of these lizards, Archegosau- 
 rus 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 Goldfuss as 
 saurians, but by Herman von 
 Meyer as most nearly allied 
 to the Ldbyrinthodon, and 
 therefore, as before explained 
 (p. 340), having many char- 
 acters intermediate between 
 batrachians and saurians. The 
 remains of the extremities 
 leave no doubt that they were quadrupeds, " provided," says von Meyer, 
 " with hands and feet terminating in distinct toes ; but these limbs were 
 weak, serving only for swimming or creeping." The same anatomist has 
 pointed out certain points of analogy be- Fi 
 
 tween their bones and those of Proteus 
 anguinus ; and Prof. Owen has observed 
 to me that they make an approach to the 
 Proteus in the shortness of their ribs. Two 
 specimens of these ancient reptiles retain a 
 large part of the outer skin, which con- 
 sisted of long, narrow wedge-shaped, tile-like, and horny scales, arranged 
 in rows. (See fig. 51L) 
 
 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 Khine, Dr. King pub- 
 lished an account of the footprints of a large reptile discovered by him 
 
 * Ooldfuss, Neue Jenaische Lit. Zeit. 1848 ; aud Von Meyer, Quart. GeoL 
 Journ. voL iv. Miscell. p. 61. 
 
 Archegosauiw minor, Goldfnss. Fossil reptile from 
 the coal-measures, Saarbriick. 
 
 Imbricated covering of skin of Archf* 
 
 gosaurus medius, Gold! ; 
 
 magnified* 
 
398 
 
 FOOTPKENTS OF 
 
 Fig. 512. 
 
 [Cn. XXV. 
 
 Scale one-sixth th# original. 
 
 Slab of sandstone from the coal-measures of Pennsylvania, with footprints of 
 air-breathing reptile and casts of cracks. 
 
 in North America. These occur in the coal strata of Greensburg, in 
 Westmoreland county, Pennsylvania ; and I had an opportunity of ex- 
 amining them in 1846. I was at once convinced of their genuineness, 
 and declared my conviction on that 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 accompanying drawing 
 (fig. 512). It displays, together with footprints, the casts of cracks (a, 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 5, 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 impres- 
 
Ca XXV.J 
 
 AIR-BREATHING REPTILES. 
 Fig. 513. 
 
 399 
 
 Series of reptilian footprints in the coal-strata of "Westmoreland 
 county, Pennsylvania. 
 
 a. Mark of nail? 
 
 sions ; 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 the 
 same quarry before it was abandoned, the greater part of them so ar- 
 ranged (see fig. 513) on the surface of one stratum as to imply 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 nearly equal 
 
400 FOOTPKINTS OF EEPTILIANS. [Cn. XXV 
 
 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. 337), both the hind 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 Cheiro- 
 therium, 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 
 Cheirotherium was evidently a broader animal, and belonged to a dis- 
 tinct 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 mentioned (p. 
 392), three yards thick, 100 feet above it, and worked in the neighbor- 
 hood, with several other seams of coal at lower levels. The impressions 
 of Lepidodendron, Sigillaria, Stigmaria, and other characteristic car- 
 boniferous plants are found both above and below the level of the reptil- 
 ian footsteps. 
 
 Analogous footprints of a large reptile of still older date were after- 
 wards found (1849) at Pottsville, 70 miles N. E. of Philadelphia, by Mr. 
 Isaac Lea, in a formation of red shales, called Ko. XL by Prof. H. D. 
 Rogers, in the State Survey of Pennsylvania, and referred by him to the 
 base of the coal, but regarded by some geologists as the uppermost part 
 of the Old Red Sandstone. A thickness of 1700 feet of strata intervenes 
 between the footprints of Greensburg, before described, and these older 
 Pottsville impressions. In the same Red Shale, No. XL, the " debatable 
 ground" between the Carboniferous and Devonian group, Prof. H. D. 
 Rogers announced in 1851 that he had discovered other footprints, re- 
 ferred 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 foot- 
 print 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 footsteps 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 Sau- 
 rian, rather than to a Batrachian or Chelonian. With these footmarks 
 *vere seen shrinkage cracks, such as are caused by the sun's heat in mud. 
 
 * See Lyell's Second Visit, &c., vol. ii. p. 305. 
 
CH. XXV.] AIR-BREATHERS IN THE COAL. 401 
 
 and rain-spots, with the signs of the trickling of water on a wet, sandy 
 beach ; all 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 of a reptile were obtained from the 
 coal-measures of America by Mr. Dawson and myself. We detected 
 them in the interior of one of the erect Sigillariae before alluded to as of 
 such frequent occurrence in Nova Scotia. The tree was about two feet 
 in diameter, and consisted, as usual, of an external cylinder of bark, con- 
 verted into coal, and an internal stony axis of black sandstone, or rather 
 mud and sand stained black by carbonaceous matter, and cemented to- 
 gether 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 vertebrae of a rep- 
 tile, 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 batra- 
 chians, now inhabiting the North American rivers. The same view was 
 afterwards confirmed by Prof. Owen, who also pointed out the resem- 
 blance 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 whatever other manner it entered, must 
 be matter of conjecture. 
 
 Footprints of two reptiles of different sizes had previously been ob- 
 served by Dr. Harding and Dr. Gesner on ripple-marked flags of the 
 lower coal-measures in Nova Scotia, evidently made by quadrupeds walk- 
 ing on the ancient beach, or out of the water, just as the recent Meno- 
 poma is sometimes observed to do. 
 
 In 1853 Prof. Owen announced the first discovery of fossil reptilian 
 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 footprints, 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 anirtals of a 
 higher grade than fishes in the Coal, or in any rocks older than the Per- 
 mian. Even now, it may be said, that we have scarcely made any pro- 
 
 * Geol. Quart. Journ. vol. ix. p. 58. 
 26 
 
402 AIR-BREATHERS IN THE COAL [On. XXV 
 
 gress in obtaining a knowledge of the terrestrial fauna of the coal, since 
 the reptiles above enumerated seem to have been all amphibious. Nega- 
 tive 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 five millions of tons of native coal are annually 
 extracted from the coal-measures, yet no fossil insect has yet been met 
 with in the carboniferous 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, 
 Bulimus, 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 Mammals, 
 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 invertebrata, or the entire ab- 
 sence 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 car- 
 boniferous reptiles which have been established within the last ten years 
 on the evidence of bones and footprints. Yet our opportunities of ex- 
 amining 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 re- 
 specting 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 unpre- 
 pared state to serve as a dwelling-place for organized beings, cannot ex- 
 plain the enigma, because we know that while the land supported a lux- 
 uriant 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 problem, 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. 
 
 403 
 
 CARBONIFEROUS OR MOUNTAIN LIMESTONE. 
 
 It has been already stated (p. 359), 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 struc- 
 ture 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 triassic to the most modern, inclusive. The 
 accompanying diagrams (figs. 514, 515) may illustrate these types ; and, 
 although it may not always be easy for any but a practised naturalist to 
 
 Fig. 514. 
 
 Paleozoic type of lamelliferous cup-shaped Coral. Order ZOANTHARIA ECGOSA, Milne Edwards 
 and Jules Haime. 
 
 a. Vertical section of Campophyllum flexuosum (Cyatho- 
 phyllum, Goldfuss); nat size: from the Devonian of 
 the Eifel. The lamella* are seen around the inside of the 
 cup; the walls consist of cellular tissue : and large trans- 
 verse plates, called tabulce, divide the interior into cham- 
 bers. 
 
 6. Arrangement of the lamella in Polyccdia prof undo,, Ger- 
 mar, sp. ; nat size: from the Magnesian Limestone, Dur- 
 ham. This diagram shows the quadripartite arrangement 
 of the lamellae characteristic of paleozoic corals, there being 
 four principal and eight intermediate lamella?, the whole 
 number in this type being always a multiple of four. 
 
 c. Stauria astrceceformis, Milne Edwards. Young group, 
 nat size. Upper Silurian, Gothland. The lamellae in 
 each cup are divided by four prominent ridges into four 
 groups. 
 
 Fig. 515. 
 
 Neozoic type of lamelliferons cup-shaped Coral. Order ZOAXTHAEIA APOBOSA, M. Edwards and 
 
 J. Haitne. 
 
 a. Para&nttia centrali*, Man tell, sp. Vertical section, nat size. 
 Upper Chalk, Gravesend. In this type the lamellae, are mas- 
 sive, and extend to the axis of loose cellular tissue, without 
 any transverse plates like those in fig. 514 a. 
 
 J. Cyathina Bowerbankii, Edwards and Haime. Transverse 
 section, enlarged. Gault Folkstone. In this coral the lameUm 
 are a multiple of six. The twelve principal plates reach the 
 central axis or columella, and between each pair there are 
 
 three secondary plates, in all forty-eight The short interme- 
 diate plates which proceed from the columella are not counted. 
 They are ca,\\ed pali. 
 
 c. Fungia patettaris, Lamk. Eecent : very young state. Dia- 
 gram of its six principal and six intermediate septa, magnified. 
 The sextuple arrangement is always more manifest in the 
 young than in the adult state. 
 
 recognize the points of structure here described, every geologist should 
 understand them, as the reality of the distinction is of no small theoreti- 
 cal interest. 
 
404: 
 
 FOSSILS OF THE 
 
 [Cn. XXT. 
 
 ft will be seen that the more ancient corals have what is called a 
 quadripartite arrangement of the stony plates or lamellae, 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 ancient 
 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 temperature of. the waters of the primeval 
 seas, inasmuch as the two groups of zoophytes are constructed on essen- 
 tially different types. When the great number of the paleozoic and neo- 
 zoic species is taken into account, it is truly wonderful to find how con- 
 stant the rule above explained holds good ; only one exception having as 
 yet occurred of a quadripartite coral in a neozoic formation (the creta- 
 ceous), and one only of the sextuple class (a Fungia ?} in paleozoic 
 (Silurian) rocks. 
 
 From a great number of lamelliferous corals met with in the Mountain 
 Limestone, two species have been selected, as having a very wide range, 
 extending from the eastern borders of Russia to the British Isles, and 
 being found almost everywhere in each country. 
 
 Fig. 516. 
 
 Fig. 517. 
 
 Lithostrotion Ixitaltiforme, Phil. sp. (Li- 
 thostrotion striatum, Fleming ; Astrcea 
 basaltiformis, Couyb. and Phill.) Ken- 
 dal; Ireland; Russia; Iowa, and west- 
 ward of the Mississippi, "United States. 
 (D. D. Owen.) 
 
 Lonsclateia Jtoriformis (Martin, sp.) 
 M. Edwards. (Lithostrotionfloriforme, 
 Fleming. Strombodes.*) 
 
 a. Young specimen, with buds on the 
 disk. 
 
 "b. Part of a full-grown compound mass. 
 Bristol, &c. ; Eussia. 
 
 These fossils, together with numerous species of Zaphrentis, Amplexus. 
 Cyathophyllum, Clisiophyllum, Syringopora, and Michdinea* form a 
 group widely different from any that preceded or followed them. 
 
 * For figures of these corals, see Paleontographical Society's Monographs, 1852, 
 
Cn. XXV.] 
 
 MOUNTAIN LIMESTONE. 
 
 405 
 
 Of the Bryozoa, the prevailing forms are Fenestella and Polypora, and 
 these often form considerable beds. Their net-like fronds are easily rec- 
 ognized. 
 
 Crinoidea are also numerous in the Mountain Limestone. (See figs. 
 518,519.) 
 
 Fig. 518. 
 
 Fig. 519. 
 
 Cyatfiocrinitts planuz, 
 Miller. Body and 
 arms. Mountain 
 Limestone. 
 
 Cyathocrinu* caryocrinoidei, M'Coy. 
 a. Surface of one of the joints of the stem. 
 6. 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 .6, is greatly 
 developed in size in proportion to the arms, although this is not the case 
 in fig. 518. The genera Poteriocrinus, Cyathocrinus, Pentremites, 
 Actinocrinus, and Platycrinus, are all of them characteristic 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 Pro 
 ductus, such as P. giganteus, P. hemisphcericus, P. semireticulatus (fig. 
 521), and P. scabriculus. Large plaited spirifers, as Spirifer siriatus, 
 
 Fig. 521. 
 
 Fig 520. 
 
 fAUxoAinus gigas, M'Coy. Eeduced. 
 Mountain Limestone : 
 Ireland. 
 
 Producing semireticulatus, Martin, sp. 
 (P. antiquatu*. Sow.) Mountain 
 Limestone. England ; Enssia ; the 
 Andes, &c. 
 
406 
 
 FOSSILS OF THE 
 
 [On. XXV 
 
 . rotundatus, and S. trigonalis (fig. 522), also abound ; and smooth 
 species, such as Spirifer glaber (fig. 523), with its numerous varieties- 
 
 Fig. 523. 
 
 Spirifer 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 pat- 
 tern of the original colored stripes which ornamented the living shell. 
 (See fig. 524.) These colored bands are also preserved in several lamel- 
 libranchiate 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 Pleuroto- 
 maria (fig. 526), which displays wavy blotches, resembling the coloring 
 in many recent Trochidse. 
 
 Fig. 524. 
 
 Fig. 525. 
 
 Terebratula hastata, 
 Sow., with radiating 
 bands of color. 
 Mountain Lime- 
 stone. Derbyshire : 
 Ireland ; Kussia, &c. 
 
 Aviculopecten sublobatus, 
 Phill. Mountain Lime- 
 stone. Derbyshire ; 
 Yorkshire. 
 
 Pleurotomaria carinata, Sow, 
 
 (P.jlammigera, Phill.) 
 Mountain Limestone. Derby- 
 shire, &c. 
 
 The mere fact that shells of such high antiquity should have preserved 
 the patterns of their coloring, is striking and unexpected ; but Prof. E. 
 Forbes has deduced from it an important geological conclusion. He 
 infers that the depth of the primeval seas in which the Mountain Lime- 
 stone was formed, did not exceed 50 fathoms. To this opinion he is led 
 by observing, that in the existing seas the testacea which have colors 
 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 exam- 
 ples in the British seas of testacea which are always white or colorless 
 when taken from below 100 fathoms ; and yet individuals of the same 
 species, if taken from shallower zones, are vividly striped or banded. 
 
CH. XXV.] 
 
 MOUNTAIN LIMESTONE. 
 
 407 
 
 This information, derived from the color of the shells, is the more 
 welcome, because the Kadiata, Articulata, and Mollusca of the Carbo- 
 niferous* 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 Avicula, Nucula, 
 Soiemya, and Lithodomus, belong no doubt to existing genera ; but the 
 majority, though often referred to living types, such as Isocardia, Turri- 
 tella, and Buccinum, belong really to forms which appear to have become 
 extinct at the close of the paleozoic epoch. Euomphalus is a character- 
 istic univalve shell of this period. In the interior it is often divided into 
 chambers (fig. 527 d), the septa or partitions not being perforated as in 
 
 Fig. 527. 
 
 Euomphalus pentagulattit, Sowerby. Mountain Limestone. 
 a, Upper side ; &, lower, or umbilical side ; c, view showing mouth, which 
 is less pentagonal in older individuals ; d, view of polished section, showing 
 internal chambers. 
 
 foraminiferous 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 
 communication with it by a septum. The number 
 of chambers is irregular, and they are generally 
 wanting in the innermost whorl. The animal of 
 the recent 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 
 living Argonaut, occur in the Mountain Lime- eiierophon<x>8tatus,Sow. 
 stone. The genus is not met with in strata of 
 
 Mountain Limestone. 
 
4u8 FOSSILS OF MOUNTAIN LIMESTONE. [On. XXV. 
 
 later date. It is most generally regarded as belonging to the 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 representatives 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 uncoiled and straightened (fig. 529). 
 Some species of this genus are several feet long. The Goniatite is another 
 
 Fig. 529. 
 
 Portion of Orthoceras laterale, Phillips. Mountain Limestone. 
 
 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 sc 
 approach nearer to the form of those of the Nautilus. The dorsal position 
 
 Fig. 530. Fig. 531. 
 
 Goniatites crenistria, Phill. Mountain Goniatites cvolutus, Phillips. 
 
 Limestone. N. America ; Britain ; Mountain Limestone. 
 
 Germany, &c. Yorkshire. 
 
 a. Lateral view. 
 
 &. Front view, showing the mouth. 
 
 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 Moun- 
 tain Limestone of Belgium, he had found no more than four or five ex- 
 amples 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 investigation of other coun- 
 tries has led to quite a different result. Thus, near Clifton, on the Avon, 
 
OH. XXV.] 
 
 LOWER CARBONIFEROUS STRATA. 
 
 409 
 
 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. 
 249), massive palatal teeth fitted for grinding. (See figs. 532, 533.) 
 
 Fig. 582. 
 
 Fig. 533. 
 
 Psammodu* porosus, Agas. Bone-bed, Mountain 
 Limestone. Bristol; Armagh. 
 
 Cochliodits contortus, Agas. Bone-bed, 
 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 numerous. The great 
 Meyalichthys 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 Nummulites and 
 their numerous minute allies, appears in the Mountain Limestone to be 
 restricted to a very few species, the individuals, however, of which are 
 vastly numerous. Textularia, Nodosaria, Endothyra, 
 and Fusulina (fig. 534), have been recognized. The 
 first two genera are common to this and all the after 
 periods ; the third has already appeared in the Upper 
 Silurian, but is not known above the Carboniferous ; Magnified 3 diam. 
 the fourth (fig. 534) is peculiar to the Mountain Lime- MoQntain Limestone. 
 stone, and is characteristic of the formation in the United States, Russia. 
 and Asia Minor. 
 
 Fie. 534 
 
 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 char- 
 acter, 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 formerly referred to the 
 Devonian group, but are now ascertained to belong to the " Lower Car- 
 
410 CAKBONIFEROUS LIMESTONE OF N. AMEEICA. [Cu. XXV 
 
 boniferous." The prevailing shell which characterizes the carbonaceous 
 schists of this series, both on the Continent and in England, is Posido- 
 nomya Becheri (fig. 535). Some well- 
 known mountain-limestone species, such 
 as Goniatites crenistria (see fig. 530) 
 and 6r. 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 common; also Knorria, 
 Calamites Suclcovii, and C. transi- 
 tionis, Gopp., some peculiar, others spe- 
 cifically identical with ordinary coal-measure fossils. The true geological 
 position of these rocks in the Hartz was first determined by MM. Murchi- 
 son and Sedgvvick in 1840.* 
 
 CARBONIFEROUS LIMESTONE IN NORTH AMERICA. 
 
 The coal-measures of Nova Scotia have been described (p. 377). The 
 lower division contains, besides large stratified masses of gypsum, some 
 bands of marine limestone almost entirely made up of encrinites, and, in 
 some places, containing shells of genera common to the mountain lime- 
 stone of Europe. 
 
 In the United States the carboniferous limestone underlies the pro- 
 ductive coal-measures ; and, although very inconspicuous on the margin 
 of the Alleghany or Great Appalachian coal-field in Pennsylvania, it ex- 
 pands in Virginia and Tennessee. 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 regionsf it is about 400 feet thick, and abounds, as in 
 Europe, in shells of the genera Productus and Spirifer, with Pentremitcs 
 and other crinoids and corals. Among the latter, Lithostrotion basalti- 
 forme or striatum (fig. 516, p. 404), or a closely-allied species, is common. 
 
 * Trans. Geol. Soc. London, 2d series, vol. yi. p. 228. 
 f Owen's Geol. Survey of Wisconsin, <fec, 1852. 
 
CH. XXVL] OLD BED SANDSTONE. 
 
 CHAPTER XXVL 
 
 OLD RED SANDSTONE, OR DEVONIAN GROUP. 
 
 Old Red Sandstone of the Borders of "Wales Of Scotland and the Sonth of 
 Ireland Foseil reptile and foot-tracks at Elgin Fossil Devonian plants at 
 Kilkenny Ichthyolites of Clashbinnie Fossil fish, crustaceans, <fec., of Caith- 
 ness and Forfarshire Distinct lithological type of Old Red in Devon and 
 Cornwall Term Devonian Organic remains of intermediate character be- 
 tween 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. 332), that the carbonifer- 
 ous strata are surmounted by a system called " The New Red," and un- 
 derlaid 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 calcareous matter is wanting, and where its color 
 is determined by the red oxide of iron. 
 
 " Old Red " in Herefordshire, &c. In Herefordshire, Worcestershire, 
 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. 
 
 2d. 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 Cepha- 
 laspis 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. Strickland.* 
 
 Old Red Sandstone of Scotland and Ireland. South of the Gram- 
 pians, in Forfarshire, Kincardineshire, and Fife, the Old Red Sandstone 
 may be divided into three groups. 
 
 * Murchison's Siluria, p. 245. 
 
412 FOSSIL EEPTILE OF OLD RED SANDSTONE. [Ca XXVI. 
 
 Fig. 536. 
 
 A. Yellow sandstone, with some bands of white sandstone. 
 
 B. Red shale, sandstone with cornstone, and at the base a conglomer- 
 
 ate (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 Sandstone 
 of Fife above alluded to. They contain large rhombcidal scales of a 
 fish called by Agassiz Stayonolepis Robertsoni, and referred by him to 
 the Dipterian family. This family, ob- 
 serves Mr. Hugh Miller, is emphati- 
 cally characteristic of the Old Red 
 Sandstone. The scales of this Sta- 
 gonolepis, the only parts of the species 
 yet known, are so like those of Glyp- 
 topomus in form and pattern that they 
 may possibly 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-colored 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 Elginetise. (Mantell.) 
 Natural size. 
 
 Eeptile in the Old Eed Sandstone, from 
 near Elgin, Morayshire. 
 
Ca. XXVL] FOSSIL FOOTPRINTS OF " OLD RED.' 
 
 413 
 
 The matrix is a fine-grained whitish sandstone, with a cement of carbon- 
 ate 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 Salamanders. 
 
 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 Brickenden 
 observed, in 1850, on a slab of sandstone from the same quarry at Cum- 
 mingstone, 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 parallel rows ; the hind foot being 
 
 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 Brickenden. 
 
 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 re- 
 semble 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. 400) to trails referred by American geolo- 
 gists 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 Professor H. D. Rogers con- 
 ceives, or as the uppermost Devonian, as some have contended (see p. 400). 
 They at least demonstrate that certain quadrupeds, of larger size than 
 any of the bones that have been found in carboniferous rocks, existed at 
 
4:14: 
 
 FOSSILS OF THE 
 
 [CH. XXVI. 
 
 the time when the ancient Red Shale, usually termed, in the United 
 States, " infra-carboniferous," 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, charac- 
 teristic 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 Cyclopteris (see figs. 538 
 and 539). The sterns of the latter have, in some specimens, broad bases 
 of attachment, and may therefore have been tree-ferns. 
 
 Fig. 588. 
 
 Fig. 539. 
 
 Stem of Lepidodendron, so compressed as 
 to destroy the quincunx arrangement of 
 the scars. Upper Devonian, Kilkenny. 
 
 Cyclopteris Ifibernica, Forbes. 
 Upper Devonian, Kilkenny. 
 
 In the same strata shells having the form of the genus Anodon, and 
 which probably belonged to freshwater testacea, occur. Some geologists, 
 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. 359) ; but the associated ichthy elites 
 and the distinct specific character of the plants, seem to favor the opinion 
 above expressed. 
 
 B. (Table, p. 412.) 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, 
 Fi 54Q 2dly, of a conglomerate, seen both at 
 
 the foot of the Grampians, a-nd 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 en- 
 tire specimen, more than 2 feet in 
 length, was afterwards found by Mr. 
 
 Scab of Holopiyehius nobihwmus, Agas. ' 
 
 Clashbinnie. Nat. size. Noble. Some of these scales (see ng. 
 
 540) measured 3 inches in length, and 2 in breadth. 
 
 ^mamy\i 
 
CH. XXVI.] 
 
 OLD EED SANDSTONE . 
 
 415 
 
 C. (Table, p. 412). The third or lowest division south of the Gram- 
 pians consists of gray paving-stone and roofing-slate, with associated red 
 and gray shales ; these strata underlie a dense mass of conglomerate. In 
 these gray beds several remarkable fish have been found of the genus 
 named by Agassiz Cephalaspis, or " buckler-headed," from the extraor- 
 dinary shield which covers the head (see fig. 541), and which has often 
 been mistaken for that of a trilobite, such as Asaphus. 
 
 Fig. 541. 
 
 Cephala&pis Lyettii, Agass. Length 6| inches. 
 From a specimen in my collection found at Glammiss, in Forfarshire ; see other figures, 
 
 Agassiz, vol. ii. tab. 1 a, 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 quarrymen the 
 " Seraphim," from the wing-like form and feather-like ornament of the 
 hinder part of the head, the part most usually met with. Agassiz, having 
 
 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. 
 
 8. The proximal portion of one of the great anterior clnws. 
 
 4. Termination of the same, with the serrated pincers. (See Agass. Poiss. Foss. du Yienx 
 Gres Eouge, plate A.) 
 
 1 and 2 are of the natural size ; 3 and 4 are reduced one half. 
 
416 
 
 FOSSILS OF THE 
 
 [Cn. XXVI. 
 
 Fig. 548. 
 
 previously referred some of these fragments to the class of fishes, was the 
 first to recognize their true nature, and 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 con- 
 sists of ten or eleven movable rings 
 (the exact number is not ascer- 
 tained), and was terminated by an 
 oval-pointed tail. The whole sur- 
 face is covered by the scale-like 
 markings before mentioned as or- 
 namenting the head. Prof. M'Coy, 
 to whom I owe these notes on the 
 general structure, has kindly fur- 
 nished 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 gray 
 beds of Forfarshire, containing the 
 Pterygotus, may not be referable to the Upper Silurian or Upper Ludlow 
 beds ; but, as they are associated at Balrudderie with numerous speci- 
 mens of Cephalaspis (the bony bucklers or head-pieces alone being pre- 
 served), apparently belonging to two species, I think it far more probable 
 that they constitute a division of the " Old Red," and perhaps not so an- 
 cient a one as the bituminous schists (6, p. 418) in the North of Scotland. 
 
 In the same gray paving-stones and coarse roofing-slates in which the 
 Cephalaspis and Pterygotus occur, in Forfarshire and Kincardineshire, the 
 remains of grass-like plants abound in such numbers as to be useful to the 
 geologist by enabling him to identify corresponding 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 deter- 
 mined. 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 gray 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 
 * Siluria, p. 247. 
 
 Pterygotus problematicus, Agassiz. 
 Kestoration by Professor M'Coy. 
 
CH. XXVL] 
 
 OLD EED SANDSTONE. 
 
 417 
 
 same beds in the Sidlaw Hills, at all the points where fig. 4 is introduced 
 in the section, p. 48. 
 
 Fig. 544. 
 
 Fig. 545. 
 
 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 Eed, Fife. 
 
 Fig. 546. 
 
 Dr. Fleming has compared these fossils to the panicles of a Jurtcus, or 
 the catkins of Sparganiurn, or some allied plant, and he was confirmed in 
 this opinion by finding a specimen at Balrudderie, showing the undei 
 surface smoother than the upper, and displaying what 
 may be the place of attachment of a stalk. I have met 
 with some specimens in Forfarshire imbedded in sand- 
 stone, and not associated with the leaves of plants (see 
 fig. 544), which bore a considerable resesemblance 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 pressing 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 organisms. 
 
 The late Dr. Mantell was so much struck with the resemblance of one 
 
 Fig. 547. 
 
 Fig. 543. 
 
 Fossil Old Eed. 
 
 Fig. 549. 
 
 Eecent 
 
 Fig. 547. Slab of Old Eed Sandstone, - 
 Forfarshire, with bodies like the _ 
 ova of Batrachians. J. f 
 
 a. Ova ? in a carbonized state. I & 
 6. Egg-cells ?, the ova shed. J 
 Fig. 548. Eggs of the common frog, 
 liana temporaria, in a carbon- 
 ized state, from a dried-up pond in 
 Clapham Common. 
 
 a. The ova. 
 
 b. A transverse section of the p 
 
 mass exhibiting the form of 
 the egg-cells. 
 
 Fig. 549. Shale of Old Eed Sandstone, or 
 Devonian, Forfarshire, with impression 
 of plants and eggs of Batrachians ? 
 a. Two pair of ova? resembling 
 those of large Salamanders 01 
 Tritons on the same leaf 
 6, 5. Detached ova? 
 c. Egg-cells (?) of frogs or Ranina. 
 
418 OLD EED OF NOETH OF SCOTLAND. [Cm XXVI 
 
 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 car- 
 bonaceous state (see fig. 548) from the mud of a pond near London, that 
 he suggested a batrachian origin for the fossil ; and Mr. Newport con- 
 curred 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 Devonian 
 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 consisting of a nucleus of 
 granite, gneiss, and other hypogene rocks, which seem as if set in a sand- 
 stone 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 sand- 
 stone 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-colored sandstones, and containing the Telerpeton of 
 Elgin, has been already classed, A., p. 412, as the equivalent of the yel- 
 low sandstone of Fife. That upper member passes downwards into red 
 and variegated sandstone and conglomerate, which may correspond with 
 the beds called B., in the same section at p. 412. To the above succeeds, 
 in the descending order, " the middle formation" of Mr. Hugh Miller, com- 
 posed of thin, fissile, gray sandstone, in which, in Morayshire, Dr. Malcolm- 
 son found a species of Ccphalaspis ; but whether these beds are of the 
 age of the paving-stone of Arbroath (C. Table, p. 412) is as yet uncertain. 
 
 Next below is the " inferior division" of Hugh Miller, comprising 
 
 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 counties 01 
 Banff, Nairn, Moray, Cromarty, and Caithness, and also in Orkney, be- 
 longing to the genera Pterichthys (fig. 550), Coccosteus, Diplopterus, 
 Dipterus, Cheiracanthus, Asterolepis, and others described by Agassiz. 
 * " Old Red Sandstone," 1841. 
 
'OH. XXVL] 
 
 TERM " DEVONIAN." 
 
 419 
 
 Pterichthys, Agassiz ; upper side, showing 
 mouth ; as restored by H. Miller.* 
 
 Five species of Ptericlitliys have been found in this lowest divi- 
 sion of the Old Red. The wing- 
 like appendages, whence the 
 genus is named, were first sup- 
 posed by Mr. Miller to be pad- 
 dles, 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 con- 
 siders the tail to have been the 
 only organ of motion. The ge- 
 nera Dipterus and 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. Asmusii, 
 Eichwald, the species characteristic of the Old Red Sandstone of Russia 
 as well as that of Scotland, attained the leDgth of between 20 and 30 
 feet. It was clothed with strong bony armor, embossed with star-like 
 tubercles, but it had only a cartilaginous skeleton. The mouth was 
 furnished with two rows of teeth, the outer ones small and fish-like, the 
 inner larger and with a reptilian character.f The Asterolepis oocurs also 
 in the Devonian rocks of North America, in the lower division of the 
 Old Red. Coniferous wood, with structure showing medullary rays, has 
 likewise been detected in the lower division by Hugh Miller,| who has 
 pointedly dwelt on the importance of the fact, as the oldest example yet 
 known of so higily organized 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, pre- 
 viously referred to the " transition" or Silurian series, were found to be- 
 long in reality to the period of the Old Red Sandstone. For this reform 
 we are indebted to the labors 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 Carboniferous 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 paleonto- 
 logical observations alone would not have enabled us to assign, with accu- 
 
 * Old Red 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. 
 
420 DEVONIAN" SERIES. FCn, 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 183 7, 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, con- 
 necting as it does the paleontology of the Silurian and Carboniferous 
 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 sand- 
 stone. But the whole series is much altered and disturbed by the intru- 
 sion 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.* 
 
 Upper - 
 
 Middle^ 
 
 Lower 
 
 'T 
 u 
 
 Devonian Series in North Devon, 
 a. Calcareous brown slates ; with fossils, many of them common to 
 
 1. { the Carboniferous grotip. (Barnstaple, Pilton, <fcc.) 
 
 Brown and yellow sandstone, with shells and land-plants Stig- 
 maria, Knorria, and others. (Baggy Point, Marwood, &c.) 
 
 2. Hard gray and reddish sandstones and micaceous flags, without 
 
 fossils, resting on soft greenish schists of considerable thickness. 
 (Morte Bay, Bull Point, <fcc.) 
 
 3. Calcareous slates, with eight or nine courses of limestone, full of 
 
 corals and shells like those of the Plymouth limestone. (Combe 
 Martin, Ilfracombe Harbor, &c.) 
 
 4. Hard, greenish, red, and purple sandstones ; with occasional fossils, 
 
 Spirifers, <fec. (Linton, North Foreland, tfcc.) 
 
 5. Soft chloritous slates, with some sandstones ; Orthis, Spirifer, and 
 some Corals. (Valley of Rocks, Lynmouth, <fcc.) 
 
 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.f Other geologists, at home and 
 abroad, have successively identified them with the Devonian series in 
 France, Belgium, the Rhenish Provincesj Central Germany, and Amer- 
 
 * Sedgwick and Murchison, Trans. Geol. Soc., New Series, vol. v. p. 644. De 
 la Bechc, Geol. Report, Devon and Cornwall, pi. 3. Murchison's Siluria, p. 256. 
 f Quart. Journ. Geol. Soc. vol. viii. p. 1, et seg. 
 
CH. XXVI.] 
 
 UPPER AND MIDDLE DEVONIAN. 
 
 421 
 
 Fig.551. 
 
 ica.* 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, 6 of the preceding 
 section) are represented in Cornwall by the limestones and slates of Pether- 
 wyn, which rise in like manner from under the Culm Measures, consti- 
 tuting the Petherwyn group of Prof. 
 Sedgwick. These beds contain the 
 very common Spirifer disjunctus, 
 Sow. (S. Verneuilii, Murch.), (see 
 fig. 551), a species distributed over 
 the whole of Europe, and found even 
 in Asia Minor and China. Among 
 many other fossils the Clymenia 
 linearis (fig. 552) and the minute 
 crustacean Cypridina serrato-striata (fig. 553) are so characteristic of 
 these upper beds in Belgium, the Rhenish Provinces, the Hartz, Saxony, 
 
 Fig. 552. 
 
 Fig.55a 
 
 Spirifer di&junctus. Bow. 8711. Sp. Ver- 
 
 neuilii. March. 
 Upper Devonian, Boulogne. 
 
 Cypridina serrato-striata. Sandberger. 
 Weilburg, &c. ; Nassau; Saxony; Bel- 
 gium. 
 
 Clymenia linearis, Miinster. 
 Petherrpn, Cornwall ; Elbersreuth, Bavaria. 
 
 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 carbonifer- 
 ous limestone. 
 
 Middle Devonian 
 
 The unfossiliferous series (No. 2, p. 420) of North Devon, and the calca- 
 reous beds of Ilfracombe (3), correspond to the Dartmouth and Plymouth 
 
 * See Dr. Fridolin Sandberger on the Devonian rocks of Nassau (GeoL Verhalt. 
 Nassau) ; Fried. A. Roemer, on the Hartz Devonian Rocks, in Dunker and Von 
 Meyer's Palaeontographica, 3d voL pt 1. 
 
 f See Murchison's Siluria, chapters x. xiv. and xv. 
 
422 
 
 FOSSILS OF THE 
 
 [Ca XXVI 
 
 groups of Prof. Sedgwick's South Devon series, and are the most typical 
 portion of the Devonian system. They include the great limestones 01 
 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 Devonshire and a large part of Cornwall. 
 Among the corals we find the genera Favosites, Heliolites, and Cyatho- 
 phyllum, the last genus equally abundant in the Silurian and Carbonifer- 
 ous 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. 
 
 favoeites polymorpha, Goldf. 8. Devon, from a polished 
 specimen. 
 
 a. Portion of the same magnified, to show the pores. 
 
 a. CyatliophyUum ccvspitosum, 
 
 Goldf., Plymouth. 
 &. A terminal star. 
 c. Vertical section, exhibiting 
 
 transverse plates, and part of 
 
 another hranch. 
 
 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 figured, but afterwards grows 
 
 Fig. 55T. 
 
 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.) 
 
 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. 
 
CH. XXVI] 
 
 MIDDLE DEVONIAN. 
 
 423 
 
 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) may be mentioned as 
 
 Fig. 558. 
 
 Stringocephalus Burtini, Defr. (Terebratula porrecta, Sow.) Elfel; also South Devon. 
 a. Valves united. Z>. 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 
 
 exclusively Devonian. Many other Brachiopod shells, of the genus Spir- 
 ifer, &c., abounded, and among them the Atrypa reticularis, Linn. sp. 
 (fig. 575, p. 434), which seems to have been a cosmopolite species oc- 
 curring in Devonian strata from America to Asia Minor, and which, as 
 we shall hereafter see (p. 433), lived also in the Silurian seas. Among 
 the peculiar lamellibranchiate bivalves common to the Plymouth lime- 
 stone of Devonshire and the Continent, we find the Megalodon (fig. 559), 
 together with many spiral univalves, such as Murchisonia, .Euomphalus, 
 and Macrocheilus ; and Pteropods such as Conularia (fig. 560). The 
 
 Fig. 560. 
 
 Fig. 559. 
 
 Megalodon cticuttatus, Sow. Eifel ; also Bradley, S. Devon. Conularia ornata, D'Arch. et 
 a. The valves united. Dc Vern - 
 
 &. Interior of valve, showing the large cardinal tooth. (Geol. Trans. 2d s. vol. vi. pi. 29.) 
 
 Eefrath, near Cologne. 
 
 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. 421). Although 
 but few species of Trilobites occur, the characteristic Brontes flabellifer 
 (fig. 561 p. 424) is far more 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 Lime- 
 
24 
 
 LOWER DEVONIAN. 
 
 [On. XXVI 
 
 Fig. 561. 
 
 Fig. 562 
 
 Restored outline of head of Brontes 
 Jlabellifet' 
 
 Brontes flalellifer> Goldf. Eifel ; also S. Devon. 
 
 stone," or " Eifel Limestone" of Germany, several remains c Coccosteus 
 and other ichthyolites have been detected, and they serve, as Sir R. Mur- 
 chison observes (Siluria, p. 
 371), to identify the rock 
 with the Old Red Sandstone 
 of Britain and Russia. 
 
 Beneath the great Eifel 
 Limestone (the principal 
 
 Fig. 563. 
 
 Caleeola sandalina, Lam. Eifel ; also South Devon, 
 a. Ventral valve. &. Inner side of dorsal valve. 
 
 type of " the Devonian" on 
 
 the Continent), lie certain 
 
 schists called by German 
 
 writers " Calceola-schiefer," because they contain in abundance a fossil 
 
 brachiopod of very curious structure, Caleeola sandalina (fig. 563). 
 
 Lower Devonian. 
 
 Beneath the Middle Devonian limestones and schists already enumera- 
 ted, 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 ot 
 these rocks on the Rhine and in some of the adjacent countries were re- 
 garded as ' Upper Silurian" by Prof. Sedgwick and Sir R. Murchison in 
 1839, but tneir 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 (No. 4 and 5 of the section, p. 420), and, ac- 
 cording 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 distinguish the Fig ' 564 - 
 
 " Spirifer-sandstein" of 
 Germany have their rep- 
 resentatives in the De- 
 vonian strata of North 
 
 America (see fig. 564). Spirifer mucronatus, Hall. Devonian of Pennsylvania 
 
 * Murchison's Siluria, p. 368. 
 
CH. XXVL] 
 
 DEVONIAN OF EUSSIA. 
 
 425 
 
 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 De- 
 vonian." 
 
 With the above are associated many species of Brachiopods, such as 
 Orthis, Leptama, and Chonetes, and some Lamellibranchiata, such as 
 Pterinea ; also the very remarkable fossil coral, called Pleurodictyum 
 problematicum (fig. 566). 
 
 Fig. 565. 
 
 Fig. 566. 
 
 Pleurodictyum problematicum, Goldfass. Lower 
 Devonian ; Dietz, Nassau, &c. 
 
 Ola. Attached to a worm-like body (Serpula). 
 The specimen is a cast in sandstone, the thin ex- 
 panded base of the coral being removed, and ex- 
 posing the large polygonal cells ; the walls of these 
 cells are perforated, and the casts of these perfora- 
 tions produce the chain-like rows of dots between 
 the cells. 
 
 ffomalonotus armatus, Burmoister. Lower 
 
 Devonian ; Daun, in the Eifcl. 
 01)8. 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 Brit- 
 ish, whereas when they consist of limestone they contain shells similar to 
 those of Devonshire, thus confirming, as Sir Roderick observes, the con- 
 temporaneous 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 man- 
 ner 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. 414); Dendrodus strigatus, Owen ; 
 Pterichthys major, Ag. ; and many others. But some of the most 
 marked of the Scottish genera, such as Cephalaspis, Coccosteus, Diplacan- 
 thus, 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 the extinct species. On the 
 * Siluria, p. 329. 
 
4:26 DEVONIAN STRATA [On. XX VL 
 
 whole, no less than forty species of placoid and ganoid fish have been 
 already collected in Russia, some of the placoids being of enormous size, 
 as before stated, p. 419. 
 
 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 condition, so that the relative position of each formation can 
 be ascertained 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. Genesee f 
 
 5. Tully - - '- " - - 15 
 
 6. Hamilton ... 1000 
 
 7. Marcellus 50 
 
 8. Corniferous ) ^ 
 
 9. Onondaga J 
 
 10. Schoharie ) 
 
 11. Cauda-Galli grit \ 
 
 12. Oriskany sandstone ' - - - "-""" -' - 6 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 feet 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 Yerneuil 
 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 America in 1842, arrived independently at the 
 
 
CH. XXVL] IN THE UNITED STATES. 4:27 
 
 same conclusion.* The resemblance of the Spirifers of this Oriskany 
 sandstone to those of the Lower Devonian of the Eifel was the chief mo- 
 tive 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 Mur- 
 chison 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 paleo- 
 zoic strata, it has been well studied by Professors W. B. and H. D. Rogers. 
 The upper divisions (from the Catskill to the Genesee 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 thickness of 
 more than 50 feet, are observed to constitute an almost continuous 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 Tennessee 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 for- 
 mation at the falls or rapids of the Ohio River at Louisville in Kentucky, 
 where it much resembles 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 dis- 
 played, and, by the side of it, the Favistella, combining a similar honey- 
 combed 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," Catenipora escharoides (see fig. 579, p. 435), 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 sea- 
 son when the channel is laid dry. The waters of the Ohio, when I visited 
 the spot in April, 1846, were more than 40 feet below their highest level, 
 and 20 feet above their lowest, so that large spaces of bare rock were ex- 
 posed to view.f 
 
 * De Verneuil, Bulletin, 4, 678, 1847. D. Sharpe, Quart. Journ. Geol. Soc. vol 
 iv. pp. 145, 1847. 
 
 f Ly ell's Second Visit to the Ucited States, vol li. p. 277. 
 
428 DEVONIAN STKATA. [On. XXVI. 
 
 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 lati- 
 tudinal range of the Anthozoa, has an important bearing on the deter- 
 mination of the geography of the northern hemisphere during the Devo- 
 nian epoch. We must also remember that the corals of these ancient 
 reefs, whether. American or European, however recent maybe their aspect, 
 all belong to the Zoantharia rugosa, a suborder which, as before stated 
 (p. 403, 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."* 
 
 This calcareous division also contains Goniatites, Spirifers, Pentre- 
 mites, and many other genera of Mollusca and Crinoidea, corresponding 
 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 enumerated, with the members 
 of the European Devonian, is very great, so few are the species in com- 
 mon. 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. f Indeed we are scarcely as yet able to de- 
 cide 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. 
 
 * Geol. Quart. Journ. vol. x. pi. Ix. 1854. 
 
 f Report of Foster and Whitney on Geol. of Lake Superior, p. 802, Washing- 
 ton, 1851. 
 
CH. XXVIL] SILURIAN STRATA. 429 
 
 CHAPTER XXVIL 
 
 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 tmconforma- 
 bility Pentameri and Tentaculites Lower Silurian rocks Llandeilo flags 
 Cystideae Trilobites Graptolites Vast thickness of Lower Silurian strata in 
 Wales Foreign Silurian equivalents in Europe Ungulite grit of Eussia 
 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 Lin- 
 gula flags of North Wales Lower Cambrian Oldest known fossil remains 
 " Primordial group" of Bohemia Characteristic trilobites Metamorphosis of 
 trilobites Alum schists of Sweden and Norway Potsdam sandstone of United 
 States and Canada Footprints near Montreal Trilobites on the Upper Mis- 
 sissippi 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 Pa- 
 leontologists Doctrine of the non-existence of vertebrata in the older fossilif- 
 erous 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, viii., pp. 91 and 93. Geologists were also in the habit of ap- 
 plying to these older strata the general name of " grauwacke," 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 together by argillaceous matter. Far too much im- 
 portance 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 Murchison 
 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. 
 
430 
 
 SUBDIVISIONS OF SILURIAN ROCKS. [Ca XXVIL 
 
 UPPER SILURIAN ROCKS. 
 
 
 Prevailing Lithological ck- 
 
 
 /Viaro/tora iioeo in v^rgdiiio rtuiuiiio. 
 
 Feet. 
 
 
 r 
 
 r a. Tilestones. "| "] 
 
 
 
 Finely lamina- 1 
 
 Marine mollusca of 
 
 
 
 ted reddish and I 800 ? 
 
 almost every or- 
 
 
 T 
 
 green micaceous 
 
 der, the Brachio- 
 
 
 Upper 
 Ludlow. 
 
 sandstones. 
 
 poda most abun- 
 
 
 
 
 dant. Serpulites, 
 
 
 
 b. Micaceous gray " 
 
 
 Crustaceans of 
 
 1. Ludlow 
 
 
 sandstone and 
 
 
 the Trilobite fa- 
 
 formation. " 
 
 
 mudstone. 
 
 
 mily. Placoid 
 
 
 
 
 
 fish (oldest re- 
 
 
 Aymestry 
 limestone. 
 
 Argillaceous lime- 
 stone. 
 
 - 2000 
 
 mains of fish yet 
 known). Sea- 
 
 
 
 
 
 weeds ; and in 
 
 
 Lower 
 Ludlow. 
 
 ! Shale, with concre- 
 tions of lime- 
 
 
 the uppermost 
 strata land plants. 
 
 
 
 stone. 
 
 
 ! Wenlock 
 limestone. 
 1 
 
 1 Concretionary and " 
 thick-bedded 
 limestone. 
 
 1 Marine Mollusca of 
 various orders as 
 ^.UVYC , before. Crinoidea 
 
 . 
 
 Wenlock ' 
 shale. " 
 
 Argillaceous shale, 
 frequently flag- 
 stone. 
 
 * 2000 [ and corals plenti- 
 ful. Trilobites, 
 Graptolites. 
 
 MIDDLE SILURIAN ROCKS. 
 
 Caradoc j 
 formation. ( 
 
 Llandeilo j 
 formation. ( 
 
 Caradoc 
 sandstones. 
 
 Shale, shelly lime- "| 
 
 Cr idea ' 
 
 , - 11 
 
 stone, sandstone, I onnn Mollusca, chiefly 
 
 and conglome'- >00 j gj-Jj^ 
 
 [ merus abundant.) 
 
 LOWER SILURIAN ROCKS. 
 
 Llandeilo I 
 
 C Dark colored cal- ~) 
 careous flags ; ^ 
 
 slates and sand- 
 stones. 
 
 20,000 J 
 
 f Mollusca, Trilo- 
 bites, Cystideae, 
 Crinoids, Corals, 
 
 [_ Graptolites. 
 
 'UPPER SILURIAN ROCKS. 
 
 Ludlow formation. This member of the Upper Silurian group, as 
 will be seen by the above table, is of great thickness, and subdivided 
 into three parts, the Uppe : and the Lower Ludlow, and the intervening 
 Aymestry limestone. Each of these may be distinguished near the town 
 of Ludlow, and at other places in Shropshire and Herefordshire by pe- 
 culiar 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 
 Siluiian region. They were regarded as a transition 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 strata. Among these are Ortho- 
 
CH. XXVIL] UPPER SILURIAN BONE-BED. 431 
 
 ceras bullatum, Trochus ? helicites, Bellerophon trilobatus, Ckonetes lata, 
 <fec., with numerous defences of fishes. These beds are well seen at King- 
 ton in Herefordshire, and at Downton Castle near Ludlow, where they 
 are quarried for building. 
 
 b. Gray Sandstone, &c. The next subdivision of the Upper Ludlow 
 consists of gray calcareous sandstone, or very commonly a micaceous 
 stone, decomposing into soft mud, and contains, besides the shells 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 periods, the brachiopodous mollusca predominate over the 
 
 Fig. 567. Fig. 568. 
 
 Orthts elegantula, Dalm. Var. orbicularis, Athyris (Terebratulcf) navicttla, J. Sow. 
 J. Sow. Delbury. Aymestry limestone ; also in 
 
 Upper Ludlow. Upper and Lower Ludlow. 
 
 lamellibranchiate ; but the latter are by no means unrepresented. Among 
 other genera, for example, we observe Avicula (or Pterinea), Cardiola, 
 Nucula, Sanguinolites, and Modiola. 
 
 Some of the Upper Ludlow sandstones are ripple-marked, thus afford- 
 ing evidence of gradual deposition ; and the same may be said of the ac- 
 companying fine argillaceous shales which are of great thickness, 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 to the weather, are resolved into mud, 
 proves that, notwithstanding 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. Murchison, 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 Ludlow fossils.* At that 
 point immediately above the upper fish-bed numerous globular bodies 
 were found, which were determined by Dr. Hooker to be the spores of a 
 cryptogamic land-plant, probably Lycopodiaceous. These beds occur just 
 
 * Murchison's Siluria, pp. 137-237. 
 
4:32 FOSSILS OF UPPER LUDLOW. [On. XXVII. 
 
 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 
 
 Fig. 569. Fig. 570. 
 
 . Onchus tenuistriatus, Agass. Shagreen scales of a placoid fish 
 
 Bone-bed. Upper Silurian ; Ludlow. (Thelodus). 
 
 Bone-bed. Upper Ludlow. 
 
 may possibly belong to the same placoid fish. The jaw and teeth of 
 another predaceous genus (fig. 571) have also Fig. 571. 
 
 been detected. As usual in bone-beds, the 
 teeth and bones are, for the most part, frag- 
 mentary and rolled. Many statements have piectrodusmiraUUs, Agass. 
 been published of fish remains obtained from Bone-bed. Upper Ludlow. 
 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 Rock ;f and lower than this no one seems as yet to have suc- 
 ceeded 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 Sandstone, a formation which is still 
 considered as debatable ground between the Devonian and Silurian sys- 
 tems (see p. 426, above). 
 
 In England it is true, as in the United States and Canada, globular, 
 cylindrical, or flattened masses have been detected, composed 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 
 fcecal lumps, by creatures feeding on Lingulse a,nd Orbiculse, we cannot 
 decide that such feeders were of the vertebrate class, rather than. Cepha- 
 lopods, 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. 453, et seq. 
 
 * Geol. Quart. Journ. vol. vii. p. 263. 
 
 f Memoirs Geol. Surv. vol. ii. 
 
 \. Logan and Hunt ; Silliman's Journ. No. 50, 2d series, March, 1854. 
 
OH. XXVII. j 
 
 AYMESTEY LIMESTONE. 
 
 433 
 
 2. Aymestry limestone. The next group is a subcrystalline and 
 argillaceous limestone, which is in some places 50 feet thick, and dis- 
 tinguished around Aymestry by the abundance of Pentamerus Knightly 
 Sow. (fig. 572), also found in the Lower Ludlow. This genus of brachi- 
 
 Fig. 572. 
 
 Pentamerus Knightii, Sow. Aymestry. Half nat size. 
 a. View of both valves united. 
 &. Longitudinal section through both valves, showing the central plates :' septa. 
 
 opoda was first found in Silurian strata, and is exclusively a paleozoic 
 form. The name was derived from rtsvrs, pente, five, and ju.o, 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 chamber, 
 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, 
 Tcrebratula, and many other shells of this order. Messrs. Murchison 
 and De Verneuil discovered 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 Sweden. 
 
 Three other abundant shells in the Aymestry lime- 
 stone are, 1st, Lingula Lewisii (fig. 573) ; 2d, 
 Rhynchonella Wilsoni, Sow. (fig. 574), which is also 
 common to the Lower Ludlow and Wenlock lime- 
 stone ; 3d, Atrypa reticularis, Lin. (fig. 575), which 
 has a very wide range, being found in every part ol 
 the Silurian system, even in the upper portion of the 
 
 Fig. 5 
 
 Lingula Lewisii, 
 
 J. Sow. 
 Abberley Hills, 
 
 Llandeilo flags. 
 
 Fig. 574. 
 
 Rhynchonella (Terebratuld) Wilsoni, Sovr. Aymeetry. 
 28 
 
434 
 
 FOSSILS OF LOWER LUDLOW. [Cn. XXVII 
 
 Fig. 575. 
 
 Fig. 5T6. 
 
 Atrypa reticularis, Linn. (Terebratula affinis, Min. Con.) Aymestry. 
 a. Upper valve. &. 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 limestone and the Upper Lud- 
 low, and several of these are not found in the 
 Wenlock* 
 
 3. Lower Ludlow shale. This mass is a 
 dark gray 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 con- 
 voluted, nearly as in Spirula, 
 Phragmoceras ventricosum, j. Sow. The Orthoceras Ludense (fig. 578), as 
 
 (Orthoceras ventricosum, Stin.) ,, ,, , , 11, , j 
 
 Aymestry ; nat. size. well as the cephalopod last mentioned, is 
 
 peculiar to this member of the series. 
 
 Fig. 577. Fig. 578. 
 
 Lituites giganteus, J. Sow. 
 Near Ludlow ; also in the Aymestry 
 and Wenlock limestones; \ nat size. 
 
 Fragment of Orthoceras Ludense, J. Sow. 
 Lcintwardine, Shropshire. 
 
 A species of Graptolite, G. Ludensis, Murch. (fig. 588, p. 437), a form 
 of zoophyte which has not yet been met with in strata above the Silurian, 
 Dccurs plentifully in the Lower Ludlow. 
 
 * Murchison's Siluria, p. 133. 
 
Cn. XXVIL] 
 
 WEXLOCK FORMATION. 
 
 435 
 
 Fig. 5T9. 
 
 Wenlock formation. We next come to the Wenlock formation, which 
 has been divided (see Table, p. 430) into the Wenlock limestone 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 Shropshire, 
 ranging for about 20 miles from S. W. to N.E., about a mile distant from 
 the nearly parallel escarpment of the Aymestry limestone. This ridgy 
 prominence is due to the solidity of the rock, and to the softness of the 
 shales above and below it. Near Wenlock it consists of thick masses of 
 gray subcrystalline limestone, replete with corals and encrinites. It is 
 essentially of a concretionary nature, and the concretions, termed " ball- 
 stones" in Shropshire, are often enormous, even 
 80 feet in diameter. They are of pure carbo- 
 nate of lime, the surrounding rock being more 
 or less argillaceous.* Sometimes in the Mal- 
 vern Hills this limestone, according to Professor 
 Phillips, is oolitic. 
 
 Among the corals in which this formation is 
 so rich, the " chain-coral," Halysites catenula- 
 tus, or Catenipora escharoides (fig. 579), may 
 be pointed out as one very easily recognized, 
 and widely spread in Europe, ranging through 
 all parts of the Silurian group, from the 
 Aymestry limestone to near the bottom of the 
 series. Another coral, the Favorites Goth- 
 landica (fte. 580), is also met with in profusion Syo. Cateni 
 
 v '' . . Gold. Upper and Lower Silurian. 
 
 in large hemispherical masses, which break up 
 
 into prismatic fragments, 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 men- 
 
 Fig. 5SO. 
 
 Fig. 581. 
 
 Fdtositfs Gothlandica. Lam. Dudley. 
 
 a. 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. 
 
 (Cyathophyllum, Gold) 
 Wenlock Limestone, Shropshire. 
 
 * Murcbison's Siluria, p. 115. 
 
436 
 
 FOSSILS OF THE WENLOCK LIMESTONE. [Cn. XXVII 
 
 tioned (p. 403), exhibiting the quadripartite arrangement of the lamellae 
 within the cup. 
 
 Among the numerous Crinoids, several peculiar species of Cyathocrinus 
 (for genus, see figs. p. 405) contribute their calcareous stems, arms, and 
 cups towards the composition of the Wenlock limestone. 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 fig- 
 ure (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. 434), 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) depretsa, Sow. 
 Wenlock and Ludlow Eocks. 
 
 Pseudocrinites Mfasciatus, 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 
 
 Fig. 595. 
 
 Fig. 584 
 
 Calymene Blwnenbaehii, 
 
 Brong. 
 
 Wenlock, Ludlow, and 
 Aymestry limestones. 
 
 Fig. 586. 
 
 Sphcerexochus minis, Bey- 
 rich. Coiled up. 
 Dudley; also in Ohio, 
 N, America. 
 
 Phacops caudatu*, Brong. 
 Wenlock, Aymestry, and Ludlow Eocks. 
 
 * E. Forbes, Mem. Geol. Survey, vol. ii. p. 496. 
 
CH. XXVIL] 
 
 MIDDLE SILURIAN ROCKS. 
 
 437 
 
 mirus (fig. 586) 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 j- ig> 587. 
 
 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 per- 
 sistent member of the Wenlock formation, for the 
 limestone often thins out and disappears. The shale, 
 like the Lower Ludlow, often contains elliptical con- 
 cretions of impure earthy limestone. In the Malvern 
 district it is a mass of finely levigated argillaceous 
 matter, attaining, according to Prof. Phillips, a thick- 
 ness of 640 feet, but it is sometimes more than 1000 
 feet thick in Wales. The prevailing fossils, besides 
 corals and trilobites, and some crinoids, are several 
 small species of Or this, with other brachiopods and 
 certain thin-shelled species of Orthoceratites. One 
 species of G-raptolite, 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." araptoiithm Ludenti*, Murchison. 
 Of these fossils, which are more charac- Ludlow and Wenlock Shales. 
 
 teristic of the Lower Silurian, I shall again speak in the sequel (p. 442). 
 
 -va^ssSSS$!^ 
 
 MIDDLE SILURIAN 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 c^ 
 typical Caradoc is divisible into two formations, the lower, an arenaceous 
 form of 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 some 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 ot 
 our Government Survey. The larger part, therefore, of what was once 
 termed " the Caradoc" has merged into the Llandeilo, and is the equiva- 
 lent 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 by Professor 
 
 * Siluria, p. 111. 
 
438 CARADOC SANDSTONE. [Cn. XXVII. 
 
 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 lit- 
 toral aspect, as Littorina and Turritella, were deposited round the mar- 
 gin 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 K. Murchi- 
 son had stated, into the Wenlock Shale. 
 
 Subsequently Professor Sedgwick and Mr. M'Coy, pursuing their inves- 
 tigations independently of the Survey in North Wales, became convincedf 
 that the Caradoc beds of May Hill and the Malverns, constituting the 
 Upper Caradoc, already mentioned, were full of Upper Silur an 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 E. Murchison, and where they found the Upper Caradoc 
 unconformable on the lower, and filled with a series of very distinct 
 fossils.^ 
 
 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 characterized by species 
 of Pentamerus and Atrypa unknown in the overlying Wenlock or Lud- 
 low beds, but which descend into the strata of the Llandeilo group. Pen- 
 tamerus Icevis (fig. 589), and P. ollongus may be particularly mentioned 
 
 Fig. 589. 
 
 Pentamerus Icevis, Sow. Caradoc Sandstone. 
 Perhaps the young of Pentamerus oblongus. 
 , I. 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 onco occupied by the septum being represented by a hol- 
 
 low in which is seen a cast of the chamber within the septum. 
 
 * Quart. Geol. Journ. vol. iv. p. 29 7. f Geol. Quart. Journ. 1852. 
 
 i Geol. Quart. Journ. vol. x. p. 62. 
 
CH. XXVIL] LOWER SILURIAN ROCKS. 439 
 
 as brachiopods which abounded in Siluria, and had a very wide geo- 
 graphical range, being met with in the same place in the Silurian series 
 of Russia and the United States. Among 
 its fossils, too, Tentaculites annulatus (fig. ^f^^^^Bf^ ' 
 590), an annelid probably allied to Ser- 
 pula, is exceedingly common. This also 
 is a link to connect it with the Lower 
 rather than the Upper Silurian. All the 
 shelly sandstone of the Malvern and Ab- 
 berly Hills, of Tortworth in Gloucester- 
 
 shire, and of the centre of the May Hill Eastnor Park ; nat. size and mag- 
 
 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 stale, 2000 
 feet in thickness, in the higher and disturbed regions of North Wales, as 
 in the Berwyn Mountains for example. According to Professor Sedg- 
 wick the hard quartzose Coniston Grits of Westmoreland may also he 
 referred to the same period. 
 
 LOWER SILURIAN ROCKS. 
 
 Llandeilo Flags. The Lower Silurian strata were originally divided 
 oy Sir R. Murchison into an upper group, already described, and termed 
 the Caradoc Sandstone, and a lower one, called, from a town in Caer- 
 marthenshire, the Llandeilo Flags. The strata last mentioned consist of 
 dark-colored micaceous flags, frequently calcareous, with a great thickness 
 of shales, generally black, below them. The same beds are also seen a 
 Builth in Radnorshire, and here they are interstratified with rolcanic 
 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. 438), are asso- 
 ciated 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), Helioliles, 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 Sphceronites 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, 6). They are considered by Professor E. Forbes 
 as intermediate between the crinoids and echinoderms. The Spha3ronite 
 here represented (fig. 591) occurs in the Llandeilo beds in Wales,f as 
 also in Sweden and Russia. 
 
 Examples are not wanting, though very rare, of star-fish in the same 
 
 * Murchison's Siluria, p. 178. 
 
 f Quart. Geol. Journ. vol. vii. p. 11 ; and Mem. Geol. Surv. vol. ii. p. 518. 
 
140 
 
 LOWER SILURIAN ROCKS. 
 
 [On. XXVII. 
 
 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 particularly characteristic. 
 Such shells as Atrypa and Spirifer, so fre- 
 quent in the Upper and Middle Silurian, are 
 rare or confined to the superior part of the 
 Lower Silurian, while Chonetes and Produc- 
 tus are wholly absent. It is remarkable, 
 however, that Rhynchonella and Lingula, 
 genera of which there are living representa- 
 tives in the present seas, were common in 
 the Silurian ocean. 
 
 EcMnospTicerites baltieus, Eich- 
 wald, sp. (Of the family Cys- 
 tidece.) 
 a. Mouth. 
 &. Point of attachment of stem. 
 
 Lower Silurian, S. and N. Wales. 
 
 Fig. 592. 
 
 "Tig. 598. 
 
 Fig. 594. 
 
 Ortliis tricenaria, 
 
 Hall. 
 
 New York. Canada. 
 nat. size. 
 
 Orthis vespertilio, Sow. 
 Shropshire ; N. and S. 
 
 Wales. 
 % nat. size. 
 
 Strophomena (Orthis) grandis, Sowerby. 
 
 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. 407), and some of the floating tribes of mollusca 
 (Pteropods). The Crustaceans were plentifully represented by the Trilo- 
 bites, 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 and 598) are especially characteristic 
 
 Fig. 595. 
 
 Fig. 596. 
 
 Asaphus tyrannus, Murch. 
 Llandeilo ; Bishop's Castle, &c. 
 
 Ogygia Buchii, Burm. (Asaphus 
 JBuchii, Brongn.) 
 
 Builth, Radnorshire ; Llandeilo, Caermarthenshire. 
 
CH. XXVIL] 
 
 LLANDEILO FLAGS. 
 
 of strata of this age, if not entirely confined to them ; but very numerous 
 other genera accompany these. Burmeister, in his work on the organi- 
 zation 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 arc 
 rarely met with. Some of his figures of the metamorphoses of the com- 
 mon Trinucleus are copied in the annexed wood-cuts (figs. ,597, 598). 
 
 Fig. 593. 
 
 Young individuals of Trinucleus con- 
 centricu* (T. ornatus, Barr.) 
 
 a. Youngest state. Natural size and 
 
 magnified ; the body rings not at all 
 developed. 
 
 b. 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 moult- 
 ed its crust 
 
 Trinucleus concentricus, Eaton. 
 Syn. T. caractaci, 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 col- 
 lected 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 theVirgularia and Pennatula, genera of which 
 the living species now inhabit mud and slimy sediment. The most emi- 
 nent naturalists still hold to this opinion. 
 
44:2 
 
 THICKNESS OF SILUKIAN STRATA. [CH. XXV1L 
 
 Fig. 599. 
 
 Fig. 600. 
 
 
 Didymograpsus geminus, Hisinger, sp. 
 Sweden. 
 
 a, Z>. Didymoffrapsus (Graptolited) Hur- 
 chisoiiii, Beck. 
 
 Llandeilo Flags. "Wales. 
 
 Fig. 601. 
 
 Fig. 602. 
 
 Diplogr 
 
 rapsus folium, 
 isinger. 
 
 Scotland; Sweden. 
 
 Fig. 603. 
 
 Diplo(jrapsus pristis, 
 Hisinger, sp. 
 
 Shropshire; Wales; Sweden, 
 &c. 
 
 Rastrites peregrinus, Barrande. 
 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 Si- 
 lurian, 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 sedimentary origin we might well expect, 
 from the analogy of other parts of the earth's crust, to find that they 
 must be referred paleontologically to more than one era ; in other words, 
 that changes in animal and vegetable life, as great as those which oc- 
 curred in the course of several such periods as the Devonian, Carbonifer- 
 ous, and Permian, would be found to have taken place while the accumu- 
 lation of so enormous a pile of rocks was effected. But in volcanic archi- 
 pelagoes, 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 outpour- 
 ing 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 op- 
 erations 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. 443 
 
 Nevertheless, there would seem to be a limit to the thickness of stony 
 masses formed even under such favorable circumstances, for the analogy 
 of tertiary volcanic regions lends no countenance to the notion that sed- - 
 imentary 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. Portlock's Report on Ty- 
 rone, 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 Sweden, 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 lime- 
 stone containing Pentamerus ollongus, 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 ex- 
 hibiting 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 Siphonotetra (see 
 figs. 604, 605). As bearing on the antiquity of this formation, it is in- 
 teresting to notice that both genera have recently been found in our own 
 Dudley limestone. 
 
 * Murchison's Siluria, p. 321. 
 
44A 
 
 SILURIAN STRATA OF UNITED STATES. [On. XXVIL 
 
 Shells erf the lowest known Fossiliferous Beds in Russia. 
 
 Fig. 605. 
 
 a 
 
 Obolus 
 
 Siphonotreta 
 
 From the lowest Silurian Sandstone, 
 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. 
 &. Exterior of the upper (dorsal) valve. 
 (Davidson.) 
 
 Among the green grains of the sandy strata above mentioned, Pro- 
 fessor 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 Gruttulina). 
 
 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. 388. But these 
 formations can be studied still more advantageously 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. 426.) 
 
 British Equivalents. 
 
 New York Names. 
 
 1. Upper Pentamerus Limestone 
 
 2. Encrinal Limestone 
 
 3. Delthyris Shaly Limestone 
 
 4. Pentamerus Limestone 
 
 5. Tentaculite Limestone 
 
 6. Onondaga Salt-group 
 
 7. Niagara Group 
 
 8. Clinton Group 
 
 9. Medina Sandstone 
 
 10. Oneida Conglomerate 
 
 11. Gray Sandstone 
 
 12. Hudson River Group 
 
 13. Utica Slate 
 
 14. Trenton Limestone 
 
 15. Black- River Limestone 
 
 16. Bird's-Eye Limestone 
 
 17. Chazy Limestone. 
 
 18. Calciferous Sandstone 
 
 19. Potsdam Sandstone 
 
 Upper Silurian (or Ludlow and 
 Wenlock formations). 
 
 I Middle Silurian (or Caradoc Sand- 
 j stone). 
 
 j- Lower Silurian (or Llandeilo beds). 
 
 j 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, such 
 
Cm XXVII.] SPECIFIC AGKEEMEXT OF FOSSILS. 445 
 
 as MM. de Verneuil, D. Sharp, Prof. Hall, and others, \vho have entered 
 upon this comparison, admit that there is a marked general correspond- 
 ence 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 fol- 
 lowing 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, JBlumenbachii, Homalonotus delphinocephalus (fig. 587), with 
 several other trilobites ; Rhynchonella Wilsoni, and It. cuneata ; Orthis 
 elegantula, Pentamerus galeatus, with many more brachiopods ; Qrtho- 
 ceras annulatum, among the cephalopodous shells ; and Favosites goth- 
 landica, with other large corals. 
 
 2d. 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. 437. 
 
 3d. That the Hudson River Group, No. 12, and the Trenton Lime- 
 stone, No. 14, agree paleontologically with the Llandeilo flags, containing 
 in common with them several species of trilobites, such as Asaphus (Iso- 
 telus) gigas, Trinucleus concentricus (fig. 598, p. 441) ; and various 
 shells, such as Orthis striatula, Orthis biforata (or 0. lynx), 0. porcata 
 ( 0. occidentals of Hall), Bellerophon bilobatus, &c.* 
 
 Mr. D. Sharpe, in his report on the inollusca 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 gasteropods and lamellibranchiate 
 bivalves of North America can be identified specifically with European 
 fossils, while no less than two-fifths of the brachiopoda, of which my col- 
 lection 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 
 geographical 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 Lime- 
 stone, have been considered by M. de Verneuil as Lower Silurian, because 
 they contain certain species, such as Asaphus (Isotelus) gigas, TUcenus 
 crassicauda, and Orthoceras bilineatum, in common with the overlying 
 Trenton Limestone.]; But, according to Professor Hall, the Illcenus was 
 
 * See Murchison's Siluria, p. 414. f Quart. Geol. Journ. voL iv. 
 
 \ Soc. Geol. France, Bulletin, vol. iv. p. 651, 1847. 
 
446 CANADIAN EQUIVALENTS. [Ca. XXVII, 
 
 erroneously identified, an error to which he confesses that he himself con- 
 tributed ; 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 gen- 
 eral 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 Canadian 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 
 
 Fossils from Allumette Kapids, River Ottawa, Canada, 
 a Fig. 606. 
 
 Maclurea Logani, Salter. 
 a. View of the shell. &. Its curious operculnm. 
 
 characteristic of the Chazy Limestone, or No. 17 ; Fi s- 607 - 
 
 and Murchisonia gracilis (fig. 607) is another 
 Trenton Limestone species found in the same Silu- 
 rian limestone of Canada ;j while one of the most 
 common shells in it is the Raphistoma ? (Euom- 
 phalus) uniangulatum, Hall, a species character- 
 istic in New York of the Calciferous Sandstone 
 
 itself. Murchisonia gracilis, Hall. 
 
 In Canada, as in the State of New York, the 4 ft 
 Potsdam Sandstone underlies the above-mentioned f ?* roS! 
 calcareous rocks, but contains a different 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 dif- 
 fusion throughout the " primaeval seas" of one' uniform specific fauna was 
 
 * Hall ; Forster and Whitney's Report on Lake Superior, Pt. II. 1851. 
 \ Logan, Report Brit. Assoc. Ipswich, pp. 59, 63. 
 
Cn. XXVIL] CAMBRIAN GROUP. 447 
 
 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 orthidifonn brachiopoda ; fifthly, the absence 
 or great rarity of fossil fish. 
 
 It is doubtless true that some living Terebratulae, on the coast of Aus- 
 tralia, 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 re- 
 marked 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 Mediterranean, 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 con- 
 sideration. 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 origi- 
 nally 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 Professor 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, therefore, to give a new name to the Llandeilo beds, 
 or to call them Cambrian, as has been recently proposed by some geol- 
 ogists, would be to act in violation of the ordinary rules of classifica- 
 
 * E. Forbes, Anniv. Address, 1854, Quart. Journ. GeoL Soc. voLx. p. 88. 
 f Siluria, p. 485. 
 
448 
 
 LINGULA FLAGS OF NORTH WALES. [On. XXVII. 
 
 tion, and would create much confusion, by disturbing a nomenclature 
 long received 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 quartzose rocks, sterile of fossils, or yielding 
 little more than some obscure fucoids. In North Wales, Professor Sedg- 
 wick 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 forma- 
 tions, to which he affixed names. Collectively they constituted the chief 
 part of the rocks called by him " Cambrian." They were devoid of lime- 
 stone ; but in a group of micaceous sandstones Mr. E. Davis discovered 
 in 1846 the Lingula named after him, and from which the name of 
 "Lingula flags" has since been denved. In these flags, about 1500 or 
 2000 feet in thickness, several other fossils were afterwards found, of dif- 
 ferent species from those in the Llandeilo beds. Amongst them, trilo- 
 bites, Agnostus and Conocephalus (for genus, see fig. 614), and some rare 
 Brachiopoda and Bryozoa, still unpublished by our Government survey- 
 ors, 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). 
 
 Fossils of the " Lingula Flags" or lowest Fossiliferous Hocks of Britain, 
 
 Fig. 609. Fig. 610. 
 
 Hymenocaris vermicauda, 
 
 Salter. 
 
 A Phyllopod Crustacean. 
 | nat. size. 
 
 "Lingula Flags" of Dolgelly, and Ffestiniog; N. Wales. 
 
 Lingula Davisii, M'Coy. 
 
 a. natural size. 
 
 &. Distorted by cleavage. 
 
 Olenus mierurus, 
 
 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 Oyygia 
 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. 442, that, when- 
 ever 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. 103), and our lines of separation may 
 
CH. XXVII. ] LOWER CAMBRIAN. 449 
 
 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 theTremadoc Slates, 1000 feet thick, and next theLingula 
 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 de- 
 scending order, comprising, first, 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 Pro- 
 fessor Forbes has given the name of Oldhamia (figs. 611 and 612). The 
 position of these rocks has been decided by the Government Surveyors, 
 
 The most Ancient Fossils yet known (1854). 
 Fig. (511. 
 
 Oldhamia radiata, Forbes. 
 Wicklow, Ireland. 
 
 Oldhamia antiqua, Forbes. 
 Wicklow, Ireland. 
 
 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 " Lingula 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 im- 
 perfect materials for classification. This will continue to be the case, 
 however many steps we may make in future in penetrating into the re- 
 moter annals of the past. 
 
 29 
 
450 
 
 PKIMOEDIAL GKOUP OF BOHEMIA. [Cn. XXVII 
 
 Bohemia. M. Barrande, in his admirable monograph on the Paleozoic 
 rocks of Bohemia, has laid much stress on the distinctness and isolation 
 of what he calls the "Protozoic schists," which attain a thickness of 120C 
 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 Cys- 
 tideee, 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, Oonocephalus (fig. 614), Ellipso 
 
 Fossils of the lowest Fossiliferous Beds in Bohemia^ or " Primordial Zone " of Barrande. 
 Fig. 613. Fie. 614. 
 
 Conocfphtdux fitriatux, Emmrieh. 
 
 nat. size. 
 Ginetz and Skrey. 
 
 Paradoxides Bohemicus, Barr. 
 
 About one-third natural size. 
 "Lowest Silurian Beds" of 
 
 Ginetz, Bohemia. 
 (Etage C. of Barrande.) 
 
 Fig. 617. 
 
 Fig. 615. 
 
 Aflnostus integer, Beyrich. 
 Nat. size and magnified. 
 
 Fig. 616. 
 
 Agnostus Rem, Barr. 
 
 Nat. size, Skrey. 
 
 cephalus, Sao (fig. 617), Arionellus, and 
 Hydrocephalus. They have all a facies of 
 their own, dependent on the multiplication 
 of their thoracic segments, and the dimi- 
 nution of their caudal shield or pygidium. 
 All the Bohemian species differ as yet 
 , ,, a from any found in England,' which may 
 
 Sao nirmtta, Barrande, in its various * * 
 
 stages of growth. Skrey. be owing chiefly to the very small num- 
 
 The small lines beneath indicate the , , , /-< , -r> 
 
 true size, in the youngest state, a, ber as yet known in brreat 13ntam ; or it 
 
 may be due entirely to the influence of 
 geographical causes. It seems, neverthe- 
 ] ess 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 formations of Barrande have each 
 of them many species in common with the successive subdivisions of the 
 British series. 
 
 5& ^ 
 
 but the facial sutures are not com- 
 
 pleted ; at e the full-grown animal, half 
 
 its true size, is shown. 
 
C.T. XXVII.] POTSDAM SAXDSTOXE OF X. AMERICA. 451 
 
 One of the so-called " primordial" Trilobites of the genus Sao, a form 
 not found as yet elsewhere in the world, has afforded M. Barrande 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 representation in the accompany- 
 ing figures, that the reader may learn the gradual manner in which differ- 
 ent segments of the body and the eyes make their appearance. When 
 we reflect on the altered and crystalline 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 Bohemian strata, may well excite our astonishment, and may rea- 
 sonably 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 
 antecedent 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, es- 
 pecially 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. An- 
 gelin, in his " Pateontologica 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 segments scarcely de- 
 veloped, and others again have the number of segments excessively mul- 
 tiplied, as in Paradoxides. These peculiarities agree with the characters 
 of the crustaceans met with in the Upper Cambrian strata, before men- 
 tioned. 
 
 United States and Canada. In the table, at p. 444, 1 have already 
 pointed out the relative position of the Potsdam Sandstone, which has 
 long been known as the lowest fossil iferous 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 TOO feet thick in Canada ; the lower portion consisting 
 of a conglomerate with quartz pebbles ; the upper part of sandstone con- 
 taining fucoids, and perforated by small vertical holes, which are very 
 characteristic of the rock, and appear to have been made by annelids 
 (Scolitkus linearis). 
 
 On the banks of the St. Lawrence, near Beauharnois and elsewhere, 
 
452 FOOTPRINTS NEAR MONTREAL. [Cn. XXVII 
 
 many fossil footprints have been observed on the surface of its rippled 
 layers. These impressions were first noticed by Mr. Abraham, of Mon- 
 treal, 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 Professor Owen to cor- 
 rect 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 im- 
 pressed 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 be- 
 tween the outermost impressions varies from 3j to 5^ inches, which 
 would imply a creature of much larger dimensions than any organic body 
 yet obtained from strata of such antiquity. 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 conglomerates. Together with the associated igne- 
 ous 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 un- 
 common. This phosphate, as Mr. Logan suggests, may have " a possible 
 connection 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 imagination can venture to follow." 
 
 Valley of the Upper Mississippi. Mr. Dale Owen has recently pub- 
 lished a graphic sketch, in his survey of Wisconsin (1852), of the lowest 
 
 * Quart. Geol. Journ. vol. viii. p. 210. 
 
CH. XXVIL] PERIOD OF INVERTEBRATE ANIMALS. 
 
 453 
 
 Fig. 618. 
 
 sedimentaiy rocks near the head-waters of the 
 Mississippi, lying at the base of the whole 
 Silurian series. They are many hundred feet 
 thick, and for the most part similar in char- 
 acter to the Potsdam Sandstone above de- 
 scribed, but including in their upper portions 
 intercalated bands of magnesian limestone, and 
 in their lower some argillaceous beds. Among 
 the shells of these strata are species of Lingula 
 ind Orthis, and several trilobites of the new 
 genus Dikelocephalus (fig. 618). These rocks, 
 occurring in Iowa, Wisconsin, and Minnesota, Dikdocephai 
 
 , . , , , T i Dale Owen, i diameter. 
 
 seem destined hereafter to throw great light A large crustacean of the oienoid 
 
 on the state of organic We in the Cambrian 
 
 period. Six beds containing trilobites, sepa- Mississippi. 
 
 rated by strata from 10 to 150 feet thick, are already enumerated. 
 
 Relation of Silurian and Cambrian Faunas. That there is a con- 
 siderable connection between the Cambrian and lower Silurian faunas, 
 notwithstanding that nearly every species may be 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, there- 
 fore, we had only trilobites in the latter, its generic relationship to the 
 Silurian fauna would appear greater than that of the Silurian to the Cam- 
 brian. 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 farther 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 abundant, and 
 amongst them some of a highly organized structure, referred to the genus 
 Onchus. We are indebted to Sir R. Murchison for having first an- 
 nounced, 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 that the active researches of the 
 last fourteen years in Europe and America " have failed to modify that 
 
454 UPPER SILURIAN BONE-BED. [Cn. XXVII. 
 
 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 re- 
 mains of fish are on record as coming from any stratum older than the 
 base of the " Upper Ludlow." (See above, p. 432.) When we reflect on 
 the number of Mollusks, Echinoderrns, 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 invertebrate, "emained 
 wholly untenanted by vertebrate animals. In the first place, we must 
 remember that we have detected no insects, or land-shells, or freshwater 
 pulmoniferous mollusks, or terrestrial crustaceans, or plants (except fu- 
 coids), 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 important for- 
 mations. 
 
 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 implying transportation from a distance. The associa- 
 tion of the spores of Lycopodiacese (see p. 432) 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 ich- 
 thyolites. 
 
 It has been suggested that Cephalopoda were so abundant in the Si- 
 lurian period that they may have discharged the functions of fish ; to 
 which we may reply that both classes coexisted in the Upper Silurian 
 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 theorize with confidence on the absence 
 of such relics over wide spaces at former eras. 
 
CH. XXVIL] ABSENCE OF FISH IX LOWER SILURIAN. 455 
 
 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 ? 
 forest on which thousands of mammalia and reptiles may have flourished 
 for centuries. In the summer of 1850, Professor 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 Shetland, 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 grov-nds off the Shetland 
 Islands for shells without obtaining the bones <r 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 vertebrae 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 sub- 
 stances are removed after death by chemical processes, or by the 
 digestive powers of predaceous beasts ; so that, if at some future period 
 a geologist should seek for monuments of the former existence ot 
 such creatures, he must look anywhere rather than in the area where 
 they flourished. He must search for them in spots which were cov- 
 ered at the time with water, and to which somes 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 tracing 
 back the signs of Vertebrata to formations of high antiquity. Such facts 
 
456 
 
 PROGEESSIVE DISCOVERY OF VERTEBRATA [Cn. XXVII 
 
 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 ; show- 
 ing the gradual Progress made in tracing them to Rocks of higher 
 Antiquity. 
 
 Year. 
 f 1798. 
 
 Mammalia, -I ,g,g 
 [ 184-7.' 
 ( 1782. 
 
 Aves. 
 
 ( 1839. 
 
 51710. 
 1844. 
 1852. 
 1709. 
 1793. 
 
 Pisces. 
 
 1828. 
 1840. 
 
 Formations. 
 Middle Eocene (or B. i. p. 222). 
 
 Lower Oolite. 
 Upper Trias. 
 
 Middle Eocene (orB. i. p. 222). 
 
 Lower Eocene. 
 Permian (or Zechstein). 
 Carboniferous. 
 Upper Devonian. 
 
 Permian (or Ivupfer-schiefer). 
 Carboniferous (Mountain Lime- 
 stone). 
 Devonian. 
 Upper Silurian. 
 
 Geographical Localities. 
 Paris (Gypsum of Mont- 
 
 martre). 1 
 Stonesfield. 2 
 Stuttgardt. 3 
 Paris (Gypsum .. Mont- 
 
 martre). 4 
 London (Sheppey Clay). 6 
 
 Thuringia. 6 
 
 Saarbruck, near Treves. 7 
 
 Elgin. 8 
 
 Thuringia. 9 
 
 Glasgow. 10 
 
 Caithness." 
 Ludlow." 
 
 I 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. 
 
 3 In 1818, Cuvier, visiting the Museum of Oxford, decided on the mammalian 
 character of a jaw from Stonesfield. See also above, p. 311. 
 
 3 Plieninger, Prof. See above, p. 340. 
 
 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"). 
 
 8 Owen, Prof., Geol. Trans. 2d 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 (P rotor osaurus Speneri, V. Meyer) was figured 
 by Spener, of Berlin, in 1810. (Miscel. Berlin.) 
 
 7 See above, p. 397. 
 
 8 See above, p. 412. _ 
 
 8 Memorabilia Saxonise Subterr., Leipsic, 1709. 
 
 10 History of Rutherglen, by Rev. David Ure, 1793. 
 
 II Sedgwick and Murchison, Geol. Trans. 2d Ser. vol. iii. p. 141, 1828. 
 12 Sir R. Murchison. See above, p. 431. 
 
 06s. The evidence derived from footprints, though often to be relied on, is 
 omitted 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, gener- 
 alized 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 successively, first to the Car- 
 boniferous, and then to the Upper Devonian periods. Before the year 
 1818, it was the popular belief that the Palseotherium of the Paris gyp- 
 sum and its associates were the first warm-blooded quadrupeds that ever 
 
CE. XXVIL] IN OLDER ROCKS. 457 
 
 trod the surface of this planet. 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 mam- 
 malian character of the relics. Even long after all controversy was set at 
 rect on these points, the real import of the new revelation, as bearing on 
 the doctrine of progressive development, was far from being duly appre- 
 ciated. 
 
 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 im- 
 agined, 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 crea- 
 tion of the placental tribes. Or, if when some monodelph were at last 
 actually recognized (at Stonesfield), 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 dis- 
 coveries alluded to arises from the aid they afford us in estimating the true 
 value of negative evidence, when brought to bear on certain speculative 
 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 hundred individuals in each generation, 
 and probably, when the species reached its maximum, several thousands. 
 When, therefore, we encounter for the first time in 1854 two or three 
 jaws of a Spalacotherium in the Purbeck limestone, after countless speci- 
 mens of Mollusca and Crustacea, and hundreds of insects, fish, and rep- 
 tiles 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 exist- 
 ence, 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 sheet was passing through the press 
 (Sept. 26, 1854) the discovery of another species of insectivorous mammal from 
 Stonesfield was announced to the British Association at Liverpool by Mr. Charles- 
 worth, who has given to it the name of Stereognathus ooliticus. It is more than 
 twice the size of any of the species previously obtained from the same formation, 
 "We have now, therefore, including the recently found Spalacotherium of Pur- 
 beck (see p. 295), five British mammalia from the oolite. 
 
458 VERTEBRATA IN THE [Cn. XXVII, 
 
 above table (p. 456), 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 mammalia 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. 212) ; 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, Pachyder- 
 mata, and Marsupialia (see p. 217). 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 recorded 
 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 im- 
 perfectly acquainted even with Great Britain), each class of Vertebrata 
 would probably recede one or more steps farther back into the abyss ot 
 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 devel- 
 opment 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 ichthyolites 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 man- 
 ner, 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 strata, wherein we can more 
 readily find deposits formed in lakes and estuaries. 
 
 * A bird's bone is recorded as having been lately found in the "Woolwich 
 beds (beneath the London clay), by Mr. Prestwich ; Geol. Quart. Journ. vol. x. 
 p. 157. 
 
CH. XXVII.J OLD FOSSILIFEROUS PERIODS. 459 
 
 The only incongruity between the geological results, and those which 
 our dredging experiences might have led us to anticipate a priori, con- 
 sists in the frequency of fossil reptiles, and the comparative scarcity of 
 mammalia. It would appear that during all the secondary periods, not 
 even excepting the newest part of the cretaceous, 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 geographical 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 mam- 
 malia 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 Vertebrata, 
 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. 401. 
 
4-60 TRAP EOCKS. rCH.XX.VUl 
 
 CHAPTER XXVIII. 
 
 VOLCANIC ROCKS. 
 
 Trap rocks K"ame, 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 Rocks, 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 
 volcanic 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 diagram, to represent 
 
 a. Hypogene formations, stratified and unstratified. 
 &. Aqueous formations. c. Volcanic rocks. 
 
 the crystalline formations, such as the granitic and metamorphic ; I 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 >, 
 sometimes overlying both, and occasionally alternating with the strata b b. 
 They also are seen, in some instances, to pass insensibly into the unstrati- 
 fied 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 entirely ignorant 
 of the phenomena of existing volcanoes. 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 nomencla- 
 ture 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 suc- 
 cession of terraces or steps on the sides of hills. This configuration 
 appears to be derived from two causes. First, the abrupt original ter- 
 minations 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. XXYIII] COXES AXD CRATERS. 461 
 
 ceased to flow, and grown solid, very commonly ends in a steep slope, 
 as at , fig. 620. But, secondly, the step-like appearance arises more 
 frequently from, the mode in which hori- 
 zontal 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 of limestone, and step-like appearance of trap, 
 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 be- 
 ginner 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 fossiliferous beds. The rock is occasion- 
 ally columnar, the columns sometimes 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 color, from the 
 oxidation of ferruginous matter, so abundant in the traps in which augite 
 or hornblende occurs ; or, in the felspathic varieties of trap, it acquires a 
 white opake coating, from the bleaching of the mineral called felspar. 
 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 been 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 disintegra- 
 tion. 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 calca- 
 reous 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 horn- 
 blende. (See Table, . p. 475.) 
 
 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 formations. Many hundreds 
 of these cones are seen in central France, in the ancient provinces of 
 
462 
 
 COMPOSITION AND NOMENCLATURE [On. XXVIII. 
 
 Auvergne, Velay, and Vivarais, where they observe, for the most part, a 
 linear arrangement, and form chains of hills. Although none of the 
 eruptions have happened within the historical era, the streams of lava 
 may still be traced distinctly descending from many of the craters, and 
 following the lowest levels of the existing valleys. The origin of the 
 
 Fig. 621. 
 
 Part of the chain of extinct volcanoes called the Monts Dome, Auvergne. (Scropc.) 
 
 cone and ciater-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 vapor, 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 enlargement of the included gases, and thus forms sconce, 
 other portions being reduced to an impalpable powder or dust. The 
 showering down of the various ejected materials round the orifice of erup- 
 tion 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 some- 
 times 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 volcanoes 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 volcanoes, see Principles of Geology, 
 chaps, xxiv. et seq. and xxxii. 
 
OH. XXVIIL] OF VOLCANIC ROCKS. 463 
 
 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 composed of two minerals, 
 or families of simple minerals, felspar and hornblende ; but the felspar 
 preponderates greatly even in those rocks to which the hornblendic min- 
 eral imparts its distinctive character and prevailing color. 
 
 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. 475) ; 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, but both the albitic and common felspar 
 appear sometimes 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, al- 
 though in some of them the one, and in others the other alkali greatly 
 prevails. 
 
 The hornblendic group consists principally of two varieties ; first, horn- 
 blende, 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 in- 
 structive. 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 mi- 
 nute quantity. In addition to these characters, it was remarked as a 
 geological fact, that augite and hornblende are very rarely associated to- 
 gether 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 crystalline slags of furnaces, augitic forms 
 
464 THEORY OF ISOMORPHISM. [On. XXVIII 
 
 were frequent, the liornblendic entirely absent ; hence it was conjec- 
 tured 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 hornblende. Lastly, Gustavus Rose fused a mass of horn- 
 blende 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 recognized 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 ex- 
 periments 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 demonstrate their absolute identity. 
 For there is often some portion of the materials in a crystal which are 
 not in perfect chemical combination with the rest. Carbonate of lime, 
 for example, sometimes carries with it a considerable quantity of silex 
 into its own form of crystal, the silex being mechanically mixed as 
 sand, and yet not preventing the carbonate of lime from assuming the 
 form proper to it. This is an extreme case, but in many others some 
 one or more of the ingredients in a crystal may be 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 de- 
 clared by skilful analyzers to be composed of distinct elements. (See 
 the table at p. 475.) This disagreement seemed at first subversive of 
 the atomic theory, or the doctrine that there is a fixed and constant re- 
 lation between the crystalline form and structure of a mineral and its 
 chemical composition. The apparent anomaly, however, which threat- 
 ened 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 that the composition of the min- 
 
Ca XXVIIL] PYEOXEXE AMPHIBOLE. 465 
 
 erals which had appeared so variable, was governed by a general law, to 
 which he gave the name of isomorphism (from itfo^, isos, equal, and M-op<p^, 
 morphe, form). According 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 
 ingredient Thus, in augite, the lime may be in part replaced by por- 
 tions 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 de- 
 fined limits. 
 
 Pyroxene, a name of Haiiy's, is often used for augite in descriptions 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 Hornblende 
 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 endeavor as soon as possible to familiarize himself with the char- 
 acters 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 ac- 
 ctistom the eye to know the appearance 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, fi-om 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 alone. If the felspar is in crystals, it is easily recog- 
 nized 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 goniometer 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 extremely 
 different from those of augite or hornblende ; so that the volcanic rocks 
 in which either of these minerals play a conspicuous part are easily re- 
 cognizable. 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 much uniformity of aspect and 
 
 30 
 
466 BASALT AUGITE TEACHYTE. [Ca XXVIII 
 
 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 fa- 
 miliar with this term than with that of any other kind of trap, it is dif- 
 ficult to define it, the name having been used so comprehensively, and 
 sometimes so vaguely. It has been generally applied to any trap rock 
 of a black, bluish, or leaden-gray color, having a uniform and compact 
 texture. Most strictly, it consists of an intimate mixture of felspar, augite, 
 and iron, to which a mineral of an olive-green color, 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, ac- 
 cording to Dr. Daubeny, in its more strict sense, is composed of " an in- 
 timate 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 distinctive character as con- 
 trasted 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,f 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. Am- 
 phibolite, 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 Analysis, p. 475), 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 ser- 
 pentine. 
 
 Trachyte. This name, derived from rpa^u^, 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 to M. Delesse it is variable in 
 
 * Volcanoes, 2d ed. p. 18. \ Mineralreich, 2d ed. p. 85. 
 
CH. XXVIIL] TRACHYTE PORPHYRY CLINKSTONE. 467 
 
 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 composi- 
 tion of trachyte, with quartz superadded, and without any augite or tita- 
 niferous 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 disseminated through a dark- 
 colored base. 
 
 Clinkstone, or Phonolite. Among the felspathic products of volcanic 
 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 gray- 
 ish blue or brownish color ; is variable in composition, 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. Ac- 
 cording to the analyses of Delesse and others, the chief cause of the green 
 color, in most greenstones, is not green hornblende nor augite, but a green 
 siliceous base, very variable and indefinite in its composition. The dark 
 color, 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 therefore pro- 
 posed that we should weigh these rocks, in order to appreciate their com- 
 position in cases where it is impossible to separate their component min- 
 erals. 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, con- 
 taining 69 per cent, of silica, a sp. gr. of only 2-58. If we then take 
 a rock of intermediate composition, such as that prevailing in the 
 Peak of Teneriffe, which Abich calls Trachyte-dolerite, its proportion of 
 silica being intermediate, or 58 per cent., it weighs 2'78, or more than 
 trachyte, and less than basalt.f The basalts are generally dark in color, 
 sometimes almost black, whereas the trachytes are gray, and even occa- 
 sionally white. As compared with the granitic rocks, basalts and tra- 
 chytes contain both of them more soda in their composition, the potash- 
 * Dr. Daubeny on Volcanoes, 2d ed. pp. 14, 15. f Ib id. 
 
468 FOKFHYRY AMYGDALOID. [Cs. XXYIIL 
 
 felspars being generally abundant in the granites. The volcanic rocks 
 moreover, whether basaltic or trachytic, contain less silica than the gra- 
 nites, in which last the excess of silica has gone to form quartz. This 
 mineral, so conspicuous in granite, is usually wanting in the volcanic for- 
 mations, 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 com- 
 position. 
 
 Porphyry is one of this class, and very characteristic of the volcanic 
 formations. When distinct crystals of one or more minerals are scattered 
 through an earthy or compact base, the rock is termed a porphyry (see 
 fig. 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, pitch- 
 stone porphyry, and so forth. The old 
 classical type of this form of rock is the 
 red porphyry of Egypt, or the well-known 
 " Rosso antico." It consists, according to 
 Delesse, of a red felspathic base in which 
 are disseminated rose-colored crystals of 
 the felspar called oligoclase, with some 
 plates of blackish hornblende and grains 
 of oxidized iron-ore (fer oligiste). Red 
 quartziferous porphyry is a much more 
 siliceous rock, containing about 70 or 80 mite ^ in a dark base 
 
 per Cent, of silex, while that of Egypt has of hornblende and felspar. 
 
 only 62 per cent. 
 
 Amygdaloid. This is also another form of igneous rock, admitting of 
 every variety of composition. It comprehends any rock in which round 
 or almond-shaped nodules of some mineral, such as agate, chalcedony, cal- 
 careous 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 
 
CH. XXVIIL] 
 
 LAVA SCORIJE PUMICE. 
 
 409 
 
 Fig.68a 
 
 Scoriaceous lava in part converted into an 
 
 amygdaloid. 
 
 Montagn e de la Veille, Department of Pay 
 de Dome, France. 
 
 are seen to have a glazed or vitreous coating, and in this respect exactly 
 resemble scoriaceous lavas, or the slags of furnaces. 
 
 The annexed figure represents a 
 fragment of stone taken from the 
 upper part of a sheet of basaltic lava 
 in Auvergne. One half is scoria- 
 ceous, the pores being perfectly emp- 
 ty; the other part is amygdaloidal, 
 the pores or cells being mostly filled 
 up with carbonate of lime, forming 
 white kernels. 
 
 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 occuss, formed 
 by the first thin sheet of liquid matter, which often precedes the main 
 current, 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 trachytic, as 
 in the Peak of Teneriffe ; a great number are basaltic, as in Vesuvius and 
 Auvergne ; others are Andesitie, 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.* 
 
 Scorice and Pumice may next be mentioned as porous rocks, pro- 
 duced by the action of gases on materials melted by volcanic heat. 
 Scorice are usually of a reddish-brown and black color, and are the 
 cinders and slags of basaltic or augitic lavas. Pumice is a light, spongy, 
 fibrous substance, produced by the action of gases on trachytic and other 
 
 * G. Rose, Ann. des Mines, torn, viii. p. 32. 
 
470 VOLCANIC TUFF PALAGCXNTTE TUFF. [On. XXVI1J. 
 
 lavas ; the relation, however, of its origin to the composition of lava is not 
 yet well understood. Von Buch says that it never occurs where only 
 Labrador-felspar is present. 
 
 Volcanic tuff, Trap tuff. Small angular fragments of the scoriae and 
 pumice, above mentioned, and the dust of the same, produced by volcanic 
 explosions, form the tuffs which abound in all regions of active vol- 
 canoes, 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. Besides the peculiarity of their composition, 
 some tuffs, or volcanic grits, as they have been termed, differ from ordi- 
 nary sandstones by the angularity of their grains, and they often fass 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 dis- 
 tinguished are usually brown, and the tuffs gray or white. 
 
 We meet occasionally with extremely compact beds of volcanic ma- 
 terials, interstratified with fossiliferous rocks. These may sometimes 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-colored 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 modem erup- 
 tions, 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 color, 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 vol- 
 canic tuffs. 
 
 * Geol. Trans. 2d series, vol. ii. p. 211. 
 
Cn. XXVm.] AGGLOMERATE LATERITE. 471 
 
 Agglomerate. In the neighborhood of volcanic vents, we frequently 
 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 expansive gases have forced their way. 
 The dispersion of such materials may be aided by the wind, as it varies 
 in direction or intensity, and by the slope of the cone down which they 
 roll, or by floods of rain, which often accompany eruptions. But if the 
 power of running water, or of the waves and currents of the sea, be suffi- 
 cient to carry the fragments to a distance, it can scarcely fail (unless 
 where ice intervenes) to wear off their .ingles, and \he formation then 
 becomes a conglomerate. If occasionally globular pieces of scoriae 
 abound in an agglomerate, they do not owe their rounded form to at- 
 trition. 
 
 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 aLgular 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 surfaoe- 
 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 colored by red ochre. As two of the lavas of the Giant's Causeway 
 are parted by a bed of lignite, it is not improbable that the layers of 
 laterite seen in the Antrim cliffs resulted from atmospheric decomposi- 
 tion. In Madeira and the Canary Islands, streams of lava of subaerial 
 origin are often divided by red bands of laterite, probably ancient soils 
 formed by the decomposition of the surfaces of lava-currents, many of 
 these soils having been colored red in the atmosphere by oxide of iron, 
 others burnt into a red brick by the overflowing of heated lavas. These 
 red bands are sometimes prismatic, the small prisms being at right angles 
 to the sheets of lava. Red clay or red marl, formed as above stated by 
 the 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 may have 
 
472 MINERAL COMPOSITION [On. XXVIIL 
 
 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 . f 
 volcanic vents, for the most part angular and without any admixture of 
 water-worn stones. " Volcanic conglomerates " may be applied to mix- 
 tures in which water-worn stones occur. 
 
 APHANITE. See Cornean. 
 
 AMPHIBOLITE, or HORNBLENDE ROCK, which see. 
 
 AMYGDALOID. A particular form of volcanic rock ; see p. 468. 
 
 AUGITE ROCK. A rock of the basaltic family, composed of felspar and augite. 
 See p. 466. 
 
 AUGITIC-PORPHYRY. Crystals of Labrador-felspar and of Augite, in a green or 
 dark gray base. (Rose, Ann. des Mines, torn. 8, p. 22, 1835.) 
 
 BASALT. An intimate mixture of felspar and augite with magnetic iron, olivine, 
 
 <fec. See p. 466. 
 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 color, like an indurated clay ; passes into hornstone ; generally 
 contains scattered crystals of felspar and sometimes of quartz. 
 
 CLINKSTONE. Syn. Phonolite, fissile Petrosilex, see p. 467 ; a grayish-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 
 Rocks, p. 481.) 
 
 CORNEAN or APHANITE. A compact homogeneous rock without a trace of crystal- 
 lization, breaking with a smooth surface like some compact basalts ; con- 
 sists 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. 
 
CH. XXVIII.] OF VOLCANIC EOCKS. 473 
 
 DIORITE. A kind of Greenstone, which see. Components, felspar and horn 
 blende in grains. According to Rose, Ann. des Mines, torn. 8, p. 4, dioritt 
 consists of albite and hornblende, but Delesse has shown that the felspar 
 may be Oligoclase or Labradorite. (Ann. des Mines, 1849, torn. 16, p. 
 323.) Its dark color is due to disseminated plates of hornblende. Set 
 above, p. 46*7. 
 
 DOLERITE. According to Rose (ibid. p. 32), its composition is black augite and 
 Labrador- felspar ; according to Leonhard (Mineralreick, <fcc., p. 77), augite, 
 Labrador-felspar, and magnetic iron. See above, p. 466. 
 
 DOMITS. 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 defined to be a mixture of augite 
 or hornblende and Saussurite, a mineral allied to jade. (Allan's 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. 467. 
 
 GRAYSTONE. (Graustein of Werner.) Lead-gray 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.) Graystone lavas are intermediate 
 
 in composition between basaltic and trachytic lavas. 
 
 HORNBLENDE RCCK, or AMPHIBOLITE. This rock, as defined by Leonhard, is com- 
 posed 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. 466. 
 
 HORNSTONE-PORPHYRY. A kind of felspar porphyry (Leonhard, loc. cit.) with a 
 base of hornstone, a mineral approaching near to flint, differing from com- 
 pact 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, 
 grayish, 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 hyparsthene 
 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 colored with red ochre. See 
 above, p. 471. 
 
 MELAPHYRE. A variety of black porphyry composed of Labrador-felspar and a 
 small quantity of augite. Its black color was formerly attributed to dis- 
 seminated microscopic crystals of augite, but M. Delesse has shown that 
 the paste is discolored 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 /ifAaj, melas, 
 black 
 
474 MINERAL COMPOSITION [On. XXVIIJ 
 
 OBSIDIAN. Vitreous lava like melted glass, nearly allied to pitchstone. 
 
 OPHIOLJ-FE. 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- 
 blende, and sometimes augite, occasionally of a green color, and passing 
 into serpentine. 
 
 PALAGONITE TUFF. An altered volcanic tuff containing the substance termed pa- 
 lagonite. See p. 470. 
 
 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. 470. 
 
 PETROSILEX. See Clinkstone and Compact Felspar. 
 
 PHONOLITE. Syn. of Clinkstone, which see. 
 
 PITCHSTONE, or KETINITE, 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 felepar (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. 469. 
 
 PrROXENic-PORPHYRT, same as augitic-porphyry, pyroxene being Haiiy's name for 
 augite. 
 
 SCORLE. Syn. volcanic cinders ; reddish brown or black porous form of lava. 
 See p. 469. 
 
 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 Ayalyses, p. 475), which forms veins in this rock. The mine- 
 rals most commonly found in Serpentine are diallage, garnet, chlorite, 
 oxydulous iron, and chromate of iron. The diallage and garnet occurring 
 in serpentine are richer in magnesia than when they are crystallized in 
 other rocks. (Delesse Ann. des Mines, 1851, torn, xviii. p. 309). Occurs 
 sometimes, though rarely, in dikes, altering the contiguous strata ; is in- 
 differently a member of the trappean or hypogene series. Its absence 
 from recent volcanic products seems to imply that it belongs properly to 
 the metamorphic class; and, even when it is found in dikes cutting 
 through aqueous formations, 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. 466. 
 
 TRAP TUFF. See p. 470. 
 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. 470. 
 
 VITREOUS LAVA. See Pitchstone and Obsidian. 
 VOLCANIC TUFF. See p. 470. 
 
 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. 
 
OH. XXVJII] 
 
 OF VOLCANIC EOCKS. 
 
 475 
 
 ANALYSIS OF MINERALS MOST ABUNDANT IN THE VOLCANIC AND 
 HYPOGENE ROCKS. 
 
 
 Silica 
 
 Alu- 
 mina 
 
 Mag- 
 ncsia. 
 
 Lime. 
 
 Potash. 
 
 Soda. 
 
 Iron 
 
 Oxide. 
 
 Man- 
 g-anese. 
 
 Remainder. 
 
 
 
 
 
 
 
 
 3- 
 10-80 
 
 1-00 
 
 43-05 C. 
 0-27 W. 
 12-20 W. 
 11-55 W. 
 8-96 W. 
 
 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. 
 
 1-63 T. 
 2-00 F. 
 1-58 F. 
 0-90 loss. 
 0-22 F. 
 1-51 loss. 
 3.59 L. 
 3-28 F. 
 
 0-11 P. 
 
 4-18 loss. 
 4;12 
 
 12-45 W. 
 13-70 W. 
 1070 W. 
 5-22 W. 
 5' W. 
 3-83 W. 
 
 0-12 P. 
 7-66 B. 
 2 -09 loss. 
 1-49 F. 
 0-22 Ph. 
 3-56 B. 
 0-41 L. 
 2-70 F. 
 1 3-77 loss. 
 C 4-02 B. 
 
 Actinolite (Bergman) ... 
 Augite, black, of volcanic rocks 
 (Klaprotb). 
 
 48-00 
 
 5-00 
 
 8-75 
 
 24-00 
 56-33 
 
 - ' 
 
 - - 
 
 Chiastolite (Landgrabe) - 
 Chlorite (Kobell) - 
 
 68-50 
 31-14 
 31-07 
 25-37 
 
 49-30 
 56-81 
 
 37' 
 6675 
 6491 
 68-84 
 71-50 
 
 58-91 
 
 55-75 
 53-20 
 
 63-25 
 62-87 
 35-75 
 
 30-11 
 17-14 
 15-47 
 28-79 
 
 5-50 
 2*07 
 
 21- 
 
 17-5 
 19-16 
 20-53 
 15-50 
 
 24-59 
 
 265 
 27-31 
 
 23-92 
 22-91 
 
 27-25 
 16- 
 12- 
 12-18 
 8-23 
 
 2-25 
 
 24-62 
 1-38 
 
 19-70 
 
 21-.y 
 
 11 -a 
 
 35- 
 12-67 
 13-92 
 19-80 
 
 33-61 
 33-03 
 
 0-25 
 0-42 
 0-92 
 
 33-09 
 
 41-83 
 34-75 
 
 1-13 
 34-40 
 19-14 
 17-09 
 
 17-61 
 29-68 
 
 0-65 
 0-50 
 0*40 
 
 i-oi 
 
 0-32 
 
 traces 
 
 
 
 
 
 
 
 
 3-85 
 19-99 
 28-79 
 
 9-43 
 8-46 
 
 24- 
 0-75 
 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. 
 5-03 P. 
 1-61 
 
 3-48 S. 
 11-72 
 12- 
 18-5 
 
 1-17 
 1-69 
 7-39 
 1-40 
 
 r ? 
 
 2.5 
 
 9-33 S. 
 6-19 P. 
 
 17-44 
 
 0-53 
 
 traces 
 
 0-51 
 0-62 
 
 1'5 
 
 0-25 
 
 0-25 
 0-22 
 traces 
 
 a trace 
 
 2-" 
 
 15-70 
 |l-09 
 
 o-io 
 
 1-40 
 
 traces 
 0-43 
 
 traces 
 
 1 
 
 97' S. 
 1-89 
 
 0-46 
 
 15-43 
 2-20 
 
 15- 
 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 
 
 
 trapp). 
 Diallage of euphotide (Delesse) 
 of bronzite from the Tyrol 
 (Kohler). 
 Epidote (Yauquelin) 
 Felspar, common (Rose) 
 
 
 AlDllC (rtOSCJ ^ ^ ^^ 
 
 the Vosges (Delesse). 
 
 the Tosges (Delesse). ' 
 
 ijuDrai jriic ^jYiaproinj 
 
 (Delesse). 
 
 from Mont Blanc (Delesse). 
 
 (Scheerer). 
 Garnet (Klaproth) .... 
 
 (Phillips) - 
 Hornblende (Klaproth) - 
 
 43' 
 42- 
 
 45-69 
 
 tj-m 
 
 54-25 
 5375 
 53-42 
 
 54-64 
 
 46-80 
 42.5 
 50- 
 
 40-00 
 41-22 
 37'54 
 
 49-06 
 
 46-23 
 40-86 
 50- 
 41-0 
 
 43-07 
 
 41-58 
 
 40-aa 
 
 M-85 
 
 64- 
 61-75 
 61-75 
 
 37-00 
 
 41*16 
 35-48 
 
 2-25 
 18'79 
 18-40 
 
 14- 
 
 14-95 
 
 9- 
 
 0-63 
 4-70 
 30-32 
 
 0-41 
 
 2-10 
 47-35 
 38-5 
 38-5 
 
 40-37 
 42-61 
 37-98 
 28-53 
 22- 
 31-68 
 30-5 
 
 2-58 
 
 0-61 
 4-68 
 
 20- 
 11- 
 13-85 
 7-05 
 
 1-5 
 21-72 
 
 1-61 
 9-87 
 
 1-33 
 
 2-58 
 0-70 
 
 0-25 
 
 a trace 
 0-14 
 
 2\-35 
 
 10-" 
 S'Bl 
 6-05 
 
 7-17 
 
 4-19 
 8-87 
 
 0-65 
 
 15-09 
 5-40 
 
 1-40 { 
 
 i-oo 
 
 1-45 
 
 ^P onsoor ) 
 
 from Corsica (Delesse). 
 Hypersthene (Klaproth) 
 Leucite (Klaproth) - 
 Malacolite or Sahlite, green (De- 
 lesse). 
 Mesotype (Gehlen) .... 
 (Berzelius) - 
 
 Mica (KlaprothT - 
 (Vauquelin) .... 
 
 black (H. Rose) 
 green, of protogine (Delesse) - 
 
 reddish, of crystalline lime- 
 stone (Delesse). 
 
 rose-colored, of granite (C. 
 Gmelin). 
 
 white, of pegmatite (Delesse) 
 Olivine (Berzelius) ... 
 (Klaproth) 
 
 roth). 
 Serpentine (Hi singer) 
 asbestitbrm (Delesse) 
 * common (Delesse) 
 Steatite (Delesse) ... 
 
 0-5 
 1-50 
 
 O'oO 
 
 275 
 065 
 
 2-17 
 0-48 
 
 1-39 
 
 1-37 
 1-75 
 
 Talc, pure (Delesse) 
 : (Klaproth) ... 
 
 Tourmaline or Schorl, black, of 
 granite from Devon (Rammels- 
 berg). 
 
 ravia (Rammelsberg). 
 Tourmaline (Gmelin) 
 
 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 th* 7th column of numbers, P. means Protoxide, and S. Sesquioxide. 
 
470 
 
 TKAP DIKES. 
 
 [Ca. XXLSL 
 
 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- 
 canoes 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 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 desciibe the manner and position 
 in which they occur in the earth's crust, and their external forms. The 
 leading varieties both of the basaltic aad trachytic rocks, as well as of 
 greenstone and the rest, are found sometimes in dikes penetrating strati- 
 fied 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 oc- 
 curring in all kinds of rocks, some a few feet, others many yards in width, 
 and often filled up with earth or angular pieces of stone, or with sand and 
 pebbles. Instead of such ma- 
 terials, suppose a quantity of Fig. 624. 
 melted stone to be driven or 
 injected into an open rent, and 
 there consolidated, we have then 
 a tabular mass resembling a 
 wall, and called a trap dike. 
 It is not uncommon to find such 
 dikes passing through strata of 
 soft materials, such as tuff, 
 scoriae, or shale, which, being 
 more perishable than the trap, 
 are often washed away by the 
 
 T_. i Bike in valley, near Brazen Head, Madeira. 
 
 6ea, rivers, Or ram, in which (From a drawing of Capt. Basil Hall, E. N.) 
 
CH. XXIX.] 
 
 TEAP DIKES AND VEINS. 
 
 477 
 
 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 greenstone of the dike is 
 usually more tough and hard than the 
 sandstone ; but chemical 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 as to resist the 
 action of the weather more than the dike 
 itself, or the surrounding rocks. When 
 this happens, two parallel walls of indu- 
 rated 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 common 
 in granite than in trap. The accompany- 
 ing sketch (fig. 626) by Dr. MacCulloch 
 represents part of a sea-cliff in Argyleshire, 
 where an overlying mass of trap, 6, sends 
 out some veins which terminate downwards. 
 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 
 
 Fissures left vacant by decomposed 
 trap. Strathaird, Skye. (MacCul- 
 loch.) 
 
 Fig. 626. 
 
 Trap veins in Airdnamurchan. 
 
 ramifying dike of greenstone, which I observed cutting through sandstone 
 on the beach near Kildonan Castle, in Arran. The larger branch varies 
 
 Fig. 627. 
 
 Ground plan of greenstone dike traversing sandstone. Arran. 
 
4YS VARIOUS FOEMS OF [On. XXIX. 
 
 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, prolonged 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. (MacCnlloch.) 
 
 Every variety of trap-rock is sometimes found in dikes, as basalt, green- 
 stone, 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 the dike is less crystalline 
 or more earthy than in the centre, in consequence of the melted matter 
 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 phenomena in Teneriffe, in the neighborhood 
 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 ver- 
 tical in its main direction, slightly flexuous, but 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 serpen- 
 tine is occasionally observed. On the left shore of the fiord of Christi- 
 ania, 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 of Naesodden, it 
 
CH. XXIX.] 
 
 TRAP DIKES AND VEINS. 
 
 479 
 
 Green- 
 stone. 
 
 Imbedded fragment of crystalline schist sur- 
 rounded by a band of greenstone. 
 
 enters mica-schist. Fig. 629 rep- Fi s- 6 ' 29 - 
 
 resents a ground plan, where the tic green^tone^of ^sodden, 
 
 dike appears 8 paces in width. In 
 
 the middle it is highly crystalline 
 
 and granitiform, of a purplish color, 
 
 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, 18 inches wide, of 
 
 dark greenstone. 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, 6, 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 
 
 one inch wide. 
 
 It seems therefore evident that the fragment, 6, has acted on the mat- 
 ter 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 granitiform syenite may 
 pass into ordinary rocks of the volcanic family. 
 
 The fact above alluded to, of a foreign fragment, such as 6, 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 uncommon. A fine 
 example is seen in another dike 
 of greenstone, 10 feet wide, in 
 the northern suburbs of Chris- 
 tiania, in Norway, of which the 
 annexed figure is a ground plan. 
 The dike passes through shale, 
 
 known bv its fossils to belono* Greenstone dike, with fragments of gneiss. 
 
 * Sorgenfria, Christiania. 
 
 to the Silurian series. In the 
 
 black base of greenstone are angular and roundish pieces of gneiss, some 
 white, others of a light flesh-color, some without lamination, like granite, 
 others with laminae, which, by their various and often opposite direc- 
 tions, show that they have been scattered at randon 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 
 
 Fig. 630. 
 
480 ROCKS ALTERED BY TRAP DIKES. [Cii. 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 (do- 
 lerite of some authors). Strata of shale and argillaceous limestone, 
 through which it cuts perpendicularly, are altered to a distance of 30, or 
 even, in some places, 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 converted into hard porcellanous jasper. In 
 the most hardened part of the mass the fossil shells, principally Producti, 
 are nearly obliterated ; 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 Product] . 
 The same mineral has been observed, under very analogous 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 some- 
 times extending 8 or 10 feet from the wall of the dike, being greatest 
 near the point of contact, and thence gradually decreasing 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 arenaceous ; a compact variety, having 
 a porcellanous aspect and a bluish-gray color, succeeds : this, towards the 
 outer edge, becomes yellowish-white, and insensibly graduates into the 
 unaltered chalk. The flints in the altered chalk usually assume a gray 
 yellowish color." All traces of organic remains are effaced in that part 
 of the limestone which -is most crystalline. 
 
 The annexed drawing (fig. 631) represents three basaltic dikes tra- 
 versing the chalk, all within the distance of 90 feet. The chalk contigu- 
 ous to the two outer dikes is converted into a finely granular marble, m m, 
 as are the whole of the masses between the outer dikes and the central 
 
 * Cambridge Transactions, vol. i. p. 402, f Ibid. vol. i. p. 410. 
 
 t Ibid. vol. ii. p. 175. 
 
 Dr. Berger Geol. Trans. 1st scries, vol. iii. p. 172. 
 
CH. XXIX.] ROCKS ALTERED BY TRAP DIKES. 
 
 Fig. 681. 
 
 481 
 
 Basaltic dikes in chalk in island of Eathlin, Antrim. 
 Ground plan, as seen on the beach. (Conybeare and Buckland.*) 
 
 one. The entire contrast in the composition and color of the intrusive 
 and invaded rocks, in these cases, renders the phenomena peculiarly clear 
 and interesting. 
 
 Another of the dikes of the northeast of Ireland has converted a mass 
 of red sandstone into hornstone. By another, the shale of the coal-meas- 
 ures 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. f 
 
 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 cin- 
 ders, and have all the character of coke ; while those close to it are con- 
 verted into a substance resembling soot.| 
 
 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 green- 
 stone 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 Crag, near 
 Edinburgh, a sandstone which comes in contact with greenstone is con- 
 verted 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 neighborhood of dikes are thus altered in 
 
 * Geol. Trans. 1st series, vol. iii. p. 210 and plate 10. 
 | Ibid. p. 213 ; and Playfair, Illust. of Hutt. Theory, s. 253. 
 $ Sedgwick, Camb. Trans. voL il p. 37. 
 Syst of Geol. vol. i. p. 206. 
 31 
 
INTRUSION OF TRAP BETWEEN STRATA. [Cn. XXIX 
 
 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 dis- 
 tricts, 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 entan- 
 gled 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 composi- 
 tion, structure, and the fractures which they may have experienced, and 
 perhaps, also, according to the quantity of water (so capable of being 
 heated) which they contain. It must happen in some cases that the com- 
 ponent 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 simply 
 filled with lava, which may begin to cool from the first ; whereas in 
 other cases the fissure may give passage to a current of melted matter, 
 which may ascend for days or months, feeding streams which are over- 
 flowing the country above, or are ejected in the shape of scoriae from 
 some crater. If the walls of a rent, moreover, are heated by hot vapor 
 before the lava rises, as we know may happen on the flanks of a volcano, 
 the additional 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 a, fig. 632, is in part 
 
 Fig. 682. 
 
 limestone and K~ti(il& 
 
 Trap interposed between displaced beds of limestone and shale, at White 
 Force, High Teesdale, Durham. (Sedgwick.*) 
 
 wedged in between the rocks of limestone, >, and shale, c, which have 
 been separated from the great mass of limestone and shale, J, with which 
 they were united. 
 
 * Camb. Trans, vol. ii. p. 180. 
 
CH. XXIX.] STKUCTUEE OF VOLCANIC EOCKS. 483 
 
 
 
 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 stratification 
 throughout large areas. They must in some places have forced their 
 way laterally between the divisions of the strata, a direction in which there 
 would 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 separable, 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 dis- 
 tances, like the joints in a vertebral column, as in the Giant's Causeway, 
 in Ireland. They vary exceedingly 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 isknd of StafFa. In a horizontal bed or sheet of trap the columns 
 are vertical ; in a vertical dike they are horizontal. Among other exam- 
 ples of the last-mentioned phenomenon is the mass of basalt, called the 
 Chimney, in St. Helena (see fig. 633), a pile of hexagonal prisms, 64 feet 
 
 Fig. 634 
 
 Small portion of the dyke 
 in Fig. 638. 
 
 Yolcanic dyke composed of hori- 
 zontal prisms. St. Helena. 
 
 high, evidently the remainder of a narrow dike, the walls of rock which 
 the dike originally traversed having been removed down to the level of 
 
 * MacCuL Sys. of GeoL voL ii. p. 137. 
 
484 
 
 STRUCTURE OF VOLCANIC ROCKS. 
 
 [On. XXIX. 
 
 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 sur- 
 faces. If these surfaces, therefore, instead of being either perpendicular 
 or horizontal, are curved, the columns ought to be inclined at every 
 angle to the horizon ; and there is a beautiful exemplification of this 
 phenomenon in one of the valleys of the Vivarais, a 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 scorise. From the crater of one of these cones, called La Coupe 
 d'Ayzac, a stream of lava descends and occupies the bottom of a nar- 
 row valley, except at those points where the river Volant, or the torrents 
 which join it, have cut away portions of the solid lava. The accom- 
 panying sketch (fig. 635) represents the remnant of the lava at one of 
 
 Fig. 635. 
 
 Lava of La Coupe d'Ayzac, new- Autraigue, in the province of Ardeche. 
 
 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 gradually swept away all below that line, 
 while the tributary torrent has laid open a transverse section ; by which 
 we perceive, in the first place, that the lava is composed, as usual in this 
 country, of three parts : the uppermost, at a, being scoriaceous ; the 
 second, 6, presenting irregular prisms ; and the third, c, with regular col- 
 umns, 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 ^, 
 and are horizontal at/, their position having been everywhere determined, 
 according to the law before mentioned, by the concave form of the origi- 
 nal valley. 
 
 In the annexed figure (636) a view is given of some of the inclined and 
 curved columns which present themselves on the sides of the valleys in 
 the hilly region north of Vicenza, in Italy, and at the foot of the higher 
 Alps.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. 
 
 * Seale's Geognosy of St. Helena, plate 9. 
 
 \ Fortis. M6m. sur 1'Hist. Nat. de 1'Italie, torn. i. p. 283, plate 7. 
 
OIL XXIX.] 
 
 STRUCTURE OF VOLCANIC ROCKS. 
 
 85 
 
 The columnar structure is by no means Fi s- 636 - 
 
 peculiar to the trap rocks in which augite 
 abounds ; it is also observed in clinkstone, 
 tractate, and other felspathic rocks of the 
 igneous class, although in these it is rarely 
 exhibited in such regular 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 Bert- 
 rich-Baden, in the Eifel, near the Moselle 
 (fig. 637). The basalt there is part of a 
 small stream of lava, froin 30 to 40 feet thick, which has proceeded from 
 one of several volcanic craters, still extant, on the neighboring heights. 
 
 Fig. 637, 
 
 Columnar basalt in tho Vicentin. 
 (F<\rtis.) 
 
 Basaltic pillars of the Kasegrotte, Bertrich-Baden, halfway between Troves and Coblentz. 
 Height of grotto, from 7 to 8 feet 
 
 The position of the lava bordering the river in this valley might be repre- 
 sented by a section like that already given at fig. 635, if we merely sup- 
 posed inclined strata of slate and the argillaceous sandstone called grey- 
 wacke 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 crystallization, around 
 which the different minerals of the rock arranged themselves symmetri- 
 cally 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, sur les Roches Globuleuses, Mem. de la Soc. G6ol. de France, 2 ser. 
 torn. iv. 
 
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 decomposi- 
 tion, " and when the balls," says Mr. Scrope, 
 "have been exposed a short time to the 
 .weather, they scale off at a touch into nu- 
 merous concentric 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 application of a ruder blow will pro- 
 duce 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 arrangements are 
 very obscure, but are supposed to be con- 
 nected with changes of temperature during 
 the cooling of the mass, as will be pointed out in the sequel. (See chaps. 
 xxxv. and xxxvi.) 
 
 Globiform pitchstone. Chiaja di 
 Luna, Isle of Ponza. (Scrope.) 
 
 Relation of Trappean RocJcs to the products of active Volcanoes. 
 
 When we reflect on the changes above described in the strata near 
 their contact with trap dikes, and consider how complete is the analogy 
 or often identity in composition and structure of the rocks called trappean 
 and the lavas of active volcanoes, it seems difficult at first to understand 
 how 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 subterranean igneous action were contrasted with loose cones of scoriae, 
 tuff, and lava, or with narrow streams of lava in great part scoriaceous 
 and porous, such as were observed to have proceeded from Vesuvius and 
 Etna, the resemblance seemed remote and equivocal. It was, in truth, 
 
 * Scrope, Geol. Trans. 2d series, vol. ii. p. 205. 
 
CH. XXIX.] LAVA, AND SCORLE. 487 
 
 like comparing the roots of a tree with its leaves and branches, which, 
 although they belong to the same plant, differ in form, texture, color, 
 mode of growth, and position. The 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 
 ^Etherias, tantum radice in Tartara tendit," 
 
 for its roots do literally reaca downwards to Tartarus, or to the re- 
 gions 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 destruc- 
 tion of whatever may once have formed the 
 uppermost part of ancient submarine or sub- 
 aerial volcanoes, more especially as those 
 superficial parts are always of the lightest 
 and most perishable materials. The abrupt 
 manner in which dikes of trap usually ter- 
 minate at the surface (see fig. 639), and 
 the water-worn pebbles of trap in the allu- 
 vium which covers the dike, prove incon- 
 testably that whatever was uppermost in 
 these formations has been swept away. It is easy, therefore, to conceive 
 that what is gone in regions of trap may have corresponded to what is 
 now visible in active volcanoes. 
 
 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 counterparts must 
 be sought in the products of modern submarine volcanic eruptions. 
 If it be objected that we have no opportunity of studying these last, 
 it may be answered, that subterranean movements have caused, al- 
 most everywhere in regions of active volcanoes, great changes in the 
 relative level of land and sea, in times comparatively modern, so as 
 to expose to view the effects of volcanic operations at the bottom of 
 the sea. 
 
 Thus, for example, the examination of the igneous rocks of Sicily, 
 especially those of the Val di Noto, has proved that all the more ordi- 
 nary varieties of European trap have been there produced under the 
 waters of the sea, at a modern period ; that is to say, since the Mediter- 
 ranean has been inhabited by a great proportion of the existing species of 
 testacea. 
 
488 KELATION OF TRAP, [Cn. XXIX 
 
 These igneous rocks of the Yal di Noto, and the more ancient trappear. 
 rocks of Scotland and other countries, differ from subaerial volcanic for- 
 mations in being more compact and heavy, and in forming sometimes 
 extensive sheets of matter intercalated between marine strata, and some- 
 times 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 Yal di Noto ; and that they were removed by the waves, 
 in the same manner as the cone of Graham Island, in the Mediterra- 
 nean, 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 ma- 
 terials first scattered far and wide by the winds and waves, and then de- 
 posited. 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 be- 
 comes land. The proportion of volcanic matter which is originally sub- 
 marine 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 conti- 
 nents, near the shore. 
 
 As to the absence of porosity in the trappean formations, the appear- 
 ances 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. 469) ; 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 characteristic of the pores of 
 slaggy lavas. Even in some parts of this rock which are excluded from 
 air and water, the cells are empty, and seem to have always remained 
 in this state, and are therefore undistinguishable from some modern 
 lavas.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." J The same 
 author also considers it not improbable that some of the volcanic 
 
 * See Princ. of Geol., Index, " Graham Island," "Fyoe," "Conglomerates, vol- 
 canic," &c. 
 
 f MacCulloch, West Islands, voL iL p. 487. 
 i Syst of Geol. vol. ii. p. 114. 
 
CH. XXIX.] LAVA, AND SCORIAE. 489 
 
 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 33d 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 allu- 
 ded to in the last chapter (p. 462), and more fully explained in the 
 " Principles of Geology" (chaps, xxiv. to xxvii.), where Vesuvius, Etna, 
 Santorin, and Barren Island are described. The more ancient portions of 
 those mountains or islands, formed long before the times of history, ex- 
 hibit the same external features and internal structure which belong to 
 most of the extinct volcanoes of still higher antiquity ; and these last have 
 evidently been due to a complicated series of operations, varied in kind 
 according to circumstances : as, for example, whether the accumulation 
 took place above or below the level of the sea ; whether the lava issued 
 from one or several contiguous vents.; and, lastly, 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 con- 
 sidered in this chapter. 
 
 Craters and Calderas, Sandioich 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 volcanoes of the Sandwich 
 Islands, Mounts Loa and Kea in Owyhee, are huge flattened volcanic 
 cones, about 14,000 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 to the cone, down slopes varying 
 
 * Syst. of Geol. voL ii. p. 114. 
 
490 EXTERNAL FORM, STRUCTURE, AND 'ORIGIN [On. XXIX, 
 
 Fig. 640. 
 
 Mount Loa, in the Sandwich Islands. (Dana.) 
 
 a. Crater at the summit. &. The lateral crater of Kilauea. 
 
 The dotted lines indicate a supposed column of solid rock caused by the lava consolidating after 
 
 eruptions. 
 
 on an average from 4 degrees to 8 degrees ; but in some places consider- 
 ably 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, 6, 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 recognized by the emission of a vivid light from the 
 bottom of an ancient 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 com- 
 mencement 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.] OF VOLCANIC MOUNTAINS. 491 
 
 Thus in the same volcano examples are afforded of the overflowing of 
 lava from the summit of a cone 2| miles high, and of the underflowing ot 
 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 in- 
 stance, 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 about 7500 feet 
 
 Fig. 641. 
 
 b 
 
 Section of the crater of Kilauea in the Sandwich Islands. (Dana.) 
 a, &. External boundaries of the chasm in the line of its shortest diameter, 
 c, <?,/, d. Black ledge. g, A. Lake of lava. 
 
 long. The boundary cliffs, a, c and 6, rf, are for the most part quite 
 vertical and 650 feet high. They are composed of compact rock in 
 layers, not divided by scoriaB, 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 /, c?, composed of similar stratified 
 materials. This ledge is 342 feet in height above the lake of lava, <7, A, 
 which it encircles. The chasm, a, 6, 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 
 /, 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 perpen- 
 dicular, which have occurred in the neighborhood 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, a, fig. 640, must be great and must create a ten- 
 dency 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 the pressure 
 
492 ISLAND OF JAVA. [Cu. XXIX. 
 
 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 eruption is sur- 
 rounded by the ruins of a larger and older cone, usually presenting a 
 crescent-shaped precipice towards the newer cone. In volcanoes 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 be- 
 tween the older and newer cone, and the cavity may thereby be pro- 
 longed downwards, and end in a ravine. In such cases it may be impos- 
 sible 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 engulfment and denudation. 
 
 Java. One of the latest contributions to cjr knowledge of volcanoes 
 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 internal 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 sub- 
 aerial 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 re- 
 duced to 10 and often 4 or 5 degrees.* The interference of the lavas 
 of adjoining volcanoes sometimes produces elevated platforms, or " sad- 
 dles," 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, hekleeding en invendige structuur, door F. Jung- 
 htihn. (German translation of 2d edit, by Hasskarl, Leipzic, 1852.) 
 
CH. XXIX.] JAVANESE CALDERAS. 493 
 
 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 Span- 
 iards 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 subsidence 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 sum- 
 mit in 1772 ; but affirms that most of the towns on its sides said to have 
 been engulfed 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 mountain'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 between these furrows, are very con- 
 spicuous, 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 betause 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 engulfment, it may remain uninjured 
 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 super- 
 ficial scoriae and lavas decompose and become covered with clayey soils, 
 the erosive action of water begins to operate with a prodigious force, 
 proportionate to the steepness of the declivities and the incoherent nature 
 of the sand and ashes. Even the more solid lavas are occasionally cavern 
 
 * See Principles of GeoL 9th edit. p. 493. 
 
494: 
 
 CANARY ISLANDS. 
 
 rcn. xxix. 
 
 Fig. 642. 
 
 ous, and almost always alternate with scoriae and perishable tuffs, so as to 
 be readily undermined, and most of them are speedily reduced to frag- 
 ments of a transportable size because they are divided by vertical joints 
 or split into columns. 
 
 Canary Islands Palma. I have enlarged so fully in the " Principles 
 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 chap- 
 ter 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-laborer, 
 Mr. Hartung, of Konigsberg. We visited among other places the beau- 
 tiful 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 46 geographical miles west of TenerifTe. Seen from the chan- 
 nel which divides the two islands, 
 Palma appears to consist of two 
 principal mountain masses, the de- 
 pression 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 nor- 
 thern of these masses makes, not- 
 withstanding 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 inhabitants 
 "La Caldera." This cavity (6, c, 
 d, e, fig. 642) is from 3 to 4 geo- 
 graphical miles in diameter, and 
 the range of precipices surrounding 
 it vary from about 1500 to 2000 
 feet in vertical height. From their base a steep slope, clothed by a 
 splendid forest of pines, descends for a thousand and sometimes two thou- 
 sand 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 as they 
 approach the lower country. A great number of ravines commence on 
 
 ff 
 
 =a 
 
 Geogr. Miles. 
 
 Fuencaliente Pt. 
 
 Map of Palma, from Survey of Capt. Vidal, E. K 
 
 * Erhebung's Crater. 
 
CH. XXIX.] 
 
 CALDERA OF PALMA. 
 
 495 
 
 the flanks of the mountain, a short distance below the summit, shallow 
 at first, but getting deeper as they descend, and becoming at the same 
 time more numerous, as in the cones of Java before mentioned. 
 
 So unbroken is the precipitous boundary-wall of the Caldera, except at 
 its southeastern end, where the torrent which drains it through a deep 
 gorge (6, &', fig. 643), issues, 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. 494). 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 pails 
 of the Caldera, the vertical precipices join the talus-like, rocky slope, cov- 
 ered with pines. The other or principal entrance by which the Caldera 
 is drained, is the great ravine or barranco, as it is called (see 6, &', fig. 643), 
 which extends from the southwestern extremity of the Caldera to the sea, 
 
 Fig. 64a 
 
 Map of the Caldera of Palma and the great ravine, called "Barranco de las Angustias.'' 
 the Survey of Capt Tidal, E. N., 1S37. Scale, two geographical miles to an inch. 
 
 From 
 
496 
 
 ISLAND OF PALMA. 
 
 [Cn. XXIX. 
 
 a distance of 4J geographical miles, in which space the water of the tor- 
 rent falls about 1500 feet. 
 
 Fig. 644. 
 
 View of the Isle of Palma, and of the entrance into the central cavity or Caldera. From 
 Von Buch's " Canary Islands." 
 
 This sketch was taken by Yon 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 in- 
 ferred from this sketch. 
 
 The annexed section (fig. 645) passes through the island from Santa 
 Cruz de Palma to Briera Point, or from southeast to northwest (see 
 map, p. 494). It has been drawn up on a true scale of heights and 
 horizontal distances from the observations of Mr. Hartung and my own. 
 
 S.P. a, 
 
 Section of the Island of Palma, from Point Briera, on the northwest, to Santa Cruz de Palma, on 
 the southeast See map, fig. 642, p. 494. 
 
 a, &. 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. 
 8. 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 start- 
 ing 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 6, where 
 dikes abound. 
 
CH.XXIX.] 
 
 SECTION OF ISLAND OF PALMA. 
 
 497 
 
 fti 
 
 5 
 
 fi's^ llvj 
 
 is^gslki 
 l^lPsi 
 
 32 
 
'.498 STRUCTURE AND ORIGIN OF THE [On. 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 southwest. 
 
 The lowest of the two slanting lines, m, f, descending from the Caldera 
 to the sea along the bottom of the Barranco, represents the present bed 
 of the torrent ; the upper line, &, Z, the height at which beds of gravel, 
 elevated high above the present river-channel, are visible in detached 
 patches, shown by dotted spaces at &, and to the southwest of it, on the 
 same slope. These, and the continuous stratified gravel and conglomer- 
 ate lower down at I and *, 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 perpen- 
 dicular dikes which abound there. Countless others, inclined and tor- 
 tuous, are found penetrating the same rocks. The five outliers of some- 
 what 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 
 engulfment, 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 formations. 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 right 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 half or a quar- 
 ter of a mile, and usually sooner. Coarse breccias or agglomerates pre- 
 dominate in the lower part, as if the commencement of the second series 
 of rocks marked an era of violent gaseous explosions. Single beds of this 
 aggregate of angular stones and scoriaB attain a thickness of from 200 to 
 300 feet. They are united together by a paste of volcanic dust or spongi- 
 form 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-colored 
 scoriae are as twisted and ropy as any to be seen on the slopes of 
 Vesuvius ; seeming to imply that there was here an ancient vent or 
 
CH. XXIX.] CALDEEA OF PALMA. 499 
 
 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 ter- 
 minating 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 agglomerate 
 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 attri- 
 tion. 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 coextensive with the Caldera and the vol- 
 canic 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 diame- 
 ter, 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'), espe- 
 cially 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 color from the upper, exhibit- 
 ing a tea-green and in parts a light yellow tint, instead of the usual 
 brown, lead-colored, or reddish hues of basalt and its associated scoriae. 
 Beds of a light greenish tuff are common, together with trachytic and 
 greenstone rocks, the whole so reticulated 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 (c?, figs. pp. 494 and 497) 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 arrange- 
 ment, exhibiting first a southerly and then a northerly dip at angles 
 varying from 20 to 40 degrees (see section, fig. 646 at &). Hence 
 we may presume that the older strata must have undergone great 
 movements before the upper formation was superimposed. No or- 
 ganic 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 erup- 
 tions, 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 semi-crystalline and almost metamorphic 
 character. 
 
 The existence of so great a mass of volcanic rocks of ancient dat6 
 
500 CALDERA OF PALMA. [Cn. XXIX 
 
 on the exact site of an equally vast accumulation of comparatively mod- 
 ern lavas and scoriae is peculiarly worthy of notice as a general phenome- 
 non observed in very different parts of the globe. It proves that, 
 notwithstanding the fact in the past history of volcanoes 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 per- 
 sistent for more than one geological period in the same place, relaxing 
 perhaps in 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 beginning, 
 having grown by the superposition of one conical envelope of lava and 
 ashes formed over another, or whether, as Yon 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 move- 
 ments 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 Cra- 
 ters" 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, engulfment, and aqueous denu- 
 dation. 
 
 The favorable 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 origi- 
 nally 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, scoria3, 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 advanced 
 
CH. XXIX.] HYPOTHESIS OF UPHEAVAL. ' 501 
 
 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 disloca- 
 tions 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 sc ^ar to ob- 
 literate the great cavity. 
 
 The second objection is the impossibility of imagining that so vast 
 a series of agglomerates, tuffs, stratified lapilli, and highly scoriaceous 
 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 per- 
 fect accordance with this hypothesis that we should behold agglomerates, 
 lapilli, and scoriae predominating in the walls of the Caldera ; whereas 
 in the ravines nearer the sea, where the inclination of the beds has di- 
 minished to 10 and even to 5 degrees, the proportion of stony as com- 
 pared to fragmentary materials 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 b, fig. 645, p. 496 ; 
 while the dikes are few in number where the stony lavas predominate 
 (as at c, ibid.). Many of the scoriaceous beds at 6 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 scoriaB and lapilli. But unfortunately no one can climb up and de- 
 termine how far the supposed parallelism may be deceptive. The solid 
 
502 STONY LAVAS FORMED ON SLOPES. [Cn. XXIX. 
 
 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. Neverthe- 
 less 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. 511), 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 down- 
 ward 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 volcanoes, and that they acquired subsequently a steeper inclina- 
 tion. 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 composition, 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 Palrna must be enormous ; so that, 
 could it be withdrawn, 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 conformed to surfaces already inclined 
 at angles of 20, or, in the case of the Caldera of Palma, 28 degrees. 
 
CH. XXIX.] AQUEOUS EROSION IX PALMA. 503 
 
 For this reason the defenders of the upheaval hypothesis are consistent 
 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 subterranean force is repre- 
 sented 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 characteristic of the antecedent volcanic phe- 
 nomena. 
 
 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 
 Tenerifie, 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 northeast of Fuencaliente 
 at the southern extremity of Palma, so modem 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 solidi- 
 fied 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 enveloping crust of scoriae at the lower end of a 
 lava-current in which one of these tunnels existed may have been suf- 
 ficient 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 dis- 
 tinct 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 man- 
 ner before suggested, to what extent has its shape been subsequently 
 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 sec- 
 tion, pp. 49*7, 498). 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 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 
 
504: EXTENT AND NATURE OF [On. XXIX. 
 
 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 contemporaneous 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 immedi- 
 ately adjoining the Barranco, like the cone of Argual (see map, p. 495) 
 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 westward, 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 &', may be more considerable, but cannot be ascertained, 
 as it is concealed under modern scoriae and lava spread over the great 
 platform, F. 
 
 Fig. 64T. 
 
 East 
 
 A. Ravine or Barranco de las Angustias, near its termination in Palma. 
 Z>, &', &". Conglomerate, 800 feet thick in parts. 
 
 c, e'. Lava intercalated between the beds of conglomerate. 
 
 d, d'. Another and older current of basaltic lava, columnar in parts. 
 
 E. Cliff of ancient volcanic rocks of the Upper Formation (p. 500), 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. 497. 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 transport- 
 ing agent, it is obvious that a large portion of the volcanic materials, 
 consisting of sand, lapilli, and scoriae, before described (p. 498), as be- 
 
CH. XXIX.] AQUEOUS EROSION" IN PALMA. 505 
 
 longing 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 peb- 
 bles, must have lost more than half their original bulk, and bear witness 
 to large quantities of sedimentary 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 there- 
 fore no doubt that the erosive power even of rain and river water, aided 
 by earthquakes, 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 volcanic action, because they forcibly reminded me of the precipices 
 encircling three sides of the Val de Bove, on Etna ; and because they 
 agree so well with Junghuhn's description of the "old crater-walls" 
 of active volcanoes in Java, some of which equal or surpass in dimen- 
 sions even the Caldera of Palma. The latter may have consisted 
 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 define how much 
 of the work has been accomplished by aqueous, and how much by vol- 
 canic 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 countries, and I need not dwell 
 here on its interpretation, but refer to what was said in the 7th chap- 
 ter. (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. 509), 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 original 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, provided they 
 enable us to explain more naturally than by any other causation, the 
 
506 EXTENT AXD NATURE OF [Ca XXTX. 
 
 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 argu- 
 ment 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 re- 
 garded 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. 504, already mentioned, and c,/, map, p. 494, extending four or five 
 miles from the Caldera to the sea on the right bank of the Barrranco, 
 and no cliff of corresponding height or structure on the other bank, 
 where for miles towards the southeast there is the platform F, fig. p. 504, 
 supporting several minor volcanic cones. The sea might be supposed to 
 leave just such a cliff as E, after cutting away a portion of the southwest- 
 ern 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 con- 
 glomerate ascending an inclined plane, *, I, Jfc, p. 497, from the sea-level 
 to an elevation of about 1500 feet, near the entrance of the Caldera, this 
 is by no means conclusive in favor of fluviatile action, although some ele- 
 vated 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 favor 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. 497), forming a 
 notch in the uppermost line of precipices surrounding the Caldera. 
 This break divides the mountain called Alejanado, </, fig. p. 497, from 
 the eastern wall c, /, and cuts quite through the upper formation ; yet 
 the range of precipice /, e, on the eastern side of the Caldera is con- 
 tinued uninterruptedly, and retains its full height of 1500 or 2000 feet 
 above its base, to the southward 6f the Cumbrecito, or from e towards a, 
 map, fig. 642, p. 494. In this prolongation 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. 497, 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 or 
 a fault the lower formation would not be persistent and uninterrupted 
 across the Cumbrecito, constituting the watershed ; . but would have 
 sunk down and have been replaced by the upper basaltic rocks. If 
 * Geolog. Obaerv., South America, p. 43. 
 
CH. XXIX.] AQUEOUS EROSION IX PALMA. 507 
 
 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 f, 
 and such an extension of the line of cliffs as that now observable 
 between e and a, map, p. 494, 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 ma- 
 rine 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 ob- 
 serve 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 Bar- 
 ranco 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 Caldera, 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 Bar- 
 ranco 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 contemporaneous 
 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 con- 
 glomerate 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. 496. 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 dis- 
 play no superficial signs of marine denudation, every old beach or delta 
 once at the mouth of a torrent being concealed under newer volcanic out- 
 pourings. 
 
 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. 494 ; one of the volcanoes in this 
 range, called Verigojo, g, being no less than 6565 English feet high. 
 The lavas descending from several vents in this chain reach the sea both 
 
508 
 
 ISLAND OF ST. PAUL. 
 
 [Cn. XXIX. 
 
 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 vol- 
 canic vents to assume a linear arrangement, as seen in the volcanoes 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 sub- 
 terranean 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 obser- 
 vations are required to explain the structure and configuration of such 
 volcanic islands. It may be useful to cite, in illustration of the same sub- 
 ject, 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. 648. 
 
 Map of the Island of St. Paul, in the Indian Ocean, lat. 38 44' S., long. 77 37' E., 
 surveyed by Capt. Blackwood, E. 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 ex- 
 emplifies a class of insular volcanoes into which the ocean now enters by 
 
CttXXIX.] ISLAND OF ST. PAUL. TEXERIFFE. 509 
 
 Fig. 649. 
 
 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 distmnt 
 (Captain Blackwood.) 
 
 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 pas- 
 sage 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, whenever considerable oscillations in the relative level 
 of land and sea have occurred. 
 
 Peak of Teneri/e. The accompanying view of the Peak, taken from 
 sketches made by Mr. Hartung and myself during our visit to Teneriffe 
 
510 
 
 VIEW OF PEAK OF TENERIFFE. 
 
 [Cn. XXIX. 
 
 II, 
 
 *" rf 
 I s 
 
 a s 
 
 o A., 
 S cSi 
 
 
 ^"^? 
 
CH. XXIX.] PEAK OF TEXERIFFE. 511 
 
 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 pre- 
 cisely 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 6, 
 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 6, 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, d d, have also flowed down from lateral openings, es- 
 pecially from a crater called the Chahorra,/, 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. 
 
 s. w. N. E. 
 
 Section through part of Teneriffe, from N. E. to 8. W. On a true scale ; as given in 
 Von Bnch's " Canary Islands." 
 
 a. Peak of Teneriffe. J. The Canadas or atrium. 
 
 c. Cliff bounding the atrium. d. Modern lavas. 
 
 f. Cone and crater of Chahorra. 
 
 To what extent the lavas, d d, figs. 651, and 652, may have narrowed 
 the circus or atrium, 6, 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 volcanoes 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 southwestern 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 geo- 
 logical 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, inas- 
 much as both consist mainly of basaltic rocks of subaerial 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 origin, 
 
512 ISLAND OF MADEIEA. [On. XXIX. 
 
 and referable perhaps to the Miocene tertiary epoch. Tuffs and lime- 
 stones containing marine shells and corals occur at S. Vicente 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 ag- 
 glomerates 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 com- 
 prehend 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 accumu- 
 lation 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 of the 
 volcanic mass, below / h and e g, 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 accumulation of scoria?, 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 scoriaB. 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 juxtaposition of such a 
 multitude of cones or points of eruption, and the interference of their 
 
CH. XXIX.] 
 
 SECTION OF MADEIRA. 
 
 513 
 
 Iliitt 
 
 r? f ?r 
 
314 FOSSIL PLANTS OF MADEIRA. [On. XXIX, 
 
 lavas along the great east and west line of volcanic action, that wo 
 find the stony beds in the central region between e and /, 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 de Serra (or, fig. p. 516). 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 
 / 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 J, as at K, near 
 Funchal. In this latter characteristic, however (tie 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 <?, fig. 653, which have been overwhelmed by lavas flowing from the 
 central region. The aggregate thickness of the more solid basalts alter- 
 nating with tuffs rarely exceeds 1500 feet ; but below Pico S. Antonio, 
 or K, fig., p. 513, they attain a thickness of 3000 feet, being exposed to 
 view on the sides of a deep valley called the Curral, presently to be 
 mentioned. 
 
 As a general rule, the lavas of Madeira, whether vesicular or compact, 
 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 
 1 840, having met with the carbonized branches and roots of shrubs in 
 some red clays under basalt near Funchal. Nevertheless, 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 im- 
 pure 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 dicotyledonous 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 ap- 
 parently of the myrtle family, the larger proportion having their surfaces 
 
Cn. XXIX.] CRATER OF LAGOA. 515 
 
 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 be- 
 tween the ancient vegetable remains and the modern forests of Ma- 
 deira, in which laurels and other evergreens abound, with glossy cori 
 aceous and entire-edged leaves, while below them there is an under- 
 growth 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 superimposed 
 basalts and scoria3, 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 whortleberry ( Vacciniwn 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 
 
516 CENTRAL VALLEYS. [Cn. 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 deter- 
 mined, since it is exposed to view for too short a distance ; 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, however, 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, are separated by a narrow and lofty ridge, c, part of 
 
 "West. East. 
 
 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. 
 
 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 superfi- 
 cial volcanic action. 
 
 In the Alps, no doubt, as in other lofty chains, the formation of val- 
 leys 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.] TRACKYTIC KOCKS. 517 
 
 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. 475, support a single torrent so long as eruptions were frequent on its 
 slopes. The period, therefore, of fluviatile erosion must have been sub- 
 sequent to the formation of the central nucleus of ejectamenta, c, fig., 
 p. 513, and of the lavas, c?, ibid. When we infer that these were of 
 supramarine origin as far down as the line p, , 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 subject of specula- 
 tion ; and whether the steep dip of the lavas seen in the ravines inter- 
 secting the slopes of the mountain, / h and e g, can be ascribed 1 o 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 succession. Near Porto da Cruz, for example, on the northern 
 coast, trachytes of a gray, and trachytic tuffs almost of a white color, 
 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. 513, lie buried. During the 
 convulsions which accompanied the outpouring 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 out- 
 pourings. So also on the southern 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 occupying the highest geological position. They consist of 
 white and gray 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. 513, 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. 522), is by no means borne out in 
 
518 LAVAS OF MADEIRA. ' [Cu. XXIX. 
 
 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 examining 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. 513, 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, e~xn 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 Pal ma (p. 508) of 
 historical date. I am indebted to Mr. Hartung for the annexed drawing 
 of a lava at Port Moniz, which I did not visit myself. It is traversed by 
 
 Fig. 656. 
 
 Surface of lava near Port Moniz, N. W. point of Madeira; from a drawing by M. Hartung. 
 a. Channel traversing the lava. 
 
 a channel, a, like one of those already described, p. 503. 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 
 Auvcrgne 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 modem origin. 
 
CH. XXX. 1 TESTS OF AGE OF VOLCANIC ROCKS. 519 
 
 CHAPTER XXX. 
 
 ON THE DIFFERENT AGES OF THE VOLCANIC ROCKS. 
 
 Tests of relative ages 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 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 geo- 
 logical 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, superposition and intrusion, 
 with or without alteration of the rocks in contact ; 2d, organic remains ; 
 3d, mineral characters ; 4th, included fragments of older rocks. 
 
 Tests by superposition, &c. If a volcanic rock rests upon an aqueous 
 deposit, the former must be the newest of the twc ; 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. Superposition, therefore, is not of the same 
 
 Fig. 657. 
 E D 
 
 jull 
 
 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 per- 
 haps 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 belong- 
 ing 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 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 denuded, or because. 
 
520 
 
 TESTS OF RELATIVE AGE 
 
 [On. XXX. 
 
 Fig. 658. 
 
 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, Z>, c, and that after its consolida- 
 tion, the strata c?, 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 com- 
 plete, although the trap is in fact con- 
 temporaneous. We must not, therefore, hastily infer that the rock F is 
 intrusive, unless we find the strata c?, 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 correspond- 
 
 Fig. 659. 
 Magnesian limestone. 
 
 Coal. Dike. Coal. 
 
 Section at Quarrington Hill, east of Durham. (Sedgwick.) 
 a. Magnesian Limestone (Permian). 6. Lower New Red Sandstone, 
 
 c. Coal strata. 
 
 ing beds on the south side (see section, fig. 659). But the horizontal 
 beds of overlying Red Sandstone and Magnesian Limestone are not cut 
 through by the dike. Now here the coal-measures were not only depos- 
 ited, 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 denuda- 
 tion before the lower New Red Sandstone and Magnesian Limestone 
 were superimposed. Even in this case, however, although the date 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 Carbo- 
 niferous 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 gradually changing from the type 
 of the Carboniferous era to that of the Permian. 
 
Cn. XXX.] OF VOLCANIC ROCKS. 521 
 
 The test of age by superposition is strictly applicable to all stratified 
 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, scoriae, pumice, fine sand, and fragments of rock are 
 thrown up into the air, and then showered down upon the land, or into 
 neighboring lakes or seas. In the 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 imbedded, and thus continue as permanent 
 memorials of the geological period when the volcanic eruption occurred. 
 Tufaceous strata thus formed in the neighborhood of Vesuvius, Etna, Strom- 
 boli, 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 different 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 quad- 
 rupeds. 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 scoriaa 
 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 direction. 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 Ja- 
 maica, about 700 miles distant to the northeast. In the sea, also, at the 
 distance of 1100 miles from the point of eruption, Captain Eden of the 
 Conway sailed 40 miles through floating pumice, among which were some 
 pieces of considerable size.* 
 
 Test of age by mineral composition. As sediment of homogeneous 
 composition, when discharged from the mouth of a large river, is often 
 deposited simultaneously over a wide space, so a particular kind of lava, 
 flowing from a crater during one eruption, may spread over an extensive 
 area; as in Iceland in 1783, when the melted matter, pouriug from 
 Skaptar Jokul, flowed in streams in opposite directions, and caused a 
 continuous mass, the extreme points of which were 90 miles distant from 
 each other. This enormous current of lava varied in thickness from 100 
 feet to 600 feet, and in breadth from that of a narrow river gorge to 15 
 miles.f Now, if such a mass should afterwards be divided into separate 
 
 * Caldcleugh, Phil. Trans. 1836, p. 27. 
 f See Principles, Index, "Skaptar Jokul." 
 
522 RELATIVE AGES OF VOLCANIC ROCKS. [On. XXX. 
 
 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 
 prevailing character in lava emitted during the same eruption, and even 
 in the successive cirfrents 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 composition and 
 texture. 
 
 In Auvergne, the Eifel, and other countries where trachyte and basalt 
 are both present, the trachytic rocks are for the most part older than the 
 basaltic. These rocks do, indeed, sometimes alternate partially, as in the 
 volcano of Mont Dor, in Auvergne ; and we have seen that in Madeira 
 trachytic rocks may overlie an older basaltic series (p. 517) ; 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 upwards to the surface 
 by the expansive power of gases. Those materials, therefore, which 
 occupied 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 rela- 
 tive 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, in cases such 
 as those before alluded to, where the evidence of superposition 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 neighborhood of massive 
 trap. If the pebbles agree generally in mineral character with the 
 latter, we are then enabled to determine its relative age by knowing 
 that of the fossiliferous strata associated with the conglomerate. The 
 
CH. XXX.] POST-PLIOCENE VOLCANIC ROCKS. 523 
 
 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 j 
 another, and a far more considerable part, originated at times immedi- 
 ately antecedent, when the waters of the Mediterranean were already 
 inhabited by the existing species of testacea. The southern and eastern 
 flanks of Etna are skirted by a fringe of alternating sedimentary 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 impossible to distinguish any 
 one from species now living in the neighbouring 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 regarded 
 
 Fig. 660. 
 
 View of the Isle of Cyclops, in the Bay of Trezza.* 
 
 as the extremity of a promontory severed from the main land. Here 
 numerous proofs are seen of submarine eruptions, by which the argilla- 
 ceous and sandy strata were invaded and cut through, and tufaceous 
 breccias formed. Inclosed in these breccias are many angular and har- 
 dened fragments of laminated clay in different states of alteration 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 
 laminae of which are occasionally subdivided by thin arenaceous layers. 
 
 * This yiew of the Isle of Cyclops is from an original drawing by my friend 
 the late Capt. Basil Hall, R. N. 
 
524 
 
 VOLCANIC KOCKS OF 
 
 [Cn. XXX. 
 
 These strata dip to the K. 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-eastward 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 indurat- 
 ing process. 
 
 In the annexed woodcut (fig. 661) I have represented a portion of 
 the altered rock, a few feet square, where the alternating thin laminge 
 n ^ 6C1 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 partgj and 
 lays open its internal structure. 
 In the section thus exhibited, a 
 dike of lava is seen, first cutting 
 through an older mass of lava, 
 and then penetrating the super- 
 incumbent tertiary strata. In 
 one place the lava ramifies and 
 terminates in thin veins, from a 
 few feet to a few inches in 
 thickness. (See fig. 662.) 
 
 The arenaceous laminae are 
 much hardened at the point of 
 contact, and the clays are con- 
 verted into siliceous schist. In 
 this island the altered rocks as- 
 
 Contortions of strata in the largest of the Cyclopian SUme a honeycombed structure 
 
 on their weathered surface, sin- 
 gularly contrasted 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 with 
 carbonate of lime, and with a zeolite resembling analcime, which has 
 been called cyclopite. The latter mineral has also been found in small 
 fissures traversing the altered marl, showing that the same cause which 
 introduced the minerals into the cavities of the lava, whether we sup- 
 pose 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 "Prin- 
 ciples of Geology" the history of the changes which the volcanic region 
 
CH. XXX. 1 
 
 THE POST-PLIOCENE PERIOD. 
 Fig. 662. 
 
 525 
 
 Clay. Lara. 
 6. a. 
 
 Clay. 
 
 Lava. 
 
 Altered. 
 
 c. 
 
 Post-Pliocene strata inyaded by laya, Isle of Cyclops (horizontal section). 
 a. Lava. 6. Laminated clay and sand. c. The same altered. 
 
 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 formation of the modern 
 cone of Vesuvius since the year 79, and the production of several minor 
 cones in Ischia, together with that of Monte Nuovo in the year 1538. 
 Lava-currents have also flowed upon the land and along the bottom of 
 the sea volcanic sand, pumice, and scoriae have been showered down 
 so abundantly, that whole cities were buried tracts of the sea have 
 been filled up or converted into shoals and 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 Baiee, recent tufa- 
 ceous 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 height. These 
 post-pliocene strata, containing recent marine shells, alternate with dis- 
 tinct currents and sheets of lava which were of contemporaneous origin ; 
 and we find that in Vesuvius itself, the ancient co&e called Somma is of 
 far greater volume than the modern cone, and is intersected by a far 
 greater number of dikes. In contrasting this ancient part of the moun- 
 tain with that of modern date, one principal point of difference is ob- 
 served ; namely, the greater frequency in the older cone of fragments 
 
526 VOLCANIC EOCKS OF [Ca X3X. 
 
 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 angu- 
 lar 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 pro- 
 bability, 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 nume- 
 rous. 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 de- 
 structible than the intersected tuffs and porous lavas. In vertical extent 
 they vary from a few yards to 500 feet, and in breadth from 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 leucite 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 these 
 rents is an exception to the general rule ; for nothing is more remarka- 
 ble than the usual parallelism of the opposite sides of the dikes, which 
 correspond almost as regularly as the two opposite faces of a wall of 
 masonry. This character appears at first the more inexplicable, when 
 we consider how jagged and uneven are the rents caused by earthquakes 
 in masses of heterogeneous composition, like those composing the cone 
 of Somma. In explanation of this phenomenon, M. Necker refers us 
 to Sir W. Hamilton's account of an eruption of Vesuvius in the year 
 
 *. L. A. decker, Mem. de la Soc. de Phys. et d'Hist. Nat. de G6nve, torn. ii. 
 part i. Nov. 1822. 
 
CH. XXX.' 
 
 THE POST-PLIOCENE PERIOD. 
 
 Fig. 663. 
 
 527 
 
 Dikes or reins at the Punto del Naaone on Somma. (Necker.*) 
 
 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, continued their course in those channels, which were sometimes 
 full to the brim, and at other times more or less so, according to the 
 quantity of matter in motion. 
 
 u 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 chan- 
 nel. 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 vio- 
 lence 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 ero- 
 sion as the sides of the channels before adverted to. The prolonged and 
 uniform friction of the heavy fluid, as it is forced and made to flow up- 
 wards, 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 incandescent 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 ciystalline state ; 
 while at the edge the lava is somewhat vitreous, and always finer grained. 
 A thin parting band, approaching in its character to pitchstone, occasion- 
 
 * From a drawing of M. Necker, in Mem. above cited, 
 f PhiL Trans, vol. Ixx. 1780. 
 
528 POST-PLIOCENE VOLCANIC EOCKS. [On. XXX. 
 
 ally intervenes, on 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, 1 saw three 
 or four others in different parts of the great escarpment. These phenom- 
 ena are in perfect harmony with the results of the experiments of Sir 
 James Hall and Mr. Gregory Watt, which have shown that a glassy tex- 
 ture 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 flow- 
 ing in the open air. In this case the uppermost part, where it has been 
 in contact with the atmosphere, and where refrigeration 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 constituent 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 exhibited 
 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 obser- 
 vations of Mr. Dana; and in this case the refrigeration at the sides 
 would be more rapid than when the 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 pres- 
 sure 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 formation of 
 vertical columns in horizontal beds of lava ; for in both cases the divi- 
 
CH. XXX.] NEWER PLIOCENE VOLCANIC ROCKS. 
 
 529 
 
 sions 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. 156) 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 intersecting 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 occasionally 
 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 j in others, though rarely, columnar. I found dikes 
 of amygdaloid, wacke, and prismatic basalt, intersecting the limestone 
 at the bottom of the hollow called Gozzo degli Martiri, below Melilli. 
 
 Dikes. Dikes of vesicular and amygdaloidal lava are also seen tra- 
 versing marine tuff or peperino, west of Palagonia, some of the pores 
 of the lava being empty, while others are filled with carbonate of lime 
 
 Fig. 664. 
 
 Ground-plan of dikes near Palagonia. 
 a. Lara. 
 
 6. Peperino, consisting of rolcanic sand, mixed with 
 fragments of lava and limestone. 
 
 In such cases, we may suppose the peperino to have resulted from 
 showers of volcanic sand and scoriae, together with fragments of lime- 
 stone, thrown out by a submarine explosion, similar to that which gave 
 rise to Graham Island in 1831. When the mass was, to a certain 
 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 
 
 34 
 
530 PLIOCENE VOLCANOS. [On. XXXI. 
 
 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 superincum- 
 bent 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 communication by which the subterranean 
 lavas reached the surface. 
 
 CHAPTER XXXI. 
 
 ON THE DIFFERENT AGES OF THE VOLCANIC ROCKS continued. 
 
 Volcanic rocks of the Older Pliocene period Tuscany Home Volcanic region 
 of Olot in Catalonia Cones and lava-currents Eavines and ancient gravel- 
 beds Jets of air called Bufadors Age of the Catalonian volcanos Miocene 
 period Brown coal of the Eifel and contemporaneous trachytic breccias 
 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, submarine 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 Sub- 
 apennine 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 favor 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^ 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 differ- 
 ence 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 
 
 * See 1st edit, of Principles of Geology, vol. iii. chaps, xiii. and xiv. 1833; and 
 former edits, of this work, ch. XXXL 
 f Geol. Quart. Journ. vol. vi. p. 281. 
 j Catalogue des Fossiles de Monte Mario, Rome, 1854. 
 
Or. XXXI.] 
 
 VOLCANOS OF CATALONIA. 
 
 531 
 
 neighborhood 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 volcanio groups scattered over Europe a precise geological 
 place in the tertiary series ; but I shall describe here, as probably refer- 
 able 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 Cata- 
 lonia 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. MacClure, 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 Pyre- 
 nees, for traces of a lava-current; and I can say, with confidence, that 
 
 * Maclure, Journ. de Phys., vol. Ixvi. p. 213, 1808; cited by Daubeny, De 
 scription of Volcanos, p. 24. 
 
532 VOLCANOS OF CATALONIA.' [On. XXXI. 
 
 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 gray and greenish 
 sandstone and conglomerate, with some thick beds of nurnmulitic lime- 
 stone. The conglomerate contains pebbles of quartz, limestone, and 
 Lydian stone. This system of rocks is very extensively spread throughout 
 Catalonia ; one of its members being a red sandstone, to whih the cele- 
 brated 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 'Janks, causing 
 them to dip to the north and northwest. This dip, which is towards 
 the Pyrenees, is connected with a distinct axis of elevatioa, and pre- 
 vails 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 under- 
 gone 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 intersected by ravines, or exhibit marks of ero- 
 sion by running water. 
 
 Fig. 667. 
 
 View of the Volcanos around Olot in Catalonia. 
 
CH. XXXI.] PLIOCENE YOLCAXOS. 533 
 
 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 neighborhood of Clot, some of which 
 (fig. 667, Nos. 2, 3, and 5) are represented in the above drawing ; 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 sur- 
 rounding country. 
 
 In the above 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 hy- 
 pogene and ancient fossiliferous rocks. In front of these are the fossilifer- 
 ous formations (No. 4) which are in shade. Still nearer to us, the hills 
 2, 3, 5 are volcanic cones, and the rest o%the ground on which the sun- 
 shine 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 mentioned. The 
 bed of the river is hard basalt ; and at the bridge qf Santa Madalena are 
 seen two distinct lava-currents, one above the other, separated by a hori- 
 zontal 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 frag- 
 ments 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 volcanoes are as entire as those in the neigh- 
 borhood 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 cir- 
 cular depression or crater at the summit It is chiefly made up of 
 red scoriae, undistinguishable from those of minor cones of Etna. The 
 neighboring hills of Olivet (No. 2) and Garrinada (No. 5) are of simi- 
 lar 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 sand 
 stone, shale, and limestone, as have those of the Eifel, in Germany, to 
 DA described in the sequel, there is a remarkable difference in the nature 
 
 * This view is taken from a sketch which I made on the spot in 1839. 
 
534: PLIOCENE YOLCANOS. * [Cn. XXXI. 
 
 of the ejections composing the cones in these two regions. In the Eifel, 
 the quantity of pieces of sandstone and shale 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 Olot for a single fragment 
 of any extraneous rock ; and Don Francisco Bolos, an eminet botanist 
 of Olot, informed me that he had never been able to detect any. Vol- 
 Fig 668 canic sand and ashes are not confined 
 
 to the cones, but have been some- 
 times scattered by the wind over the 
 country, and drifted into narrow val- 
 leys, as is seen between Olot and 
 Cellent, where the annexed section 
 (fig. 668) is exposed. The light 
 
 a. Secondary conglomerate. cindery volcanic matter rests in thin 
 
 p. Thin seams of volcanic sand and scoriae. . * _ 
 
 regular layers, just as it alighted on 
 
 the slope formed by the solid conglomerate. No flood could have passed 
 through the valley since the storiae fell, or these would have been for 
 the most part removed. 
 
 The currents of lava in Catalonia, like those of Auvergne, the Viva- 
 rais, Iceland, and all mountainous countries, are of considerable 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 declivity 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 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 porous, and assumes a sphe- 
 roidal 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 five 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 vol- 
 canic eruptions, and which, unless protected, as here, by superincumbent 
 lava, is washed away from the surface of the laud. 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 underlying limestone. 
 Occasionally an alluvium, several feet thick, is interposed between the 
 
CH. XXXL] 
 
 YOLCANOS OF CATALOXIA. 
 
 535 
 
 Fig. 669. 
 
 Section above the bridge of Cellent 
 
 a. Scoriaceous lava. 
 
 b. Schistose basalt. 
 
 c. Columnar basalt. 
 
 fl. Scoriae, vegetable soil, and alluvium. 
 . Nummulitic limestone. 
 j. Micaceous grey sandstone. 
 
 gneous 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 ob- 
 served in this part of Spain, is seen in the bottom of a valley near 
 San Feliu de Pallerdls, 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 probably 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. 
 
 Fig. era 
 
 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. 
 c. Inclined strata of secondary sandstone. 
 
530 PLIOCENE VOLCANOS. [On. XXXI. 
 
 I shall describe one more section to elucidate the phenomena 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 180 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. 474)' has been 
 left, which was probably never so high as the cliff A, as it may have con- 
 stituted 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 down- 
 wards into a spheroidal basalt ; some of the huge spheroids being no less 
 than 6 feet in diameter. Below this is a more compact basalt, with crys- 
 tals of olivine. There are in all five distinct ranges of basalt, the upper- 
 most 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 dif- 
 ferent 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 num- 
 ber, called in the country "bufadors," from which a current of cold 
 air issues during summer, but which in winter 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 unusually 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 destroyed by an earthquake, 
 an eruption broke out near Amer, and consumed the town. The re- 
 searches 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 j and any 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 
 
CH. XXXI.] MIOCENE VOLCANIC ROCKS. 537 
 
 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 cav- 
 ernous nature of the subjacent rocks ; for Catalonia is beyond the line of 
 those European earthquakes which have, within the period of history, de- 
 stroyed 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 synoptical form, the re- 
 sults obtained from numerous sections. 
 
 The more modern alluvium (d) is partial, and has been formed by 
 
 Fig. 671. 
 
 Superposition of rocks in the vokanic district of Catalonia. 
 
 a. Sandstone and nummulitic limestone. 
 
 b. Older alluvium without volcanic pebbles. 
 
 c. Cones of scoriae and lava. d. Newer alluvium. 
 
 the action of rivers and floods upon the lava ; whereas the older gravel 
 (>) was strewed over the country before the volcanic eruptions. In 
 neither have any organic remains been discovered ; so that we can merely 
 affirm, as yet, that the volcacos broke out after the elevation of some 
 of the newest rocks of the nummulitic (Eocene) series of Catalonia, and 
 before the formation of an alluvium (d) of unknown date. The integrity 
 of the cones merely shows that the country has not been agitated by vio- 
 lent 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 vol- 
 canic rocks of the lower Rhine and the Eifel are also involved in a con- 
 siderable degree of ambiguity ; but we know that some portion of them 
 were coeval with certain tertiary deposits called " Brown-Coal" by the 
 
538 
 
 MIOCENE VOLCANIC KOCKS. 
 
 [Cn. XXXI. 
 
 Germans, which probably belong in part to the Miocene, and in part to 
 the Upper Eocene,- epoch. 
 
 This JBrown-Coal is seen on both sides of the Rhine, in the neighbor- 
 hood of Bonn, resting unconforraably 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.* 
 
 The Brown-coal formation of that region consists of beds of loose sand, 
 sandstone, and conglomerate, clay with nodules of clay-ironstone, and oc- 
 casionally silex. Layers of light brown, and sometimes black lignite, are 
 interstratified with the clays and sands, and often irregularly diffused 
 
 Fig. 672. 
 
 Map of the volcanic region of the Upper and Lower Eifel. 
 1234 5 English miles. 
 
 (.-:..-..-. . | Volcanic J A. of the Upper Eifel. < .-^ \ Points of eruption, with craters and 
 
 L/Sr^Sj District ( B. of the Lower Eifel. \ ^^ I scoriae. 
 
 Trachyte. 
 
 Basalt. 
 Brown coal. 
 
 ZV. B. The country in that part of the map which is left blank is composed of inclined Silurian 
 and Devonian rocks. 
 
 * Horner, Trans, of Geol. Soc. 2d ser. vcL v. 
 
CH. XXXL] AGE OF THE BROWN COAL. 539 
 
 through them. They contain numerous impressions of leaves and stems 
 of trees, and are extensively worked for fuel, whence the name of the 
 formation. 
 
 In 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 Flabellaria. 
 Ceanothus, and Daphnogene, including D. cinnamomifolia (fig. 169, 
 p. 191), occur in these beds, with nearly 150 other plants, if we include 
 all which have been named from the somewhat uncertain 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 inver- 
 tebrate, many are peculiar, while some few, such as Littorinella acuta, 
 Desh., help to approximate these strata with some of the upper fresh- 
 water 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. 1 90, to the Limburg group, called Upper Eocene 
 in this work. But in regard to the Rhenish freshwater deposits near 
 Bonn, so large a proportion 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 p. 104. 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 eventually made 
 out from the tertiaries of the north of Germany, on which the labors 
 of M. Beyrich have thrown so much light, to the faluns of the Loire, 
 by the discovery of beds intermediate in age and paleoutological char- 
 acters, the best line of demarcation that we can adopt is that pro- 
 posed 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. 192), 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 Siebengebirges am Rhein. Bonn. 1852. 
 
 j- "While this sheet was passing through the press, a valuable paper on the 
 Brown-Coal and other deposits of the Mayence Basin, by "William J. Hamilton, 
 Esq., P. G. S., has been published (Geol. Quart. Journ., vol. x. p. 254), in which 
 the question of classification above alluded to is discussed. Whatever termi- 
 
540 TEKTIAKY VOLCANIC ROCKS. [On. XXXI. 
 
 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 vry distinct in char- 
 acter 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 5 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 
 interstratified 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. 123), that this intercalation of volcanic matter between 
 beds of loess may possibly be explained without supposing the last erup- 
 tions 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, resem- 
 bling 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 hap- 
 pened 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 pre- 
 viously observed by me in those of France, Italy, or Spain, I shall briefly 
 describe them. The fundamental rocks of the district are gray and red 
 
 nology be adopted, I would strongly urge the necessity of referring the Hemp- 
 stead beds of the Isle of Wight and the Limburg strata to one and the same 
 period, whether it be named Lower Miocene or Upper Eocene. 
 
CH, XXXI.] 
 
 TERTIARY VOLCANIC ROCKS. 
 
 sandstones and shales, with some associated limestones, replete with fossils 
 of the Devonian or Old Red Sandstone 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, and frequently on intervening platforms. In travelling through 
 this district we often fall upon them most unexpectedly, and 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 ecge 
 of a tarn, or deep circular lake-basin (see fig. 673). 
 
 rig. eia 
 
 The Gemunder Maar. 
 
 Fig. 674. 
 
 a. Village of Gemund 
 Z>. Gemunder Maar. 
 
 c. Weinfeldcr Maar. 
 
 d. Schalkenmchren 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 
 neighboring cavities. On viewing the first of these (fig. 673), we recog- 
 nize 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 
 
542 LAKE CKATERS OF THE EIFEL. [Ca XXXI. 
 
 shale which exhibit no signs of the action of heat ; and we look in vain 
 for those beds of lava and scorise, 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 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 sur- 
 rounded 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 forty-five degrees ; on the exterior, of thirty-five 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, hol- 
 lowed 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 scoriaB 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 neighborhood is a mountain called the Mosenberg, 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 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. 6*75), which I can only explain by supposing that fragments of red-hot 
 
 Stratified rocks. . Yolcanic. 
 
 Outline of the Mosenberg, Upper Eifel. 
 
 * Scrope, Edin. Journ. of Science, June, 1826, p. 145. 
 \ Hibbert, Extinct Volcanos of the Rhine, p. 24. 
 

 CH. XXXI.] MIOCENE VOLCANIC ROCKS. 543 
 
 lava, as they fell round the vent, were cemented together into one com- 
 pact mass, in consequence of continuing to be in a half-melted state. 
 
 If we pass from the upper to the lower Eifel, from A to B (see map, p. 
 538), we find the celebrated lake-crater of Laach, which has a greater re- 
 semblance than any of those before mentioned to the Lago di Bolsena, 
 and others in Italy being surrounded by a ridge 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 scoriae and tufaceous sand. 
 The opposite wall of the crater is composed of cinders and scorified 
 rock, like that at the summit of Vesuvius. 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 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 sand- 
 stone 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 scoria, has escaped from the newly-formed cavity. 
 There is, indeed, no feature in the Eifel volcanos more worthy of note, 
 than the proofs they afford of very copious aeriform discharges, unac- 
 companied by the pouring ont 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 
 'if ted 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 nume- 
 
544 HUNGAKY. [Cn. XXXI. 
 
 rous trunks and branches of trees. If this trass was formed during the 
 period of volcanic eruptions it may perhaps have originated in the man- 
 ner of the moya of the Andes. 
 
 We may easily conceive that a similar mass might now be produced, 
 if a copious evolution of gases should occur in one of the lake basins. 
 The water might remain for weeks in a state of violent 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 occur- 
 rence of the numerous trunks of trees dispersed irregularly through the 
 trass, can be explained. 
 
 Hungary. M. Beudant, in his elaborate work on Hungary, describes 
 five distinct groups of volcanic rocks, which, although nowhere of great 
 extent, form striking features in the physical geography 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 Santo- 
 rin and Milo now do in the Grecian Archipelago ; and M. Beudant has 
 remarked that the mineral products of the last-mentioned islands resem- 
 ble remarkably those of the Hungarian extinct volcanos, where many 
 of the same minerals, as opal, chalcedony, resinous silex (silex resinite), 
 pearlite, obsidian, and pitchstone abound. 
 
 The Hungarian lavas are chiefly felspatjiic, 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 conglom- 
 erates, 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 Lancerote, 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 b'uried in tuffs on the flanks 
 of the mountains, are supposed to have become siJicificd. 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 imbedded 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. 
 
CH. XXXH] TERTIARY VOLCANIC ROCKS. 545 
 
 CHAPTER XXXE. 
 
 ON THE DIFFERENT AGES OF THE VOLCANIC ROCKS Continued. 
 
 Volcanic rocks of the Pliocene, Miocene, and Eocene periods continued Au- 
 vergne Mont Dor Breccias nnd 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 C6me 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 Xew 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 eruptions 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. 196). 
 
 The earliest monuments of the tertiary period in that region are 
 lacustrine deposits of great thickness (2, fig. 676, p. 547), 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. 607) containing upper Eocene 
 shells and bones of mammalia, the higher beds of which sometimes al- 
 ternate with volcanic tuff of contemporaneous origin. After the filling 
 up or drainage of the ancient lakes, huge piles of trachytic and basaltic 
 rocks, with volcanic breccias, accumulated to a thickness of several thou- 
 sand feet, and were superimposed upon granite, or the contiguous lacus- 
 trine strata. The greater portion of these igneous rocks appear to have 
 originated during the Miocene and Pliocene periods ; and extinct quad- 
 rupeds 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 fresh-water strata.* This great mountain rises suddenly 
 
 to the height of several thousand feet above the surrounding platform, 
 
 and retains the shape of a flattened and somewhat 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 scoria?, 
 
 pumice stones, and their fine detritus, with interposed beds of trachyte 
 
 * See the map, p. 195. 
 
 35 
 
546 MONT DOE, AUVEKGNE. [Ca XXXII. 
 
 and basalt, which descend often in uninterrupted sheets, until they reach 
 and spread themselves round the base of the mountain.* Conglome* 
 rates also, composed of angular and rounded fragments of igneous rocks, 
 are observed to alternate with the above ; and the various masses are 
 seen to dip off from the central axis, and to lie parallel to the sloping 
 flanks of the mountain. 
 
 The summit of Mont Dor terminates in seven or eight rocky peaks, 
 where no regular crater can now be traced, but where we may easily 
 imagine one to have existed, which may have been shattered by earth- 
 quakes, and have suffered degradation by aqueous agents. Originally, 
 perhaps, like the highest crater of Etna, it may have formed an insig- 
 nificant 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 scoriae. I have 
 explained my reasons for objecting to this view in Chapter 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. 490), 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 supposing that the 
 basaltic currents of the ancient French volcano were at first more hori- 
 zontal 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 disten- 
 sion of the mass, beds of lava and scoriae may, in some places, have 
 acquired a greater, in others a less inclination, 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 ear- 
 liest eruptions were posterior in origin to those grits, and conglomerates 
 of the fresh-water formation of the Limagne, which contain no pebbles 
 of volcanic rocks ; while, on the other hand, some eruptions took place 
 before the great lakes were drained; and others occurred after the 
 desiccation of those lakes, and when deep valleys had aleady been exca- 
 vated through fresh-water strata. 
 
 In the annexed section, I have endeavored to explain the geological 
 structure of a portion of Auvergne, which I re-examined in 1843.J It 
 * Scrope's Central France, p. 98. 
 
 f See chaps, xxiv. xxv. and xxvi. 7th, 8th, and 9th editions, 
 j See Quarterly Geol. Journ. voL ii. p. 77. 
 
CH. XXXII] TERTIARY VOLCANIC ROCKS. 54Y 
 
 
 Fig. 6T6. 
 
 
 
 Mont Perrier. 
 
 
 
 * Sc s * 
 
 nfljf of the Toor . 
 
 5 
 
 /"nTiTgrrrn '.^aimM^fc- > * 
 
 Allier. Boula.1 
 
 3\ 
 
 c BzeR - vi^^MB^ 
 
 t "-* .,/? 
 
 w& 
 
 ^ ^^^x^^^:^^->^^^^ 
 
 
 Section from the valley of the Couze at Nechers, through Mont Perrier and Issoire to the Vallej 
 of the Allier, and the Tour de Boulade, Auvergne. 
 
 10. Lara-current of Tartaret near its termina- 5. Lower bone-bed of Perrier, ochreous sand 
 tion at Nechers. and gravel. 
 
 9. Bone-bed, red sandy clay under the lava of 4 a. Basaltic dyke. 
 
 Tartaret. 4. Basaltic platform. 
 
 8. Bone-bed of the Tour de Boulade. 3. Upper fresh-water beds, limestone, marl, 
 
 7. Alluvium newer than No. 6. gypsum, Ac. 
 
 6. Alluvium with bones of hippopotamus. 2. Lower fresh-water formation, red clay, green 
 
 5 c. Trachytic breccia resembling 5 a. sand, Ac. 
 
 5 b. Upper bone-bed of Perrier, gravel, Ac. 1. Granite. 
 
 5 a. Pumiceous breccia and conglomerate, angu- 
 lar masses of trachyte, quartz, pebbles, Ac. 
 
 may convey some idea to the reader of the long and . om plicated 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 fresh-water 
 beds (No. 3j, once formed in a lake, must have suffered great destruc- 
 tion before the excavation of the valleys of the Couze and Allier had 
 begun. In these fresh-water 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 fresh- 
 water beds, and may have been of Upper Eocene or Miocene date, giv- 
 ing 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 fresh-water 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 are 
 supposed, from their similarity to others found on Mount Dor, to have 
 descended from the flanks of that mountain during eruptions ; and the 
 interstratified alluvial deposits contain the remains of mastodon, rhino- 
 ceros, 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, 
 
548 VOLCANOS OF AUYEKGNE. [Ca XXXII 
 
 whether they may not ratheft be ascribed to the older Pliocene epoch is 
 a question which farther inquiries and comparisons must determine. 
 
 Whatever be their date in the tertiaiy series, they are quadrupeds 
 which inhabited the country when the formations 5 and 5 c originated. 
 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 suddenly melted by lava, causing 
 a deluge of water to bear down fragments 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 an- 
 cient inundations swept, was first excavated at the expense of the for- 
 mations 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 by M. 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 freshwater 
 limestone (No. 8) was formed, called the bone-bed of the Tour de Bou- 
 lade, from which a great many other mammalia have been collected by 
 MM. Bravard and Pomel. In this assemblage the Eleplias primigenius 
 Rhinoceros tichorinus, Deer (including rein-deer), Eqims, Bos, Antelope, 
 FeliSj 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. 6*76) 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 eruptipn 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 hap- 
 pened ; for it was evidently thrown up at the bottom of the existing 
 valley, which is bounded by lofty precipices composed of sheets of an- 
 cient columnar trachyte and basalt, which once flowed at very high levels 
 from Mont Dor.* 
 
 * For a view of Puy de Tartaret and Mont Dor, see Scrope's Volcanos of Cen- 
 tral France. 
 
CH. XXXIL] TEKTIARY VOLCANIC ROCES. 549 
 
 When we follow the course of the river Couze, from its source m the 
 lake of Chambon, to the termination of the lava-current at Nechers, a dis- 
 tance 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 Tar- 
 taret, 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), we 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 extinct 
 horse, Equmfossilis. The other species, obtained from the same bed, 
 are referable to the genera Sus, Bos, Ccrvus f Felis, Canis, Maries, Talpa, 
 SoreXj LepuSj Sciurm, Mus, and Logomys, 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 liortensis, H. nemoralis, H. la- 
 pitida, 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 geological date to that event, which must, in that 
 case, have belonged to the Newer-Pliocene, or, perhaps, the Post-Plio- 
 cene period. That the current, which has issued from the Puy de Tar- 
 taret, 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 pre- 
 cisely 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 
 
550 VOLCANOS OF AUVERGNE. [On. XXXII. 
 
 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 granitic platform, form an irregular 
 ridge (see fig. 621, p. 462), about 18 miles in length, and 2 in breadth. 
 They are usually truncated at the summit, where the crater is often pre- 
 served entire, the lava having issued from the base of the hill. But fre- 
 quently the crater is broken down on one side, where the lava has flowed 
 out, The hills are composed of loose scoriae, blocks of lava, lapilli, and 
 pozzuolana, with fragments of trachyte and granite. 
 
 Puy de Cdme. 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 presents 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 dis- 
 tance 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. Mean- 
 while the cone of Come remains unimpaired, its loose materials being 
 protected by a dense vegetation, and the hill standing on a ridge not com- 
 manded 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 station- 
 ary condition. In this place, therefore, we behold in the results of aque- 
 ous 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 
 Eouge, a conical hill to the north of the village of Pranal. The cone is 
 composed entirely of red and black scoriae, tuff, and volcanic 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, 
 
 * Scrope's Central France, p. 60, and plate. 
 
CH. XXXIL] 
 
 TERTIARY VOLCANIC ROCKS. 
 
 551 
 
 we see a great mass of black and red scoriaceous lava becoming more 
 and more columnar towards its base. (See fig. 677). Below this is a bed 
 
 Fig. 677. 
 
 a. Scoriaceons lava. 
 6. Columnar basalt 
 c. Gravel 
 
 D. Ancient mining gallery. 
 
 E. Pathway. 
 / Gneiss. 
 
 Lava-current of Chaluzet, Auvergne, near its termination.* 
 
 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 continuous, in a horizontal direction, between the gneiss and 
 the volcanic mass. Here again it is quite evident, that, while the basalt 
 was gradually 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 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. JSTo rills can collect where all the rain is in- 
 stantly absorbed by the sand and scoria?, as is remarkably the case on 
 Etna ; and nothing but a waterspout breaking directly upon the Puy de 
 Pariou could carry away a portion of the hill, so long as it is not rent or 
 engulfed by earthquakes. 
 
 * Lyell and Murchison, Ed. New PhiL Journ. 1829. 
 
552 TERTIAEY VOLCANIC ROCKS. [Cn. XXXII. 
 
 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 en- 
 camped upon the plains of Auvergne, and laid siege to its principal city 
 (Gergovia, near Ciermont), could hardly have failed to notice them. 
 Had there been any record of their eruptions in the time of Pliny or Si- 
 donius 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.* 
 
 Vclay. The observations of M. Bertrand de Doue have not yet es- 
 tablished 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 channel 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 volcanic rocks has been ob- 
 served. 
 
 At St. Privat d'Allier a bed of volcanic scoriae and tuff was discovered 
 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 Rhino- 
 ceros leptorliinus, Hyaena speldea, and a species allied to the spotted 
 hyaena of the Cape, together with four undetermined species of deer. 
 The manner of the occurrence of these bones reminds us of the pub- 
 lished accounts of an eruption of Coseguina, 1835, in Central America 
 (see p. 521), during which hot cinders and scoriae fell and scorched to 
 death great numbers of wild and domestic animals and birds. 
 
 Plomb du Cantal. In regard to the age of the igneous rocks of the Can- 
 tal, we can at present merely affirm, that they overlie the (Upper ?) Eocene 
 lacustrine strata of that country (see Map, p. 195). They form a great 
 dome-shaped mass, having an average slope of only 4, which has evi- 
 dently 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, forming a mountain several thou- 
 sand feet in height. Dikes also of phonolite, trachyte, and basalt are 
 numerous, especially in the neighbourhood 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, occupies the middle of the cavity. f It is clear 
 that the volcano of the Cantal broke out precisely on the site of the 
 * Daubeny on Volcanos, p. 14. 
 f Mem. de la Soc. Geol. de France, torn. i. p. 176. 
 
CH. XXXIL] EOCENE VOLCANIC ROCKS. 553 
 
 lacustrine deposit before described (p. 204), 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 ob- 
 served, nor any tuffs containing fresh-water shells, although some of 
 these tuffs include fossil remains of terrestrial plants, said to imply seve- 
 ral distinct restorations of the vegetation of the mountain in the inter- 
 vals 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. 195), where fresh-water limestone and marl are seen covered by a 
 thickness of about 800 feet of volcanic rock. Shifts are here seen in 
 the strata of limestone and marl.* 
 
 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 deposition 
 of the fresh-water 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 neighboring ventf 
 
 Another example occurs in the Puy de Marmont, near Veyres, where 
 a fresh-water 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 subsiding 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 
 * See Lyell and Murchison, Ann. de Sci. Nat,, Oct. 1829. 
 f See Scrope's Central France, p. 21. 
 
554: 
 
 EOCENE VOLCANIC HOCKS. 
 
 [On. XXXII. 
 
 alternation here of a contemporaneous sheet of lava with freshwater 
 strata in the manner supposed by some other observers ;* but the posi- 
 tion and contents of some of the associated tuffs, prove them to have 
 been derived from volcanic eruptions which occurred during the deposi- 
 tion 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 Mer- 
 dogne. The dike here cuts through the marly strata at a considerable 
 angle, producing, in general, great alteration and confusion in them for 
 some distance from the point of contact. Above the white and green 
 
 Fig. 678. 
 
 White 
 and green 
 marls. 
 
 Hill of Gergovia. 
 
 marls, a series of beds of limestone and marl, containing fresh-water 
 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. Oc- 
 casionally 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, and a Melanop&t, but they were not suffi- 
 cient to enable me to determine 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 limestones, 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 chalcedony, and crystals of mesotype, stilbite, and arrago- 
 nite. To formations of this class may belong some of the breccias 
 immediately adjoining the dike in the hill of Gergovia; but it cannot be 
 contended that the volcanic sand and scoriae interstratified with the marls 
 
 * See Scrope's Central France, p. 7. 
 
CH. XXXII] CRETACEOUS VOLCANIC ROCKS. 555 
 
 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 deposi- 
 tion 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 alter- 
 nate conformably with cretaceous limestone and greensand between Kas- 
 tri 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 es- 
 tablished by the following proofs ; first, the lithographic limestones of 
 the Cretaceous era are cut through by trap, and then a conglomerate 
 occurs, at Nauplia and other places, containing in its calcareous cement 
 many well-known fossils of the chalk and greensand, together with peb- 
 bles 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 dur- 
 ing 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 coun- 
 try, originated contemporaneously with the Oolite which they traverse and 
 overlie, has been ascertained by Prof. E. Forbes, in 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.f 
 
 Trap of the New Red Sandstone penod. 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 subsequently 
 into the sandstone, but were produced by contemporaneous volcanic 
 action. Some beds of grit, mingled with ordinary red marl, resemble 
 sands ejected from a crater ; and in the stratified conglomerates occurring 
 near Tiverton are many angular fragments of trap porphyry, some of them 
 * Boblaye and Virlet, Morea, p. 23. 
 f GeoL Quart Journ. 1851, vol. vii. p. 108. 
 
556 
 
 VOLCANIC ROCKS OF THE 
 
 [On. XXXII. 
 
 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 Fife- 
 *hire, where they consist of basalt with olivine, amygdaloid, greenstone, 
 
 Fig. 6T9. 
 
 Eock and Spindle, St Andrew's, as seen in 1888. 
 a. Unstratified tuff. &. Columnar greenstone. c. Stratified tuffi 
 
 * De la Beche, Geol. Proceedings, No. 41, p. 198. 
 
CH. XXXIL] CARBONIFEROUS PERIOD. 557 
 
 wacke, and tuff. They appear to have been erupted while the sediment- 
 ary 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 Lo- 
 mond, 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 traps, one of which (fig. 679) is aptly called the 
 "rock and spindle,"* 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 termina- 
 tions of the 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 extremity 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 arrange themselves at right angles, 
 
 as before explained (p. 484). -wise at &, fig. 679. 
 
 A trap dike was pointed out to me by Dr. Fleming, in the parish 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 foi many miles, passing through the amygdaloidal and 
 other traps of the hill called Normans 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, per- 
 haps titaniferous, is also present. The result of this analysis is interest- 
 ing, because both the ancient and modern lavas of Etna consist in like 
 manner of augite, Labradorite, and titaniferous iron. 
 
 * " The rock," as English readers of Burns' poems may remember, is a Scotch 
 term for distaff. 
 
558 SILURIAN VOLCANIC ROCKS. [On. XXXII. 
 
 Trmp 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 conglom 
 erates are sometimes composed of granitic and quartzose rocks, some 
 times exclusively of different varieties of trap, which, although pur- 
 posely omitted in the section referred to, are often found either intruding 
 themselves in amorphous masses and dikes into the old fossiliferous tile- 
 stones, No. 4, or alternating with them in conformable beds. All the 
 different divisions of the red sandstone, 1, 2, 3, 4, are occasionally inter- 
 sected by dikes, but they are very rare in Nos. 1 and 2, the upper mem- 
 bers 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 sand- 
 stone period. 
 
 The trap rocks alluded to consist chiefly of felspathic porphyry and 
 amygdaloid, the kernels of the latter being sometimes calcareous, often 
 chalcedonic, 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 green- 
 stone, 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. Mur- 
 chison in Shropshire, that when the lower Silurian strata of that county 
 were accumulating, there were frequent volcanic eruptions beneath the 
 sea ; and the ashes and scoria then ejected gave rise to a peculiar kind 
 of tufaceous sandstone or grit, dissimilar to the other rocks of the Silu- 
 rian series, and only observable in places where syenitic and other trap 
 rocks protrude. These tuffs occur on the flanks of the Wrekin and 
 Caer Caradoc, and contain Silurian fossils, such as casts of encrinites, 
 trilobites, and 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 sedimentary strata of the 
 lower Silurian system. This trap consists of slaty porphyry and granu- 
 lar felspar rock, the beds being traversed by joints like those in the 
 associated sandstone, limestone, and shale, and having the same strike 
 and dip.f 
 
 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, clinkstone, and other va- 
 
 * Murchison, Silurian System, &c. p. 230. f Ibid. p. 272. 
 
On. XXX1U CAMBRIAN VOLCANIC ROCKS. 559 
 
 neties , and the interposed Llandeilo flags are of sandstone and shale, 
 with trilobites and graptolites.* 
 
 Cambrian Volcanic Rocks. In a former chapter (Ch. XXVIL p. 447), 
 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 tliickness, 
 which may be called Cambrian. The upper subdivision, named by Pro- 
 fessor 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. 448 ; 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, occurring 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 sup- 
 posed to have been produced contemporaneously with the stratified chlo- 
 ritic slates by submarine eruptions oftentimes repeated, the materials of the 
 slates having been supplied, in part at least, from the same source.f 
 
 * Murehison, Silurian System, dzc. p. 825. 
 f Geoi Trans. 2d series, voL iv. p. 55. 
 
560 PLUTONIC ROCKS. [On. XXXIII 
 
 CHAPTER XXXIII. 
 
 PLUTONIC ROCKS GRANITE. 
 
 General aspect of granite Decomposing into spherical masses Rude columnar 
 structure Analogy and difference of volcanic and plutonic formations Mine- 
 rals 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 com- 
 position 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 overlying 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 unstratified 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 erup- 
 tions 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 crystal- 
 lized 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, dis- 
 tinct ; 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 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 vegetatioa 
 
CH. XXXIII. ] 
 
 GENERAL ASPECT OF GRANITE. 
 
 561 
 
 The surface of the rock is for the most part in a crumbling state, and 
 he hills are often surmounted by piles of stones like the remains of a 
 stratified mass, as in the annexed figure, and sometimes like heaps of 
 boulders, for which they have been mistaken. The exterior of these 
 
 Fig. 681. 
 
 Mass of granite near the Sharp Tor, Cornwall. 
 
 Btones, 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 
 characteristic of basalt and other volcanic formations, and it must be 
 referred 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. Examples of these 
 appearances may be seen near the Land's End, in Cornwall. (See 
 figure 682.) 
 
 Fig. 6S2. 
 
 Granite having a cuboidal and rude columnar structure, Land's End, Cornwall. 
 
 The plutonic formations also agree with the volcanic, in having veins 
 >r ramifications proceeding from central masses into the adjoining rocks, 
 
 36 
 
562 MINERAL COMPOSITION OF GRANITE. [Cn. XXXIII 
 
 aiid 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 inde- 
 finite extent appearing to have originated 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 insensible 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. 590), except in the variety termed graphic granite, which 
 occurs mostly in granitic veins. This variety is a 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 
 
 Fig. 683. Jig. 684. 
 
 Graphic granite. 
 
 Fig. 683. Section parallel to the laminae. 
 Fig. 684. Section transverse to the laminae. 
 
 them the space now occupied by the darker-colored quartz. This min- 
 eral, when a section is made 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 ingenious specu- 
 lation. We should naturally have anticipated that, during the cooling 
 of the mass, the flinty portion would be the first to consolidate ; and 
 that the different varieties of felspar, as well as garnets and tourmalines, 
 being more easily liquefied by heat, would be the last. Precisely the 
 
G*n. XXXIII.] PORPHYRITIC GRANITE. 563 
 
 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 ex- 
 planations of this phenomenon have been proposed by MM. de Beau- 
 mont, Fournet, and Durocher. They refer to M. Gaudin's experiments 
 on the fusion of quartz, which show that silex, as it cools, has the prop- 
 erty of remaining in a viscous state, whereas alumina never does. This 
 " gelatinous flint" is supposed to retain a considerable degree of plas- 
 ticity long after the granitic mixture has acquired a low temperature ; 
 and M. E. de Beaumont suggests, that electric action may prolong the 
 duration of the viscosity of silex. Occasionally, however, we find the 
 quartz and felspar mutually imprinting their forms on each other, afford- 
 ing 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 color ; and 2dly, felspar in 
 smaller crystals, in which soda predominates, usually of a dead white or 
 spotted, and striated like albite, but not the same in composition.! 
 
 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 of the Land's 
 End, in Cornwall (fig. 685). The two larger prismatic crystals in this 
 
 Fig. 685. 
 
 Porphyritic granite. Land's End, Cornwall. 
 
 drawing represent felspar, smaller crystals of which are also seen, similar 
 in form, scattered through the base. In this base also appear black 
 specks of mica, the crystals of which have a more or less perfect hex- 
 agonal 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. 
 
 * Bulletin, 2d sfcrie, iv. 1304; and Archiac, Hist, des Progres de Geol., i. 38. 
 t Delesse, Ann. des Mines, 1852, t, iii. p. 409, and 1848, t xiii. p. 675. 
 
564 PASSAGE OF [Oa XXXIIL 
 
 The uniform mineral character of large masses of granite seems tc 
 indicate that large quantities of the component elements were thoroughly 
 mixed up together, and then crystallized under precisely similar condi- 
 tions. There are, however, many accidental, or " occasional," minerals, 
 as they are termed, which belong to granite. Among these black schorl 
 or tourmaline, actinolite, zircon, garnet, and fluor spar, are not uncom- 
 mon ; but they are too sparingly dispersed to modify the general aspect 
 of the rock. They show, nevertheless, that the ingredients were not 
 everywhere exactly the same ; and a still greater variation may be traced 
 in the ever-varying proportions 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 cele- 
 brated ancient quarries of Syene in Egypt. It has all the appearance of 
 ordinary granite, except where mineralogically examined in hand specimens, 
 and is fully entitled to rank as a geological member of the same plutonic 
 family as granite. Syenite, however, after maintaining the granitic char- 
 acter throughout extensive 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 Scotland and in 
 Guernsey. 
 
 Talcose granite, or Protogine of the French, is a mixture of felspar, 
 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 com- 
 paratively 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 color, it becomes a felspathic granite, called " whitestone" (Weis- 
 stein) 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 favor 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. 
 * Boase on Primary Geology, p. 16. 
 
CH. XXXIIL] GRANITE INTO TRAP. 565 
 
 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. 475) ; 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 further ex- 
 amination for on this subject we have yet much to learn that the pres- 
 ence of these elements in certain proportions is more favorable 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 differ- 
 ent circumstances, 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 sye- 
 nitic-greenstones may doubtless form granite and syenite, if the crystal- 
 lization 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 atmo- 
 sphere. Boutigny's experiments have shown that melted matter, at a 
 white heat, requires to have its temperature lowered before it can va- 
 pourize 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 fossilife- 
 rous 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 be- 
 tween them. 
 
 "The ordinary granite of Aberdeenshire," says Dr. MacCulloch, "is 
 the usual ternary compound of quartz, felspar, and mica; but some- 
 times hornblende is substituted for the mica. But in many places a 
 variety occurs which is composed simply of felspar and hornblende ; and 
 in examining more minutely this duplicate compound, it is observed in 
 some places to assume a fine grain, and at length to become undistin- 
 guishable 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 
 basalif 
 
 In Hungary, there are varieties of trachyte, which, geologically 
 
 * E. de Beaumont, Bulletin, vol. iv. 2d ser. pp. 1318 and 1820. 
 * f Syst. of GeoL voL i. pp. 157, 158. 
 
566 
 
 BOCKS ALTERED BY 
 
 [Cn. XXXIII 
 
 ing, 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 penetrated 
 by plutonic rocks have suffered changes very similar to those exhibited 
 near the contact of volcanic dikes. Thus, in Glen Tilt, in Scotland, al- 
 ternating 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. 687, the undulating outline of the 
 
 Fig. 686. Fig. 687. 
 
 Junction of granite and argillaceous schist in Glen 
 Tilt. (MacCulloch.)* 
 
 (MacCulloch.)* 
 
 granite intersecting d inherent 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 reticu- 
 late the limestone and schist, the veins diminishing towards their termi- 
 nation to the thickness of a leaf of paper or a thread. In some 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 ap- 
 proximates to the granite, particularly where it is penetrated by the 
 smaller veins, the crystalline texture disappears, and it assumes an ap- 
 pearance exactly resembling that of hornstone. The associated argilla- 
 ceous schist often passes into hornblende slate, where it approaches very 
 near to the granite, f 
 
 Geol. Trans., 1st series, vol. iii. pi. 21. 
 
 f MacCulloch, Geol. Trans., vol. iii. p. 259. 
 
CH. XXXIII.] 
 
 GRANITE VEINS. 
 Kg. 633. 
 
 567 
 
 
 Junction of granite and limestone in Glen Tilt. (MacCulloch.) 
 
 Fig. 689. 
 
 The conversion of the limestone in these and many other instances 
 into a siliceous rock, effervescing slowly with acids, would be difficult 
 of explanation, were it not ascertained that such limestones are always 
 impure, containing grains 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 Mount 
 Battock, one of the Grampians, the opposite 
 walls sometimes preserving an exact paral- 
 lelism for a considerable distance. 
 
 As a general rule, however, granite veins 
 Granite veins traversing clay slate in all quarters of the globe are ni ore sinuous 
 Hope* Mountain ' Cape of Goo<i 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. 
 
 * Capt. B. Hall, Trans. Roy. Soc. Edin., vol. vii. 
 
568 
 
 MINERAL STRUCTURE OF 
 
 [On. XXXIII 
 
 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 composed 
 of hornblende, mica, felspar, and 
 quartz, is of a dark color, and is 
 seen underlying gneiss. The other 
 is a red granite, which penetrates 
 the dark variety everywhere in 
 veins.* 
 
 The accompanying sketches will explain the manner in which granite 
 veins often ramify and cut each other (figs. 690 and 691). They repre- 
 
 Fig. 691. 
 
 Granite veins traversing gneiss, Capo Wrath. 
 
 Granite veins traversing gneiss, at Cape Wrath, in Scotland. (MacCulloch.) 
 
 sent 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 fel- 
 spar. In other varieties quartz prevails to the almost entire exclusion 
 both of felspar and mica j in others, the mica and quartz both disappear. 
 and the vein is simply composed of white granular felspar. J 
 
 * MacCulloch, Syst. of Geol., vol. i., p. 58. f Western Islands, pi. 31. 
 J On Geol. of Cornwall, Camb. Trans., vol. i. p. 124. 
 
CH. XXXIII. ] 
 
 GRANITE IN VEINS. 
 
 569 
 
 Fig. 692 is a sketch of a group of granite veins in Cornwall, given 
 by Messrs. Von Oeynhausen and Von Dechen.* The main body of the 
 
 Fig. 692. 
 
 Granite -veins passing through hornblende slate, Carnsilyer Cove, Cornwall. 
 
 granite here is of a porphyritic appearance, with large crystals of fel- 
 spar ; 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 Switzerland, 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. 
 
 Fig. 698. 
 
 Veins of granite in talcose gneiss. (L. A Necker.) 
 
 It is here remarked, that the schist and granite, as they approach, 
 seem to exercise a reciprocal influence on each other, for both undergo a 
 modification of mineral character. The granite, still remaining unstra- 
 tified 7 becomes charged with green particles; and the talcose gneiss 
 assumes a granitiform structure without losing its stratification.f 
 
 * Phil. Mag. and Annals, No. 27, new series, March, 1829. 
 f Necker, sur de Val. de Valorsine, Me'm. de la Soc. de Phys. de Geneve, 1828. 
 I visited, in 1832, the spot referred to in fig. 693. 
 
570 ISOLATED MASSES OF GRANITE. [Cn. XXXIIL 
 
 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 sometimes the existence of rents in 
 other rocks in the vicinity, may have caused the sublimation of the me- 
 tals.* 
 
 There are many instances, as at Markerud, near Christiania, in Nor- 
 way, 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 repiy, tnat 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.f 
 
 The real or apparent isolation of large or small masses of granite de- 
 tached from the main body, as at a , fig. 694 and above, fig. 688, and 
 
 Fig. 694 
 
 General view of junction of granite, and schist of the Valorsine. 
 (L. A. Necker.) 
 
 a, fig. 693, has been thought by some writers to be irreconcilable 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 fusi- 
 ble than the rest, or more fitted to combine readily into some form of 
 granite. 
 
 * Necker, Proceedings of Geol. Soc., No. 26, p. 392. 
 
 f See Keilhau's Gaoa Norvegica; Christiania, 1838. 
 
CH. XXXIII. ] 
 
 CONFORMABLE PORPHYRIES. 
 
 671 
 
 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 subse- 
 quently 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 alternat- 
 ing 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 encrusted with transpa- 
 rent crystals of quartz, the middle of the vein being filled up with com- 
 mon opaque white quartz. 
 
 Fig. 695. 
 
 Gnt-i". 
 
 Gneiss. 
 
 We have seen that the volca- 
 nic 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 indi- 
 cated is highly characteristic. 
 It was indeed supposed by some 
 
 a, &. Quartz rein passing through gneiss and green- of the earlier observers, that the 
 stone, Tronstad Strand, near Christiania. * ^^ of Christiania , in Nor . 
 
 way, was intercalated in mountain masses between the primary or paleo- 
 zoic strata of that country, so as to overlie fossiliferous shale and lime- 
 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 observations on this contro- 
 verted point I had opportunities in 1837 of verifying. There are, how- 
 ever, 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 porphyries (ac, 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 b, and may lead us to suspect that the others 
 
572 GRANITE ROCKS. [Cir. XXXIII. 
 
 also, notwithstanding their appearance of interstratification, have been 
 forcibly injected. Some of the porphyritic rocks above mentioned are 
 highly quartzose, others very felspathic. In proportion as the masses 
 are more voluminous, they become more granitic in their texture, less 
 conformable, and even begin to send forth veins into contiguous strata. 
 In a word, we have here a beautiful illustration of the intermediate gra- 
 dations between volcanic and plutonic rocks, not only in their mineral- 
 ogical composition and structure, but also in their relations of position 
 to associated formations. If the term overlying can in this instance be 
 applied to a 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 volca- 
 no extends downwards to indefinite depths, must produce simultaneously 
 very different effects near the surface, and far below it j and we cannot 
 suppose that rocks resulting from the crystallizing 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 particulars, 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 moun- 
 tain chains volcanic dikes passing^lipwards into lava, 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 demon- 
 strated to have occurred at former periods, will reconcile the student to 
 the belief that crystalline rocks of high antiquity, although deep in the 
 earth's crust when originally formed, may have become uncovered and 
 exposed at the surface. Their actual elevation above the sea may be re- 
 ferred 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. 
 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 composi- 
 tion Test by included fragments Recent and Pliocene ply tonic 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 pre- 
 pared to encounter greater difficulty in ascertaining the precise age of 
 such rocks, than in the case of volcanic and fossiliferous formations. 
 We must bear in mind, that the .evidence of the age of each contempo- 
 raneous volcanic rock was derived, either from lavas poured out upon the 
 ancient surface, whether in the sea or in the atmosphere, or from tuffs 
 and conglomerates, also deposited at the surface, and either containing 
 organic remains themselves, or intercalated between strata containing 
 fossils. But all these tests fail when we endeavour to fix the chrono- 
 logy of a rock which has crystallized from a state of fusion in the bowels 
 of the earth. In that case, we are reduced to the 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 gra- 
 nite ; in Auvergne, where the fresh-water Eocene strata, and at Heidel- 
 berg, on the Rhine, where the New Red sandstone, occupy a similar 
 place. In all these, and similar instances, inferiority in position is con- 
 nected with the superior antiquity of granite. The crystalline rock was 
 solid before the sedimentary beds were superimposed, 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. 567), it is clear that, like intrusive traps, they are 
 newer than the strata which they invade and alter. Examples of the 
 application of this test will be given in the sequel. 
 
 Test by mineral composition. Notwithstanding a general uniformity 
 in the aspect of plutonic rocks, we have seen in the last chapter that 
 
57,1: RECENT AND PLIOCENE [Cn. XXXIV. 
 
 there are many varieties, such as Syenite, Talcose granite, and others 
 One of these varieties is sometimes found exclusively prevailing through- 
 out an extensive region, where it preserves a homogeneous character ; so 
 that having ascertained its relative age in one place, we can easily recog- 
 nize 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 xhan com- 
 mon or micaceous granite. But modern investigations have proved these 
 generalizations to have been premature. The syenitic granite of Nor- 
 way 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 consisting of mica, 
 quartz, and felspar, is newer than the coal. (See p. 580.) 
 
 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 Ame- 
 rica, 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, why invisible. The explanation 
 already given in the 29th and in the last chapter, of the probtfble rela- 
 tion 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 uncommon 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 accu- 
 mulated in some places to the height of 550 feet, was found to retain a 
 high temperature half a century after the eruption. f "VVe 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 extremely gradual. Sometimes, in- 
 deed, this process may be retarded for an indefinite period, by the acces- 
 sion 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 
 
 * Silliman's Journ., No. 69, p. 123. f See " Principles," Index, " Jorullo." 
 
CH. XXXIV.] PLUTONIC ROCKS. 575 
 
 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 liquefac- 
 tion. 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 considerable antiquity relatively 
 to the fossiliferous and volcanic formations, before it becomes extensively 
 visible. As we know that the upheaval of land has been sometimes 
 accompanied in South America by 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 suc- 
 cessively below, subterposition 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 formations 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 pro- 
 duced the newer plutonic rocks Nos. II., III., 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 convulsions 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 time 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. 230), the great nummulitic formation of the Alps and Pyrenees was 
 
 * " Principles," Index, " Volcanic Eruptions." 
 
576 
 
 PLUTONIC ROCKS. 
 
 [CH. XXXIV, 
 
 1 fill 
 
 Zp/p-S 
 
 S ftt^S 
 
 frS** 
 
 o ^o S~3 
 
 to P^MHrt 
 
 I H 'w'av* 
 
 ,2 M M 
 
 i 
 I 
 
 I! 
 
CH. XXXIV.] PLUTONIC BOCKS OF THE ANDES. 577 
 
 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 por- 
 tion 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 the flysch was de- 
 posited 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, therefore, 
 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 calcareous clay-slates, rising to the height of 
 nearly 14,000 feet above the sea, in which are shells of the genera Gry- 
 phaea, Turritetta, Terebratula, and Ammonite. These rocks are sup- 
 posed 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 plutonic 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 con- 
 glomerates, of vast thickness, the materials of which are derived from 
 the ruins of the western chain. The pebbles of the conglomerates 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 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 terti- 
 ary formations. 
 
 Darwin, pp. 390, 406; second edition, p. 319. 
 37 
 
578 VOLUME OP HIDDEN PLUTONIC ROCKS. [On. XXXIV. 
 
 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, in the nether regions, of plutonic and 
 metamorphic rocks, and their emergence at the surface. For a long 
 series of subterranean movements must occur before such rocks can be 
 uplifted into the atmosphere or the ocean ; and, before they can be ren- 
 dered visible to man, some strata which previously covered them must 
 usually have been stripped off by denudation. 
 
 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 other 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*, 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 either become the 
 receptacles of sunken fragments of the earth's crust, or have been ren- 
 dered 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 
 
 * See map of Europe and explanation, in Principles, book L 
 
CH. XXXIV.] PLUTONIC ROCKS OF OOLITE AND LIAS. 570 
 
 have occurred in the earth's crust within an equal quantity of time an- 
 terior to the Eocene epoch. They who contend for the more intense 
 energy of subterranean causes in the remoter eras of the earth's history, 
 may find it more difficult to give an answer to this question than they 
 anticipated. 
 
 The principal effect of volcanic action in the nether regions, during 
 the tertiary period, seems to have consisted in the upheaval to the sur- 
 face of hypogene formations of an age anterior to the carboniferous. 
 The repetition of another series of movements, of equal violence, 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 meta- 
 morphic 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. 
 Pig. 69S. Suppose b, GJ d, to be three members of 
 
 the Cretaceous series, the lowest of which, 
 b, has been altered by the granite A, the 
 modifying influence not having extended 
 so far as c, or having but slightly affected 
 its lowest beds. Now it can rarely be 
 possible for the geologist to decide whether 
 the beds d existed at the time of the intrusion of A, and alteration of 
 b and c, or whether they were subsequently thrown down upon c. 
 
 But as some cretaceous and even tertiary rocks have been raised to 
 the height of more than 9000 feet in the Pyrenees, we must not assume 
 that plutonic formations of the same periods may not have been brought 
 up and 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 texture, but 
 is extremely fine-grained. When nearer the junction it becomes gray, 
 and has a saccharoid structure. In another locality, near Champoleon, a 
 granite composed of quartz, black mica, and rose-colored 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 the altered 
 
580 
 
 PLUTONIC ROCKS OF THE 
 
 [Cn. XXXIT. 
 
 J unction of granite with Jurassic or Oolite strata in 
 the Alps, near Champoleon. 
 
 mass the argillaceous beds are 
 hardened, the limestone is sac- 
 charoid ; the gritz quartzose, 
 and in the midst of them is a 
 thin layer of an imperfect 
 granite. It is also an impor- 
 tant 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 gra- 
 nite, 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. J 
 
 At Predazzo, in the Tyrol, secondary strata, some of which are lime- 
 stones of the Oolite period, have been traversed and altered by plutonic 
 rocks, one portion of which is an augitic porphyry, which passes insen- 
 sibly into granite. The limestone is changed into granular 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 true coal- 
 plants, are regarded by Professor Sedgwick and^Sir K. Murchison as 
 members of the true carboniferous series. This granite, like the syeni- 
 tic granite of Christiania, has broken through the stratified 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 
 
 * Elie de Beaumont, sur les Montagnes de 1'Oisans, &c. M6m. de la Soc. 
 1'Hist. Nat. de Paris, torn. v. 
 
 f See Murchison, Geol. Trans., 2d series, vol. ii., part ii., pp. 311 321. 
 J Western Islands, vol. i. p. 330, plate 18, figs. 3, 4. 
 Von Buch, Annales de Chimie, &c. 
 
CH. XXXIV.] CARBONIFEROUS AND SILURIAN PERIODS. 
 
 581 
 
 also penetrated by granite veins, and plutonic dikes, called " el vans."* 
 The granite of Cornwall is probably 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 neai 
 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. 572.) Von Buch supposed that the 
 plutonic rock alternated with the fossiliferous strata, and that large 
 masses of granite *?ere 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, ap- 
 pearing as if they would pass under it in mass, as .it a, fig. 700, and 
 then again on the opposite side of the same mountain, as at b, dip away 
 from the same granite. When the junctions, however, are carefully 
 examined, it is found that the plutonic rock 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 formation 
 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 beds, rest unconformably upon the trun- 
 cated edges of the gneiss, the inclined strata of which had been 
 denuded before the sedimentary beds were superimposed (see fig. 
 701). The signs of denudation are twofold; first, the surface of the 
 
 Fig. 701. 
 
 Gneiss. . Granite. Gneiss. 
 
 Granite sending veins into Silurian strata and Gneiss, Christiania, Norway. 
 
 * Proceed. Geol. Soc. voL il p. 562, and Trans. 2d ser. vol. v. p. 686. 
 f See the Gaea Norvegica and other works of Keilhau, with whom I examined 
 this country. 
 
582 PROTRUSION OF SOLID GRANITE. [On. XXXIY. 
 
 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 fou-nd in some of the Silurian strata. Between the origin, 
 therefore, of the gneiss and the granite there intervened, first, the period 
 when the strata of gneiss were denuded ; 2dly, the period of the deposition 
 of the Silurian deposits. 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 tad 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 injec- 
 tion 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 alterations 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. 452, 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 become metamorphic. If we find pebbles of granite in a con- 
 glomerate 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 
 
CH. XXXIV.] AGE OF GRANITES OF ARRAN. 583 
 
 at a period subsequent to the deposition of those strata.* Professor 
 Sedgwick and Sir R. Murchison conceive that this granite has been up- 
 heaved in a solid form ; and that in breaking through the submarine 
 deposits, with which it was not perhaps originally in contact, it has frac- 
 tured them so as to form a breccia along the line of junction. This 
 breccia consists of fragments of shale, sandstone, and limestone, with 
 fossils of the oolite, all united together by a calcareous cement. The 
 secondary strata, at some distance from the granite, are but slightly dis- 
 turbed, but in proportion to their proximity the amount of dislocation 
 becomes greater. 
 
 If we admit that solid hypogene rocks, whether stratified or unstrati- 
 fied, 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,! 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, plutonic, and 
 metamorphic, are all conspicuously displayed within a very small area, 
 and with their peculiar characters strongly contrasted. 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 metamorphic 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 conglom- 
 erate and sandstone (No. 3), which are referable to the Old Red forma- 
 tion, 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 conjectured 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 
 
 * Murchison, Geol. Trans., 2d series, vol. ii. p. 307. 
 f Geognostiche Wanderungen, Leipzig, 1838. 
 
584 AGE OF THE GRANITES. [On. XXXIV 
 
 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 
 associated with the trap formation, and sending veins into the sandstone 
 or into the upper strata of No. 4. This interesting discovery of granite 
 in the southern region of Arran, at a point where it is separated from 
 the northern mass of granite by a great thickness of secondaiy strata 
 and overlying trap, was made by Mr. L. A. Necker of Geneva, during 
 his survey of Arran, in 1839. We also learn from late investiga- 
 tions by Professor A. C. Ramsay, that a similar fine-grained granite (No. 
 6 6) 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 5) may be of the same 
 age as that of Ploverfield (No. 6 a), 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. 1), into which it sends veins. 
 
 An objection may perhaps at first be started to this conclusion, de- 
 rived from the curious and striking fact, the importance of which wa^ 
 first emphatically pointed out by Dr. MacCulloch, that no pebbles of 
 granite occur in the conglomerates of the red sandstone in Arran, though 
 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 occurring in the immediate vicinity. 
 The total absence therefore of granitic 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 conglomerates of No. 4 have any granitic fragments 
 been discovered. Are we then entitled to affirm that the coarse-grained 
 granite (No. 2), like 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 conglomerate 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 invaded 
 by granite ? This opinion, although not inadmissible, is by no meang 
 
Ctt. XXXI V.I 
 
 OF THE ISLE OF ARRAN. 
 
 585 
 
586 GRANITES OF ARRAN. [Cu. XXSIV, 
 
 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 
 
 Fig. 703. 
 Sea 
 
 torrents and rivers descended, carrying down gravel and sand. The 
 plutonic rock or granite (B) may even then have lten previously in- 
 jected 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 6). 
 
 We have shown that these eruptions, whatever their date, were poste- 
 rior to the deposition of all the fossiliferous strata of Arran. We can 
 also prove that subsequently both the granitic and trappean rocks under- 
 went great aqueous denudation, which they probably suffered during 
 their emergence from the sea. The fact is demonstrated by the abrupt 
 truncation of numerous dikes, such as those at c, c?, 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 neces- 
 sity of supposing that both the trap and the conglomerate once extended 
 farther, and that veins such as c, ^, 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 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 hypothesis of a great amount of 
 movement at that point where the granite is supposed to have been 
 
CH. XXXV.] METAMOKPHIC ROCKS. 587 
 
 thrust up bodily, and where we may conceive it to have been dis- 
 tended laterally by the repeated injection of fresh supplies of melted 
 materials.* - 
 
 CHAPTER XXXV. 
 
 METAMORPHIC ROCKS. 
 
 General character of metamorphic rocks Gneiss Hornblende-schist Mica- 
 schist Clay-slate Quartzite Chlorite-schist Metamorphic limestone Al- 
 phabetical 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 mem- 
 bers 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 plu- 
 tonic, 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 opin- 
 ion that such strata, after having been deposited from water, acquired, by 
 the influence of heat and other causes, a highly crystalline texture. They 
 who still question this opinion may call the rocks under consideration the 
 stratified hypogene, 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" formations, 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 succession 
 
 * For the geology of Arran consult the works of Drs. Hutton and MacCulloch, 
 the Memoirs of Messrs. Von Dechen and Oeynhausen, that of Professor Sedgwick 
 and Sir R. Murchison (Geol. Trans. 2d series), Mr. L. A. decker's Memoir, read to 
 the Royal Soc. of Edin. 20th April, 1840, and Mr. Ramsay's Geol. of Arran, 1841. 
 I examined myself a large part of Arran in 1836. 
 
588 GNEISS HORNBLENDE-SCHIST. [On. XXXV 
 
 or superposition in the members of this family ; clay-slate, for example, 
 having been often supposed to hold invariably a higher geological posi- 
 tion than mica-schist, and mica-schist always to overlie gneiss. But 
 although such an order may prevail throughout limited districts, it is 
 by no means universal. To this subject, however, I shall again revert, in 
 the 37th chapter, when the chronological 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 ma- 
 terials as granite, ramely, felspar, quartz, and mica. In the specimen 
 here figured, the white layers consist almost exclusively of granular fel- 
 spar, with here and there a speck of mica and grain of quartz. The dark 
 layers are composed of gray quartz and black mica, with occasionally a 
 
 Fig. 704. 
 
 Fragment of gneiss, natural size: section made at right angles to 
 the planes of foliation. 
 
 grain of felspar intermixed. The rock splits most easily in the plane of 
 these darker layers, and the surface thus exposed is almost entirely cov- 
 ered with shining spangles of mica. The accompanying quartz, however, 
 greatly predominates in quantity, but the most ready cleavage is deter- 
 mined by the abundance of mica in certain parts of the dark layer. 
 
 Instead of consisting of these thin laminae, gneiss is sometimes simply 
 divided into thick beds, in which the mica has only a slight degree of 
 parallelism to the planes of stratification. 
 
 The term " gneiss," however, in geology is commonly used in a wider 
 sense, to designate a formation in which the above-mentioned rock pre- 
 vails, 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). 
 
CH. XXXV.] MICA-SCHIST, CLAY-SLATE, ETC. 589 
 
 Hornblende-schist is usually black, and composed principally of horn- 
 blende, with a variable quantity of felspar, and sometimes grains 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 com- 
 posed of mica and quartz, the mica sometimes appearing to constitute the 
 whole mass. Beds of pure quartz also occur in this format* on. 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-gray to a lead color ; and it may be said of 
 this, more than of any other schist, that it is common to the metamorphic 
 and fossiliferous series, for some clay-slates taken from each division would 
 not be 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 graduating 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 t it occurs in thin beds, forming a foliated schist much 
 resembling in color and appearance certain varieties of gneiss and mica- 
 schist. When it alternates with these rocks, it often contains some crys- 
 tals 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 de- 
 veloped 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. 
 
590 METAMORPHIC EOCKS. [On. XXXV. 
 
 Explanation of the Names, Synonyms, and Mineral Composition of tht 
 more abundant Metamorphic Rocks. 
 
 ACTINOLITE-SCHIST. A slaty foliated rock, composed chiefly of actinolite (an emer- 
 ald-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. 589. 
 
 ARKOSE. Name given by Brongniart to a compound of the same materials as 
 granite, which it xrften 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 fclender rhomboidal crystals. For composition, see Table, p. 475. 
 
 CHLORITE-SCIIIST. A green slaty rock, in which chlorite, a green scaly mineral, is 
 abundant. See p. 589. 
 
 CLAY-SLATE or ARGILLACEOUS-SCHIST. See p. 589* 
 
 EURITE has been already mentioned as a plutonic rock (p. 564), 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. 589. 
 
 HORNBLENDE ROCK, or AMPHIBOLITE. See above, p. 473. A member both of the 
 volcanic and metamorphic series. Agrees in composition with hornblende- 
 schist, but is not fissile. 
 
 HORNBLENDE-SCHIST, or SLATE. Composed of hornblende and felspar. See p. 589. 
 
 HORNBLENDIC or SYENiTic GNEISS. Composed of felspar, quartz, and hornblende. 
 
 HYPOGENE LIMESTONE. See p. 589. 
 
 MARBLE. See pp. 12 <fe 589. 
 
 MICA-SCHIST, or MICACEOUS- SCHIST. A slaty rock, composed of mica and quartz, in 
 
 variable proportions. See p. 589. 
 MICA-SLATE. See MICA-SCHIST, p. 589. 
 
 PHYLLADE. D'Aubuisson's term for clay-slate, from 0uAXa?, a heap of leaves. 
 
 PRIMARY LIMESTONE. See HYPOGENE LIMESTONE, p. 589. 
 
 PROTOGINE. See TALCOSE- GNEISS, p. 588; when unstratified it is Talcose-granite. 
 
 QUARTZ ROCK, or QUARTZITE. A stratified rock ; an aggregate of grains of quartz. 
 See p. 589. 
 
 SERPENTINE has already been described (p. 474), 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. 588. 
 TALCOSE-SCHIST consists chiefly of talc, or of talc and quartz, or of talc and fel 
 
 spar, and has a texture something like that of clay-slate. 
 
CH. XXXV.] METAMOKPHIC KOCKS. 591 
 
 Origin of the Metamorphic Strata. 
 
 Having said thus much of the mineral composition of the metamorphic 
 rocks, I may combine what remains to be said of their structure and his- 
 tory with an account of the opinions entertained of 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 specu- 
 lations. It was once a favorite 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 con- 
 dition 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 deposited as sediment from 
 water. The general adoption by geologists of the term stratified, as 
 applied to these rocks, sufficiently attests their division into beds very 
 analogous, at least in form, to ordinary fossiliferous strata. This resem- 
 blance is by no means confined to the existence in both occasionally of 
 a laminated structure, but extends to every kind of arrangement which 
 is compatible with the absence of fossils, and of sand, pebbles, ripple- 
 mark, and other characters which the metamorphic theory supposes 
 to have been obliterated by plutonic action. Thus, for example, we 
 behold alike in the crystalline and fossiliferous formations an alternation 
 of beds varying greatly in composition, color, and thickness. We 
 observe, for instance, gneiss alternating with layers of black hornblende- 
 schist, or of green chlorite-schist, or with granular quartz, or 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 granu- 
 lar 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 neighborhood of granite. It will be 
 useful here to add other illustrations, showing that a texture undis- 
 tinguishable from that which characterizes the more crystalline meta- 
 morphic formations has actually been superinduced in strata once fos- 
 siliferous. 
 
592 
 
 STEATA IN" CONTACT WITH GRANITE. [On. XXXY. 
 
 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 pro- 
 trudes 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 sand- 
 stone, and all these are invariably altered near the granite for a dis- 
 tance of from 50 to 400 yards. The aluminous shales are hardened and 
 have become flinty. Sometimes ' they resemble jasper. Ribboned jasper 
 is produced by the hardening of alternate layers of green and chocolate- 
 colored schist, each stripe faithfully representing the original lines of strati- 
 fication. Nearer the granite the schist often contains crystals of horn- 
 blende, which are even met with in some places for a distance of several 
 hundred yards from the junction ; and this black hornblende is so abun- 
 dant 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 crystalline 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 color, 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 al- 
 
 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. 
 
 tered limestone and hardened slate contain garnets in many places, 
 also ores of iron, lead, and copper, with some silver. These altera- 
 tions occur equally, whether the granite invades the strata in a line 
 parallel to the general strike of the fossiliferous beds, or in a line al 
 
CH. XXXV ALTERATIONS OF STRATA. 593 
 
 right angles to their strike, as will be seen by the accompanying ground 
 plan.* 
 
 The indurated and ribboned schists above mentioned bear a strong re- 
 semblance to certain shales of the coal found at Russel's Hall, near Dud- 
 ley, where coal-mines have been on fire for ages. Beds of shale of con- 
 siderable 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-colored. 
 
 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 appear- 
 ances are well seen at the junction of the granite and killas, in St. 
 Michael's Mount, a small island nearly 300 feet high, situated in the bay, 
 at a distance of about three miles from Penzance. 
 
 The granite of Dartmoor, in Devonshire, says Sir H. de la Beche, 
 has intruded itself into the slate and slaty sandstone called greywacke, 
 twisting and contorting the strata, and sending veins into them. Hence 
 some of the slate rocks have become " micaceous ; others more indu- 
 rated, and with the characters of mica-slate and gneiss ; while others 
 again appear converted into a hard-zoned rock strongly impregnated 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 neighborhood 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 contained in abundance. At some points, also, 
 it becomes dolomitic, and filled with small veins of carbonate of iron, and 
 spots of red iron-ore. At Rancie the lias nearest the granite is not only 
 filled with iron-ore, but charged with 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 vol- 
 canic 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 character, similar to, nay, 
 often absolutely identical with that of gneiss, mica-schist, and other strati- 
 fied 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 trans- 
 mutation, if, for reasons before explained, we concede the igneous origin 
 of granite. 
 
 * Keilhau, Gaea Norvegica, pp. 61-63. f GeoL Manual, p. 479. 
 
 38 
 
594 PLUTONIC ACTION. [On. XXXV 
 
 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 ob- 
 literated. 
 
 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. While the materials of granite, there- 
 fore, came in contact with the fossiliferous stratum in the bowels of the 
 earth under great pressure, the contained gases might be unable to eseape ; 
 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 sulphuretted hydrogen, muriatic acid, and car- 
 bonic acid, issue in many places from rents in rocks, which they have 
 discolored 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 a hydrostatic 
 pressure of 96 feet, will absorb three times as much carbonic acid gas as 
 it can under the ordinary pressure of the atmosphere. 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 Pro- 
 fessor 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 con- 
 ceivable 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 containing 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 satu- 
 rated with free carbonic acid gas ; which gas rises plentifully from the 
 soil there and in many parts of the surrounding country. The various 
 elements of the gneiss, with the exception of the quartz, are all softened ; 
 
 * Phil. Trans. 1804. 
 
 f Poggendorf s Annalen, No. xvi. 2d series, vol. iii. 
 
CH. XXXV.] ROCKS ALTERED BY SUBTERRANEAN GASES. 595 
 
 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 discolored in various places, and 
 strangely altered by the " all-penetrating vapors." Dark clays have be- 
 come 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 chalce- 
 dony and opal, and others of fibrous gypsum, have resulted from these 
 volcanic exhalations.! 
 
 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 decom- 
 position 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 exter- 
 nal air. The extent, therefore, of the earth's crust which the vapors have 
 permeated and are now permeating may be thousands of fathoms in thick- 
 ness, and their heating and modifying influence may be spread through- 
 out 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 bow- 
 els of the earth, having a temperature equal or even greater than 
 the melting point of lava, and having an elasticity of which even Pa- 
 pin's digester can give but a faint idea, may convert rocks into liquid 
 matter. || 
 
 The above observations are calculated to meet some of the objections 
 which have been urged against the metamorphic theory on the ground 
 of the small power of pocks 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 which extend merely for a 
 few feet from the contact of a dike could have penetrated through moun- 
 
 * See Principles, Index, " Carbonated Springs," Ac. 
 f Hoffmann's Liparischen Inseln, p. 38. Leipzig, 1832. 
 
 J See Princ. of Geol. ; and Bulletin de la Soc. G6ol. de France, torn, ii 
 p. 230. 
 
 See Princ. of GeoL; and Daubeny's Volcanos, p. 167. 
 jj Jam. Ed, New Phil. Journ. No. 51, p. 43. 
 
596 ORIGIN" OF METAHORPHIC STRUCTURE. [On. 
 
 tain masses of crystalline strata several miles in thickness. Now it has 
 been stated that the plutonic influence of the syenite of Norway has some- 
 times 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. 593.) 
 This is undoubtedly an extreme case ; but is it not far more philosophical 
 to suppose that this influence may, under favorable circumstances, 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 in- 
 terior 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 semi-fusion, so that on cooling they have become crys- 
 talline, 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 forma- 
 tions, and the conversions which can be ascertained 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 
 limestone, replete with shells and corals, which have since been obliter- 
 ated ; 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 6f texture."* " In Shetland," remarks the same author, 
 " argillaceous-schist (or clay-slate), when in contact with granite, is some- 
 times 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 igneous roclis, 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 im- 
 pure anthracite occurs, interstratified with mica-schist. It is about 2 feet 
 
 * Syst. of Geol. vol. i. p. 210 f ^id. p. 211. 
 
 J &ee above, p. 388, 394. 
 
CH. XXXV.] 'ORIGIN OF METAMORPHIC STRUCTURE. 597 
 
 in thickness, and has been made use of both as fuel, and in the manu 
 facture 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, Neu- 
 ropteris, Calamites, &c. This anthracite is intermediate in character be- 
 tween 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 carbonif- 
 erous shales or slates with anthracite and plants, which in Rhode Island 
 often pass into mica-schist, have at Worcester assumed a perfectly crys- 
 talline and metamorphic texture ; the anthracite having been nearly trans- 
 muted into that state of pure carbon which is called plumbago or 
 graphite.* 
 
 It has been remarked by M. Delesse that the minerals developed in 
 hypogene limestone vary according to the degree of metamorphism 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, horn- 
 blende, Wollastonite, dipyre, Couzeranite, and some others appear ; and, 
 lastly, where the crystallization 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 nat- 
 urally expect to meet with silicates of alumina in crystalline limestone ; 
 such silicates, accordingly, are frequent, and occasionally even pure alumi- 
 na crystallized in the form of corundum.f 
 
 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 original matrix. 
 
 The total absence of any trace of fossils has inclined many geologists 
 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 occur. But in urging this argu- 
 ment, it seems to have been forgotten that there are stratified formations 
 of enormous thickness, and of various ages, and some of them very mod- 
 ern, all formed after the earth had become the abode of living creatures, 
 which are, nevertheless, in certain districts, entirely destitute of all ves- 
 tiges of organic bodies. In some, the traces of fossils may have been 
 effaced by water and acids, at many successive periods ; and it is clear, 
 
 * See Lyell, Quart. GeoL Journ. vol. i. p. 199. 
 
 f Delesse, Bulletin Soc. GeoL France, 2d serie, torn. 9, p. 126. 1851. 
 
598 OBJECTIONS TO METAMORPHIC THEOKY. [Cn. XXXV. 
 
 that, the older the stratum, the greater is the chance of its being non- 
 fossiliferous, 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 de- 
 composition. But this reasoning 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 ap- 
 pear 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 pri- 
 mary 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,} the Upper and 
 Lower Silurian in East Canada^ and the clay-slates (of Cambrian date ?) 
 in Norway , all contain as much alkali as is generally present in meta- 
 morphic 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 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 ingre- 
 dient 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 de- 
 gree of heat capable of reducing others to semi-fusion. Nor should it be 
 
 * Dr. Boase, Primary Geology, p. 319. 
 
 f H.Taylor, Edin. New. Phil. Journ. vol. i. 1851, p. 140. 
 
 j Hunt, Phil. Mag. 4 ser. vol. vii. p. 237. 
 
 Kyersly, Norsk, Mag. for Naturvidenp. vol viii. p. 172. 
 
CH. XXXV.] METAMORPEIC THEORY. 500 
 
 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 meta 
 morphic 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 \vithin 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. 230), 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 charac- 
 ter to gneiss.* In this case heat, or vapor, 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-arrangement of 
 the molecules, while the adjoining strata did not give passage to the same 
 heat, or if BO, remained unchanged because they were composed of less 
 fusible materials. Whatever hypothesis we adopt, the phenomena estab- 
 lish beyond a doubt the possibility of the development of the metamor- 
 phic structure in a tertiary deposit in planes parallel to those of stratifi- 
 cation. 
 
 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, Jmrn. yoL v. p. 211 1848. 
 
GOO METAMOKPHIC EOCKS. [Ca XXXVI 
 
 CHAPTER XXXVI. 
 
 Origin of the metamorphic rocks, continued Definition of joints slaty cleavage 
 and foliation Supposed causes of these structures Mechanical theory of 
 cleavage Condensation and elongation of slate rocks by lateral pressure 
 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 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 irregularity in the planes of foliation. 
 
 WE have already seen that crystalline forces of great intensity have 
 frequently acted upon sedimentary and fossiliferous strata long subse- 
 quently 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 care- 
 fully 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 understanding of this diffi- 
 cult subject, observes, that joints are distinguishable from lines of slaty 
 cleavage in this, that the rock intervening between two joints, has no 
 tendency to cleave in a direction parallel to the planes of the joints ; 
 whereas a rock is capable of 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 
 
 Fig. T06. 
 
 Parallel planes of cleavage intersecting curved strata. (Sedgwick.) 
 
 slate. The true bedding is there indicated by a number of parallel 
 stripes, some of a lighter and some of a darker color than the general 
 
CH. XXXVI. ] JOINTED STRUCTUKE AND CLEAVAGE. 601 
 
 mass. Such stripes are found to be parallel to the true planes of strati- 
 fication, wherever these are manifested by ripple-mark, or by beds con- 
 taining peculiar organic remains. Some of the contorted strata are of a 
 coarse mechanical structure, alternating with fine-grained crystalline 
 chloride 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 w<hen these are very coarse that the cleavage planes entirely 
 vanish. These planes are usually inclined 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 stratifi- 
 cation 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 phenomena, as ex- 
 hibited in Shropshire and the neighboring counties, the greatest aid in 
 the extraction of blocks of stone ; and, if a sufficient number cross each 
 other, the whole mass of rock is split into symmetrical blocks. The 
 faces of the joints are for the most part smoother and more regular than 
 the surfaces of true strata. The joints are straight-cut chinks, often 
 slightly open, often passing, not only through layers of successive depo- 
 sition, but also through balls of limestone or other matter which have 
 been formed by concretionary 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.f 
 
 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. J 
 
 In the Swiss and Savoy Alps, as Mr. Bakewell has remarked, enormous 
 masses of limestone are cut through so regularly by nearly vertical part- 
 ings, 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 horizon tal.( 
 
 Now such joints are supposed to be analogous to the partings which 
 
 * Geol. Trans. 2d series, voL iii. p. 461. 
 
 f Silurian System, p. 246. 
 
 \ Introduction to Geology, chap. iv. 
 
602 JOINTED STKUCTUEE AND CLEAVAGE. [Cn. XXXVL 
 
 Fig. 707. 
 
 Stratification, joints, and cleavage. 
 (From Murchison's Silurian System, p. 245.) 
 
 separate volcanic and plutonic rocks into cuboidal and prismatic masses. 
 On a small scale we see clay and starch, when dry, split into similar 
 shapes ; this is often caused by simple contraction, whether the shrinking 
 be due to the evaporation of water, or to a change of temperature. 
 It is well known that many sandstones 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 temper- 
 ature have probably contributed largely to the production of joints in 
 rocks. 
 
 In some countries, as in Saxony, where masses of basalt rest on sand- 
 stone, 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 internal 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 deposition, declared 
 in the essay before alluded to, his opinion ' that no retreat of parts, no 
 contraction in the dimensions of rocks in passing to a solid state, can 
 account for the phenomenon. He 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 crystalli- 
 zation, 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 nature have a general tendency 
 
CH. XXXVL] SLATY CLEAVAGE. 603 
 
 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 soils of soap, in which insoluble 
 margarates* exist, exhibit the same phenomenon when mixed with 
 water ; and what occurs in our experiments on a minute scale may occur 
 in nature on n 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 dis- 
 tortion, 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 in- 
 quiry, 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 perpendicular to the planes of cleavage, and a correspond- 
 ing 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, a, 6, c, hare 
 remained comparatively unbent. The points d and/ 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 bend- 
 ing ; but, in proof of elongation, it will be observed that the thickness 
 of the bed c?/is now about four times greater in those parts lying in the 
 main direction of the flexures than in a plane perpendicular to them : 
 
 * Margaric acid is an oleaginous acid, formed from different animal and vege- 
 table fatty substances. A margarate is a compound of this acid with soda, 
 potash, or some other base, and is so named from its pearly lustre. 
 
 f Letter to the author, dated Cape of Good Hope, Feb. 20, 1836. 
 
 \ Report, Brit. Assoc., Cork, 1843, Sect p. 60. 
 
 Quart. GeoL Journ. voL iii. p. 87. 1847. 
 
 | On the Origin of Slaty Cleavage, by H. C. Sorby, Edinb. Kew PhiL Journ. 
 1853, vol. Iv. p. 137. 
 
604 
 
 SLATE EOCK OF NORTH DEVON. [On. XXXVL 
 
 Fig. 708 
 
 and the same bed exhibits cleavage- 
 planes in the direction of the great- 
 est movement, 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, 6, and a, must have under- 
 gone an equal amount of pressure 
 with d, the points a and g having 
 approximated as much towards 
 each other as have d and /. The 
 same phenomena are also repeated 
 in the beds below df, and might 
 have been shown, had the section 
 been extending downwards. Hence 
 it appears that the finer beds have 
 been squeezed into a fourth of the 
 space they previously occupied, 
 partly by condensation, or the closer 
 packing of their ultimate particles 
 (which has given rise to the great 
 specific gravity of such slates), and 
 partly by elongation in the line of (Drawn by H. c. Sorby.) 
 
 the dip of the cleavage, Of which Vertical section of slate rock in the cliffs 
 . . near Ilfracombe, North Devon. 
 
 the general direction is perpendicu- 
 
 . . J ., J , //mi 
 
 lar to that of the pressure. " These 
 
 ,-, . -XT j.i_ 
 
 and numerous Other Cases m 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 di- 
 
 mensions. If the whole were then compressed in the direction of the 
 
 length of the strip of paper, it would be bent and puckered up 
 
 into contortions, whilst the plastic material would readily change its 
 
 dimensions without undergoing such contortions; and the difference 
 
 in distance of the ends of the paper, as measured in a direct line or 
 
 along it, would indicate the change in the dimensions of the plastic 
 
 material." 
 
 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 respect- 
 ively 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 
 
 Scale one 
 
 to one foot - 
 
 a i k c i e - Fine-grained slates, the stratifica- 
 tion being shown partly by lighter or dark- 
 
 ditoent degrec3 of 
 
Co. XXXVI] CONDENSATION OF SLATE EOCKS. 605 
 
 dip of the cleavage, or they may have yielded 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 directions. 
 May not their position in the slates have been determined by the 
 movement of elongation before alluded to 1 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 elongation, 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 lamina- 
 tion 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 development 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 imperfect fluidity. 
 In the islands of Ponza and Palmarola, the direction of the zones is more 
 frequently vertical than horizontal, because the mass was impelled from 
 below upwards.f 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 Geol. Trans. 2d ser. vol. ii. p. 227. 
 
606 FOLIATION OF CRYSTALLINE ROCKS. [Cn. XX XVI 
 
 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 colors, alternating again and again, some of them com- 
 posed 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 crystal- 
 lizing force acted more freely in the direction of the planes of cleav- 
 age, produced when the pasty mass was stretched, whether because 
 confined vapors 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 under- 
 stood. 
 
 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 dh'ided. 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 homo- 
 geneous. 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 
 whore 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 con- 
 nected with sedimentary deposition, has impressed cleavage on the one 
 set of rocks and foliation on the other. But such an inference can only 
 be legitimately drawn in those rare cases where we are able, by a con- 
 tinuous 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 strati- 
 fication 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 same 
 direction as the strike of the slaty cleavage ; for the true strata always 
 
 * Darwin, Volcanic Islands, pp. 69, 70. 
 
CH. XXXVI] FOLIATION AXD CLEAVAGE. 607 
 
 dip at right angles to the axis of elevation, and are parallel to it in their 
 strike. No argument, therefore, can be drawn in favor 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 diffi- 
 cult 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 countiy (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 metamor- 
 phic 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 stratifica- 
 tion 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 
 limestone 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 
 colored bands of limestone all dipping, like the foila, 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 mu- 
 tual attraction of like particles to favor the crystallization of the quartz, 
 or mica, or felspar, or carbonate of lime, along the planes of original de- 
 position, ratter 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 b 
 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 ot 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 con- 
 ceives that " foliation may be the extreme result of the process of which 
 
 Norske Mag. BTaturvidsk. vol. i. p. 71. 
 
 f Memoir read before the Geol. Soc., London, Jan. 31, 1855. 
 
 j South America, p. 149. 
 
608 FOLIATION AND CLEAVAGE. [On. XXXVI. 
 
 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 laminse of clay-slate, where 
 they cut straight through the bands of stratification, and therefore indis- 
 putably true cleavage-planes, differ slightly from one another in their 
 grayish and greenish tints of color, as also in their compactness, 
 and in some laminae having a more jrtspery 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 char- 
 acter of the rock in the same planes."* As one step farther towards 
 tracing a passage from planes of cleavage to those of foliation, Pro- 
 fessor 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 
 
 Mr. D. Sharpe inferred from observations made by him in the High- 
 lands 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 man- 
 ner in South America the cleavage planes of the clay-slate had been sus- 
 pected 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 homo- 
 geneous 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 coun- 
 tries 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 deposi- 
 tion, 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 the lamination of the chloritic and other crystalline 
 
 * Geol. Observ. on South America, p. 155. 
 
 f Sedgwick, Geol. Trans. 2d ser. vol. iii. p. 471. 
 
 \ D. Sharpe, Phil. Trans. 1852, and Geol. Quart. Journ. No. 41, 1855. 
 
 Darwin, S. America, p. 155. 
 
CH. XXXVI] IRREGULARITIES IX FOLIATIOX. 609 
 
 schists in Anglesea was approximately in the planes of bedding ; and 
 Professor 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 Forfarshire 
 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 .vs the intercala- 
 tion of masses of limestone, and of chloritic, actinolitic, and horn- 
 blende 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 car- 
 bonate of lime, are more distinct, in certain metamorphic rocks, than 
 the ingredients composing alternate layers in most sedimentary de- 
 posits, 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 reg- 
 ularity. The occurrence of wedge-shaped masses, such as belong to 
 coarse sand and pebbles, diagonal lamination (see p. 16), ripple-mark, 
 unconformable stratification (p. 61), the fantastic folds produced by 
 lateral pressure, faults of various width, intrusive dikes of trap, or- 
 ganic bodies of diversified shapes, and other causes of unevenness in the 
 planes of deposition, both on the small and on the large scale, will inter- 
 fere with parallelism. If complex and enigmatical appearances did not 
 present themselves, it would be a serious objection to the metamorphic 
 theory. 
 
 In the accompanying diagram I have represented carefully the lami- 
 
 * Geol. Quart. Journ. 1853, vol. ix. p. 172. 
 39 
 
610 
 
 LAMINATION OF " CLAY-SLATE." [Ca XXXVI 
 
 Lamiiuition of clay-slat, Montagne de Seguinat, 
 near Gavarnie, in the Pyrenees. 
 
 nation of a coarse argillaceous Fig. 709. 
 
 schist which I examined in 1830 
 in the Pyrenees. In part it ap- 
 proaches in character to a green 
 and blue roofing-slate, while part 
 is extremely quartzose, the whole 
 mass passing downwards into mi- 
 caceous schist. The vertical sec- 
 tion here exhibited is about 3 feet 
 in height, and the layers are 
 sometimes so thin that 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 laminee 
 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 move- 
 ment, and a similar process may account for what the quarry men 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 rnetamor- 
 phic 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 " primi- 
 tive." 
 
 * Bulletin Soc. Geol. de France, 2e s6r. vol. iv. p. 1301. 
 
CIT. XXXVII.1 AGE OF METAMORPHIC ROCKS. 611 
 
 CHAPTER XXXVH. 
 
 ON THE DIFFERENT AGES OF THE METAMORPHIC ROCKS. 
 
 Age of each set of metamorphic strata twofold Test of age by fossils and min- 
 eral character not available Test by superposition ambiguous Conversion 
 of dense masses of fossiliferoua 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 crys- 
 talline strata are very modern Order of succession in metamorphic rocks 
 Uniformity of mineral character Why the metamorphic strata are less cal- 
 careous than the fossiliferous. 
 
 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, espe- 
 cially 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. Accord- 
 ing 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-sohist, 
 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 vol- 
 canic or plutonic mass, and has been changed into marble or fc~- 
 
C12 AGE OF METAMOBPHIC EOCKS [Cn. XXXVil 
 
 schist, and another not far distant, where the same bed remains unaltered 
 and fossiliferous ; but when we have to compare two portions of a moun- 
 tain chain the one metamorphic, and the other unaltered all the labor 
 and skill of the most practised observers are required, and may sometimes 
 be at fault. I shall mention one or two examples of alteration on a grand 
 scale, in order to explain to the student the kind of reasoning by which 
 we are led to infer that dense masses of fossiliferous strata have been con- 
 verted into crystalline rock. 
 
 Northern Appenines Carrara. The celebrated marble of Carrara, 
 used in sculpture, was once regarded as a type of primitive limestone. 
 It abounds in the mountains of Massa Carrara, or the " Apuan Alps," 
 as they have been called, the highest peaks of which are nearly 6000 
 feet high. Its great antiquity was inferred from its mineral texture, 
 from the absence of fossils, and its passage downward 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 demonstrated that this marble, once supposed to be 
 formed before the existence of organic beings, is, in fact, an altered 
 limestone of the Oolitic period, and the underlying crystalline schists 
 are secondary sandstones and shales, modified by plutonic action. In 
 order to establish these conclusions it was first pointed out, that the cal- 
 careous 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 diorite, euphotide, serpentine, and granite, occurring in the same 
 country. 
 
 It was then observed that, in places where the secondary formations 
 are unaltered, the uppermost consist of common Apennine limestone 
 with nodules of flint, below which are shales, and at the base of all, ar- 
 gillaceous and siliceous sandstones. In the limestone, fossils are frequent, 
 but very rare in the underlying shale and sandstone. Then a gradation 
 was traced laterally from those 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 argilla- 
 ceous sandstones, are quartzite and gneiss.* Had these secondary strata 
 of the Apennines undergone universally as great an amount of transmu- 
 tation, it would have been impossible to form a conjecture respecting 
 their true age ; and then, according to the method of classification 
 adopted by the earlier geologists, they would have ranked as primary 
 
 * See notices of Savi, Hoffmann, and others, referred to by Boue, Bull, de la 
 Soc. Geol. de France, torn. v. p. 317; and torn, iii. p. xliv ; also Pilla, cited by 
 Murcbison, Quart. Geol. Journ. vol. v. p. 266. 
 
Cu. XXXVII] OF THE SWISS ALPS. 613 
 
 rocks. In that case the date of their origin would have been thrown back 
 to an area antecedent to .the deposition of the Lower Silurian or Cam- 
 brian 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 extended scale. 
 In the eastern part of that chain, some of the primary fossiliferous strata, 
 as well as the older secondary formations, together 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 second- 
 ary formations disappear, and the Cretaceous, Oolitic, Liassic, and at 
 some points even the Eocene strata, graduate insensibly into metamor- 
 phic 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 crystal- 
 line schist 
 
 It is difficult to convey to those who have never visited the Alps a 
 just idea of the various proofs which concur to produce this conviction. 
 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 granite. 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 num- 
 mulitie 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 second- 
 ary and even tertiary strata, which have assumed that semi-crystalline 
 texture which Werner called transition, and which naturally led his fol- 
 lowers, 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 plu- 
 tonic action which has entirely altered and rendered metamorphic so 
 many of the subjacent formations ; for in the Alps, this action has by 
 no means been confined to the immediate vicinity of granite. Granite, in- 
 deed, and other plutonic rocks, rarely make their appearance at the sur- 
 face, notwithstanding the deep ravines which lay open to view the 
 internal structure of these mountains. That they exist below at no 
 great depth we cannot doubt, and we have already seen (p. 569) that at 
 some points, as in the Valorsine, near Mont Blanc, granite and granitic 
 
614: AGE OF METAMOKPHIC ROCKS. [Cn. XXXVII 
 
 veins are observable, piercing through talcose gneiss, which passes insen- 
 sibly 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 formations of a comparatively 
 modern date, such as the Oolitic and Cretaceous, 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 complete alternations 
 on a large scale of secondary strata, containing fossils, with gneiss and 
 other rocks, of a perfectly metamorphic structure. I have visited some 
 of the most remarkable localities referred to by these authors ; but al- 
 though agreeing with them that there are passages from the fossiliferous . 
 to the metamorphic series far from the contact of granite or other plu- 
 tonic rocks, I was unable to convince myself that the distinct alterna- 
 tions of highly crystalline, with unaltered strata above alluded to, might 
 not admit of a different explanation. In one of the sections described 
 by M. Studer in the highest of the Bernese Alps, namely in the Roth- 
 thai, 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 ap 
 pearances 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 superposi 
 tion, 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 con- 
 vulsions have been on so stupendous a scale. 
 
 On the Sattel also, at the base of the 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 me- 
 chanical derangement. Almost any hypothesis of repeated changes of 
 position may be resorted to in a region of such extraordinary confusion. 
 The secondary strata may first have been vertical, and then certain por- 
 tions may have become metamorphic (the plutonic influence ascending 
 from below), while intervening strata remained unchanged. The whole 
 series of beds may then again have been thrown into a nearly horizontal 
 
CH. XXXVIL] ORDER OF SUCCESSION". 615 
 
 position, giving rise to the superposition of crystalline upon fossiliferous 
 formations. 
 
 It was remarked, in Chap. XXXTY., that as the hypogene rocks, both 
 stratified and unstratified, crystallize originally at a certain depth beneath 
 the surface, they must always, before they are upraised and exposed at 
 the surface, be of considerable antiquity, relatively to a large portion of 
 the fossiliferous and volcanic rocks. They may be fonning 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 format'on repose un- 
 conformably on gneiss, which was evidently crystalline befcre the deposi- 
 tion 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 tex- 
 ture has been superinduced in the Alps on Middle Eocene deposits (see 
 p. 600), we cannot doubt that, hereafter, geologists will succeed in de- 
 tecting crystalline schists of almost every age in the chronological series, 
 although the quantity of metamorphic rocks visible at the surface must, 
 for reasons above explained, diminish rapidly in proportion as the monu- 
 ments 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 par- 
 ticular 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 descending series, where 
 it is metamorphic, consists of, 1st, saccharine marble; 2dly, talcos> 
 schist; and 3dly, of quartz-rock and gneiss; where unaltered, of, 1st, 
 fossiliferous limestone ; 2dly, shale ; and 3dly, sandstone. , 
 
 But if we investigate different mountain chains, we find gneiss, mica- 
 schist, hornblende-schist, chlorite-schist, 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 crystalline 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 meta- 
 morphic order of rocks. It is probable that had they been subjected to 
 more intense plutonic action, they would have been transformed into 
 hornblende- schist, foliated chlorite-schist, scaly talcose-schist, mica-schist, 
 or other more perfectly crystalline rocks, such as are usually associated 
 with gneiss. 
 
616 SCARCITY OF LIME IN METAMORPHIC KOCKS. [OH. XXX Ylf, 
 
 Uniformity of mineral character in Hypogene rocks. Humboldt 
 has emphatically remarked, that when we pass to another hemisphere, 
 we see new forms of animals and plants, and even new constellations in 
 the heavens ; but in the rocks we still recognize our old acquaintances, 
 the same granite, the same gneiss, the same micaceous schist, quartz- 
 rock, and the rest. 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 min- 
 eral 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 uni- 
 form 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 hypogene 
 rocks, considered as aggregates of simple minerals, are really more homo- 
 geneous in their composition than the several members of the sediment- 
 ary 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 abun- 
 dant in the Grampians, are wanting in Cumberland, Wales, and Corn- 
 wall ; 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 plutonic 
 rocks of the Andes common felspar in those of Europe. In one part 
 of Scotland, 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 garnetif- 
 erous. And not only do the proportional quantities of felspar, quartz, 
 mica, hornblende, and other minerals, vary in hypogene rocks bearing 
 the same name ; but what is still more important, the ingredients, as 
 we have seen, of the same simple mineral are not always constant, 
 (p. 463 and table, p. 104). 
 
 The metamorphic strata, why less calcareous than the fossiliferous. 
 It has been remarked, that the quantity of calcareous matter in meta- 
 morphic 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 
 in exceedingly small proportion of interstratified calcareous beds, al- 
 though these have been the objects of careful search for economical 
 purposes. Yet limestone is not wanting in the Grampians, and it is 
 
CH. XXXVIL] SCARCITY OF LIME IN METAMORPHIC ROCKS. 617 
 
 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 crystalline 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 antece- 
 dently 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 volcanos, 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 carbo- 
 nate of lime. The quantity 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 cal- 
 careous rock chemically precipitated, and of many reefs of shelly and 
 coralline stone, must be derived from mineral matter subtracted by plu- 
 tonic 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 process, 
 fossil shells or corals may often lose their carbonic acid, and the resi- 
 dual lime may enter into the composition of augite, hornblende, garnet, 
 and other hypogene minerals. That the removal of the calcareous mat- 
 ter of fossil shells is of frequent occurrence, is proved by the fact of such 
 organic remains being often replaced by silex or other minerals, and 
 sometimes by the space once occupied by the fossil being left empty, or 
 only marked by a faint impression. We ought not indeed to marvel at 
 the general absence of organic remains from the crystalline strata, when 
 * See Principles, Index, " Calcareous Springs." 
 
618 MINERAL VEINS. [On. XXXVIII. 
 
 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 nietamorphic. Rocks of the last-mentioned 
 class, moreover, must have sometimes been exposed again and again to 
 renewed plutonic action. 
 
 CHAPTER XXXVIII. 
 
 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 Four- 
 net's observations in Auvergne Dimensions of veins Why some 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 vein in lias, Glamorganshire 
 Gold in Russia, California, and Australia Connection of hot springs and min- 
 eral veins Concluding remarks. 
 
 THE manner in which metallic substances are distributed through the 
 earth's crust, and more especially the phenomena of those nearly verti- 
 cal and tabular masses of ore called mineral veins, from which the larger 
 part of the precious metals used by man are obtained, these are sub- 
 jects 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 modi- 
 fied, 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 refera- 
 ble to one era, but are of various geological 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. Never- 
 theless, I have shown, when tracing in another work, the history and 
 progress of geology, that Werner was far behind some of his predeces- 
 sors in his theory of the volcanic rocks, and less enlightened than his 
 
CH. XXXYIIL] DIFFERENT KINDS OF MINERAL VEINS. 619 
 
 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 prime- 
 val or nascent condition of the planet; 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 de- 
 posits, and that dikes of porphyry, greenstone, and basalt, were fissures 
 filled with their several contents from above. Hence he naturally infer- 
 red 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 men- 
 struum," 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 enter- 
 tained 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 opera- 
 tions have been described and explained. 
 
 On different kinds of mineral veins. Every geologist is familiarly 
 acquainted with those veins of quartz which abound in hypogene strata, 
 forming lenticular masses of limited extent. They are sometimes ob- 
 served, also, in sandstones and shales. Veins of carbonate of lime are 
 equally common in fossiliferous rocks, especially in limestones. 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, calcareous, and occa- 
 sionally 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 irregu- 
 lar assemblage of veins, called by the Germans a " stockwerk," in allu- 
 sion 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. Metalliferous veins, referable to such 
 agency, are occasionally a few inches wide, but more commonly 3 or 4 
 
 * Principles, &c.. chap. iv. 
 
620 
 
 ORIGIN OF METALLIFEROUS VEINS. [Cn. XXXVIIL 
 
 feet. They hold their course continuously in a certain prevailing direc- 
 tion for miles or leagues, passing through rocks varying in mineral com- 
 position. 
 
 That metalliferous veins were fissures. As some intelligent miners, 
 after an attentive study of metalliferous veins, have been unable to re- 
 concile many of their characteristics with the hypothesis of fissures, I 
 j?i g . 7io. shall begin by stating the 
 
 evidence in its favour. The 
 most striking fact perhaps 
 which can be adduced in its 
 support is, the coincidence 
 of a considerable proportion 
 of mineral veins with faults, 
 or those dislocations 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. Thus, 
 for example, suppose a a, 
 fig. 710, to be a tin lode in 
 Cornwall, the term lode be- 
 ing applied to veins contain- 
 ing metallic ores. This 
 lode, running east and west, 
 is a yard wide, and is shift- 
 ed by a copper lode (b &), 
 of similar width. 
 
 The first fissure (a a) has 
 been filled with various ma- 
 terials, partly of chemical 
 origin, such as quartz, fluor- 
 spar, peroxide of tin, sul- 
 phuret of copper, arsenical 
 pyrites, bismuth, and sul- 
 phuret of nickel, and partly of mechanical origin, comprising clay and 
 angular fragments or detritus of the intersected rocks. The plates of 
 quartz and the ores are, in some places, parallel to the vertical sides or 
 walls of the vein, being divided from each other by alternating layers 
 of clay, or other earthy matter. Occasionally the metallic ores are dis- 
 seminated 'in detached masses among the vein-stones. 
 
 Vertical sections of the mine of Huel Peever, Redruth, 
 Cornwall. 
 
CH. XXXVIII.] ORIGIN OF METALLIFEROUS VEINS. 621 
 
 It is clear that, after the gradual introduction of the tin and other 
 substances, the second rent (b 1) was produced by another fracture ac- 
 companied by a displacement of the rocks along the plane of b b. This 
 new opening was then filled with minerals, some of them resembling 
 those in a a, as fluor-spar (or fluate of lime) and quartz ; others diffe- 
 rent, 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, de- 
 rived, probably, from the friction of the walls of the rent, or partly, 
 perhaps, washed in from above. This new movement has heaved the 
 rock in such a manner as to interrupt the continuity of the copper vein 
 (b b) } and, at the same time, to shift or heave laterally in the same di- 
 rection 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 repre- 
 sented 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, rf, c, , a, &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 Cornwall, that there are eight distinct systems of 
 veins which can in like manner be referred to as many successive move- 
 ments 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 
 imfrequently striated, or scored with parallel furrows and ridges, such as 
 would be produced by the continued rubbing together of surfaces of un- 
 equal hardness. These smoothed surfaces resemble the rocky floor over 
 which a glacier has passed (see fig. p. 127). They are common even in 
 cases wnere there has been no shift, and occur equally in non-metalliferous 
 fissures. They are called by miners " slicken-sides," from the German 
 scklichten, to plane, and seite, side. It is supposed that the lines of the 
 stria? indicate the direction in which the rocks were moved. During one 
 of the minor earthquakes in Chili, which happened about the year 1840 ? 
 and was described 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. 
 
 * GeoL Trans. voL iv. p. 139 ; Trans. Roy. GeoL Society, Cornwall, vol. ii. p. 90. 
 
622 SUCCESSIVE ENLAKGEMENTS OF VEINS. [Cn. XXXVIII. 
 
 When all movement had ceased, there were seen on the 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, contain- 
 ing 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 phenomena 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 occur- 
 rence in *hem 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.j- Marine fossil 
 shells, also, have been found at great depths, having probably been en- 
 gulfed during submarine earthquakes. Thus, a gryphaea is stated by 
 M. Virlet to have been met with in a lead-mine near Se"mur, in France 
 and a madrepore in a compact vein of cinnabar in Hungary .J 
 
 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 paral- 
 lelism 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 enlargements. 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 
 
 * Conyb. and Phil. Geol. p. 401 ; and Farey's Derbysh. p. 243. 
 f Carne, Trans, of Geol. Soc. Cornwall, vol. iii. p. 238. 
 j Fournet, Etudes sur les Depots Me"talliferes. 
 
CH. XXXVIIL] 
 
 ENLARGEMENTS OF VEINS. 
 
 623 
 
 minerals, arranged with the utmost regularity on each side of the cen- 
 tral layer. This layer was 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 precipi- 
 tates, 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 im- 
 pression 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 following curious and instructive example (fig. 713) 
 
 Fig. 713. 
 
 Copper lode, near Redruth, enlarged at six successive periods. 
 
 from a copper-mine in granite, near Redruth.* Each of the plates or 
 combs (a, b, c, d, e, /) 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 ham- 
 mer. 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 
 * Geol. Rep. on Cornwall, p. 340. 
 
624 SWELLING OUT OF VEINS. [Cn. XXXVIII. 
 
 with siliceous matter, as Von Buch observed, in Lancerote, the walls of 
 a volcanic crater formed in 1731 to be traversed by an open rent in 
 which hot vapours had deposited hydrate of silica, the incrustation 
 nearly extending to the middle.* Such a vein may then be filled with 
 clay or sand, and afterwards reopened, the new rent dividing the argil- 
 laceous deposit, and allowing a quantity of rubbish to fall down. Yarious 
 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 oc- 
 casional 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 superin- 
 tendence, 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, accom- 
 panied by sulphurets of iron and arsenical pyrites, was introduced. 
 Another convulsion then burst open the rocks along the old line of frac- 
 ture, 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 horn- 
 stone 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 catas- 
 trophes may be the monuments, not of one paroxysmal shock, but of 
 reiterated movements. 
 
 Such repeated enlargement and reopening 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 any where 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 considerable pressure. Trappean dikes 
 can rarely fail to strengthen the rocks at the points where before they 
 were weakest ; and if the upheaving 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. 
 
 * Principles, ch. xxvii 8th ed. p. 422. 
 
Cs. XXXVIIL] SWELLING OUT OF VEINS. 625 
 
 A large proportion of metalliferous veins have Uieir opposite walls 
 nearly parallel, and sometimes over a wide extent of country. There 
 is a fine example of this in the celebrated vein of Andreasburg in the 
 Hartz, which has been worked for a depth of 500 yards perpendicularly, 
 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 one or two inches in one part, and then 8 or 10 feet in an- 
 other, 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 different mineral composition. 
 If, therefore, the opposite 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. T14. 
 
 Fig. 715. 
 
 
 ^ - ? 
 
 _ B i'V 
 
 cf- a> 
 
 ^d^ 
 
 Fig. 716. 
 
 
 Let a b, fig. 714, be a line of fracture traversing a rock, and let a bf 
 fig. 715, represent the same line. Now, if we cut a piece of paper re- 
 presenting 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 insolated cavities at d d d, and when we compare such figures 
 with nature we find that, with certain modifications, they represent the 
 interior of faults and mineral veins. If, instead of sliding the cut paper 
 to the right hand, we move the lower part towards the left, about the 
 same distance that it was previously slid to the right, we obtain consid- 
 erable variation in the cavities so produced, two long irregular open spa- 
 ces, //, fig. 7 1 6, being then formed. This will serve to show to what slight 
 circumstances 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 frequent- 
 ly very straight ; but if tortuous, it is found to be choked up with clay, 
 
 40 
 
626 CHEMICAL DEPOSITS IN VEINS. [Ca XXXVIII 
 
 stones, and pebbles, at points where it departs most widely Fig. 7i". 
 from vertically. Hence at places, such as a, fig. 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 sub- 
 stances 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 production 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 earth- 
 quakes, 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 plu- 
 tonic and stratified formations, especially where the former sends veins 
 into the latter, a circumstance which indicates an original proximity of 
 veins at their inferior extremity to igneous and heated rocks. It is more- 
 over acknowledged that even those mineral and thermal springs, which, 
 in the present state of the globe, are far from volcanos, are nevertheless 
 observed to burst out along great lines of upheaval and dislocation of 
 rocks.* It is also ascertained that all the substances with which hot 
 springs are impregnated agree with those discharged in a gaseous form 
 volcanos. Many of these bodies occur as veinstones ; such as silex, 
 carbonate of lime, sulphur, fluor-spar, sulphate of barytes, magnesia, 
 oxide of iron, and others. I may add that, if veins have been filled 
 with gaseous emanations from masses of melted matter, slowly cooling in 
 the subterranean regions, the contraction of such masses as they pass 
 from a plastic to a solid state would, according to the experiments of 
 Deville on granite (a rock which may be taken as a standard), produce 
 a reduction in volume amounting to 10 per cent. The slow crystalliza- 
 tion, 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 
 
 * See Dr. Daubeny's Volcanos. 
 
Cn. XXXVIII.] CHEMICAL DEPOSITS IX VEIXS. 627 
 
 has often been an intimate connection between metalliferous veins and 
 hot springs holding mineral matter in solution, yet v?e must not on 
 that account expect that the contents of hot springs and mineral veins 
 would be identical. On the contrary, M. E. de Beaumont has judi- 
 ciously 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 ave- 
 rage 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 compo- 
 sition 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 temporature, 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?\ 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 originally on the sulphurets and muriates of copper, tin, 
 iron, and zinc, dissolved in the hot water of fissures, so as to deter- 
 mine the peculiar mode of their distribution. After instituting experi- 
 ments on this subject, he even endeavored to account for the preva- 
 lence of an east and west direction in the principal Cornish lodes by 
 their position at right angles to the earth's magnetism ; but Mr. Hen- 
 wood and other experienced miners have pointed out objections to 
 
 * Bulletin, iv. p. 1278. f R. TV. Fox on Mineral Veins, p. 10. 
 
628 RELATIVE AGE OF METALS. [Ca. XXXVIIL 
 
 the theory ; and it must be owned that the direction of veins in different 
 mining districts varies so entirely that it seems to depend on lines of 
 fracture, rather than on the laws of voltaic electricity. Nevertheless, as 
 different kinds of rock would be often in different electrical conditions, 
 we may readily believe that electricity must often govern the arrange- 
 ment of metallic precipitates in a rent. 
 
 " I have observed," says Mr. R Fox, " that when chloride of tin in 
 solution is placed in the voltaic circuit, part of the tin is deposited 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 experi- 
 ment may serve to explain why tin is found contiguous to, and inter- 
 mixed .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 eruptions 
 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 Grent Britain. The government survey of Ireland has demonstrated, 
 that in Wexford veins of copper and lead (the latter as usual being 
 argentiferous) are much older than the tin of Cornwall. In each of the 
 two countries a very similar series of geological changes has occurred at 
 two distinct epochs, in Wexford, before the Devoniam 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 Devoniam 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 certainly posterior 
 to the Silurian, and anterior to the Devonian ; for they do not enter 
 .the lalter, and, what is still more decisive, streaks or layers of 
 
 * E. W. Fox on Mineral Veins, p. 38. 
 
CH. XXXVIII] RELATIVE AGE OF METALS. 629 
 
 derivative copper have been found near Wexford in the Devonian, 
 not far from points where mines of copper are worked in the Silurian 
 strata.* 
 
 Although the precise age of such copper lodes cannot be defined, we 
 may safely affirm that they were either filled at the close of the Silurian 
 or commencement of the Devonian period. Besides copper, lead, and 
 silver, there is some gold in these ancient or 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. 569.), 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. 621. 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 pro- 
 bably 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 con- 
 taining olivine, which overlies tertiary lignite, in which are leaves of 
 dicotyledonous trees. This silver, therefore, is decidedly a tertiary for- 
 mation. In regard to the age of the gold of the Ural Mountains, in 
 Russia, which, like that of California, is obtained chiefly from auriferous 
 alluvium, it occurs in veins of quartz in the schistose and granitic rocks 
 of that chain, and is supposed by MM. Murchison, De Verneuil, and Key- 
 serling to be newer than the syenitic granite of the Ural perhaps of ter- 
 tiary date. They observe, that no gold has yet been found in the Per- 
 
 * I am indebted to Sir H. de la Beche for this information. See also mapa 
 and sections of Irish Survey. 
 
 f Sir H. de la Beche, MS. notes on Irish Survey, 
 j Report on Geology of Cornwall, p. 310. 
 
630 GOLD OF AUSTRALIA. [Cn. XXXVIII. 
 
 mian 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 mam- 
 moth being common in the gravel at the foot of the Ural Mountains, 
 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 formations, so called be- 
 cause 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 rnetarnorphic Silurian strata, as well as in auriferous gravel de- 
 rived from the same. v 
 
 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 shoiX distances from the veins. In Australia 
 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 longi- 
 tude, and yields already an annual supply equal, if not superior, to that 
 of California ; nor is there any apparent prospect of this supply diminish- 
 ing, still less of the exhaustion 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 experi- 
 enced 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, t for the most part, to rocks older than those bearing 
 lead. The tin veins will be of higher relative antiquity for the same 
 reason that the "underlying" igneous formations or granites which 
 are visible to man are older, on the whole, than the overlying or trap- 
 pean 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 EEMARKS. 631 
 
 metals, it will follow that those formed farthest from the surface will 
 usually require the longest time before they can be exposed superficially. 
 In order to bring them into view, or within reach of the miner, a greater 
 amount of upheaval and denudation must take place in proportion as 
 they have lain deeper when first mowed. A considerable series of geo- 
 logical 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 favor. 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 particular periods 
 It has also sprung, in some degree, from extrinsic considerations; many 
 geologists having been unwilling to believe the doctrine of the transmu- 
 tation 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, conse- 
 quently, 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 and vegetable life has been sustained. 
 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 admirably fitted for the new states of 
 the globe as they arose, or they would not have increased and multiplied 
 and endured for indefinite periods.* 
 
632 CONCLUDING- REMARKS. [Cfl. XXXVIII 
 
 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 demonstrated 
 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 infinite wisdom and power 
 which it displays, our admiration is multiplied 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. 
 
 f See the author's Anniv. Address to the Geol, Soc. 1837. Proceedings G. 8. 
 vol. ii. p. 620. 
 
SUPPLEMENT 
 
 LONDON, APRIL 25, 1857. 
 
SUPPLEMENT 
 
 BRITISH PLIOCENE STRATA. 
 
 British Pliocene Strata Proofs from fossil shells of a gradual refrigeration of 
 climate in England, at the successive periods of the Coralline, the Bed, and 
 the Norwich Crag Searles "Wood's Monograph on the Crag Mollusca. The 
 Crag Mastodon, a Pliocene species Different assemblages of fossil Mammalia 
 in the freshwater and drift deposits of the Valley of the Thames Fossil 
 Musk-buffalo in the drift near London and near Berlin. 
 
 SINCE the appearance of the fifth edition of this work, Mr. Searles 
 Wood has brought to a conclusion his important Monograph on the 
 Crag and Upper Tertiary shells of Britain.* The results of his con- 
 scientious examination of so many hundred species of testacea, in so 
 far as they bear on Geology, will be found to agree with the classifica- 
 tion adopted in the text (pp. 152 165, &c.), especially as relates to 
 the position of the several divisions of the Crag in the great European 
 series of formations. But we may also deduce from the same Mono- 
 graph clear evidence of a gradual refrigeration of climate, which went 
 on in the area of England from the time of the older to that of the most 
 modern Pliocene strata, a refrigeration which was inferred from the 
 Crag shells in 1846, by the late Edward Forbes.f No analysis of this 
 excellent treatise has been drawn up for us by Mr. Wood himself: we 
 have therefore inserted the following tables, to point out many general 
 conclusions to which the conchological data seem to lead. In drawing 
 them up I have had the able assistance of Mr. S. P. Woodward, the 
 well-known author of the "Manual of the Mollusca, Recent and 
 Fossil."! 
 
 Number of known Species of Marine Testacea in the three English 
 Pliocene Deposits, called the Norwich, the Red, and the Coralline 
 Crags. 
 
 Brachiopoda G 
 
 Conchifera - - - - 206 
 
 Gasteropoda .... 230 
 
 Total- - - - 442 
 
 6 Paleontographical Society, 1848 to 1856. 
 
 f Mem. of Geol. Survey, London, 1846, p. 391. 
 
 J London: 1853-6. 
 
636 BRITISH PLIOCENE STRATA. 
 
 Distribution of the above Marine Testacea. 
 
 Number of Species. Species common to the 
 
 Norwich Crag 81 
 
 Red Crag - - - -225 
 
 Coralline Crag - - - 327 
 
 Norwich and Red Crag (not in Cor.) 33 
 Norwich and Coralline (not in Red) 4 
 Red and Coralline (not in Norwich) 116 
 Norwich, Red, and Coralline - 19* 
 
 Proportion of Recent to Extinct Species. 
 
 Percentage of 
 Recent Extinct Eecent 
 
 Norwich Crag .... 69 12 85 
 
 Red Crag 130 95 57 
 
 Coralline Crag - - - - 168 159 51 
 
 Recent Species not living now in British Seas. 
 
 Northern Species. Southern. 
 
 Norwich Crag - 12 
 
 Red Crag .... 8 16 
 
 Coralline Crag ... 2 27 
 
 lu the above list I have not concluded the shells of the glacial beds 
 of the Clyde and of several other British deposits of newer origin than 
 the Norwich Crag, in which nearly all perhaps all the species are 
 recent, although such fossils are described by Mr. Wood, or enumer- 
 ated in his Appendix. The land and freshwater shells, 32 in number, 
 have also been purposely omitted, as well as three species of London 
 Clay shells, suspected by Mr. Wood himself to be spurious. 
 
 By far the greater number of the recent marine species included in 
 these tables are still inhabitants of the British seas ; but even these dif- 
 fer considerably in their relative abundance, some of the commonest of 
 the Crag shells being now extremely scarce ; as, for example, JBuccinum 
 Dalei, and others, rarely met with in a fossil state, being now very com- 
 mon, as Murex erinaceus and Cardium echinatum. 
 
 The last table throws light on a marked alteration in the climate of 
 the three successive periods. It will be seen that in the Coralline Crag, 
 there are 27 Southern shells, including 26 Mediterranean, and one 
 West Indian species (Erato Maugerce). Of these only 13 occur in the 
 Red Crag, associated with 3 new Southern species, while the whole of 
 them disappear from the Norwich beds. On the other hand, the Coral- 
 line Crag contains only 2 Arctic shells, Admete viridula and Limopsis 
 pygmcea ; whereas the Red Crag contains, as stated in the table, 8 
 Northern species, all of which recur in the Norwich Crag, with the 
 addition of 4 others, also inhabitants of the Arctic regions ; so that 
 there is good evidence of a continual refrigeration of climate during 
 the Pliocene period in Britain. The presence of these Northern shells 
 cannot be explained away by supposing that they were inhabitants of 
 the deep parts of the Sea ; for some of them, such as Tellina calcarea 
 and Astarte borealis, occur plentifully, and sometimes with the valves 
 
 These 19 species must be added to the numbers 33-4 and 116 respectively, 
 in order to obtain the full amount of common species in each of those cases. 
 
MASTODON OF NORWICH CRAG. 637 
 
 united by their ligament, in company with other littoral shells, such as 
 Mya arenaria and Littorina rudis, and evidently not thrown up from 
 deep water. Yet the northern character of the Norwich Crag is not 
 fully shown by simply saying that it contains 12 Northern species now 
 no longer found in British seas, since several boreal shells which still 
 linger in the Scottish deeps do not abound there as they did in the lat- 
 ter days of the Crag Period. It is the predominance of certain genera 
 and species which satisfies the mind of a conchologist as to the Arctic 
 character of the Norwich Crag. In like manner, it is the presence of 
 such genera as Pyrula, Columbella, Terebra, Cassidaria, Pholadomya^ 
 Lingula, Discina, and others, which give a southern aspect to the Coral- 
 line Crag shells. 
 
 In conclusion, it may be observed that the cold which had gone on 
 increasing from the time of the Coralline to that of the Norwich Crag 
 continued, though not perhaps without some oscillations of temperature, 
 to become more and more severe after the accumulation of the latter, 
 until it reached its maximum in what has been called the Glacial epoch. 
 The marine fauna of this last period contains, both in Ireland and Scot- 
 land, recent species of mollusea now living in Greenland and other seas 
 far north of the areas where we find their remains in a fossil state. 
 
 It is not in reference to the two older formations above alluded to, 
 but when we attempt to classify the lacustrine and fluviatile deposits 
 (some contemporaneous with the marine Norwich Crag and others pos- 
 terior to it), that we encounter in the East and South of England the 
 greatest difficulty. When treating of the Newer Pliocene and drift 
 formation in the Valley of the Thames, I have acknowledged the per- 
 plexity in which this subject is still involved, and have hinted at the 
 causes of it (chap. xiii. pp. 152, 153). Every year, however, removes 
 some of this ambiguity ; for the true relative position of distinct sets of 
 superficial strata becomes more clearly understood, and the specific 
 characters of the fossil mammalia and shells better ascertained. In the 
 first place, the occurrence in the Norwich Crag of many marine shells 
 of Northern species, as before described, in company with land and 
 freshwater shells, and some mammalia of a more Southern character, 
 may possibly be explained by supposing the sea of the Norwich Crag 
 to have been opened towards the Pole, with islands interspersed, while 
 the land of the same period was continuous far to the South. In that 
 direction a Continent may have existed, from which rivers flowed north- 
 wards, in whose waters the hippopotamus and such shells as the Cyrena 
 consobrina flourished. 
 
 The Mastodon found in the Red and Norwich Crag (p. 155, and fig. 
 135, p. 165) was till lately regarded as a Miocene or Falunian species; 
 and under this persuasion, calling it M. angustidens, on the authority of 
 Professor Owen, I suggested that its remains might have been washed 
 out of older strata into the Crag, just as we sometimes observe London 
 Clay and Chalk fossils occasionally introduced into the same deposit. 
 Many teeth of this Mastodon, together with numerous ear-bones of 
 
638 FOSSIL MAMMALIA IN MODERN 
 
 whales, have recently been found at Felixstow, in what is called " the 
 detrital bed," so rich in phosphate of lime used in agriculture. That 
 accumulation of drifted materials lies at the base of the Red Crag, and 
 it has been supposed that the imbedded mammalian fossils were derived 
 from the destruction of an older set of strata. But in regard to the 
 Mastodon above mentioned, Dr. Falconer, who has devoted fifteen years 
 to the study of the fossil and recent Proboscideans, assures me that the 
 fossil is a well-known Pliocene animal, first observed in Auvergne by 
 MM. Croizet and Jobert, and called by them Mastodon arvernensis. 
 Cuvier did not adopt this name, for he had seen but a few specimens 
 from Auvergne, and he confounded it with M. angustidens. The entire 
 skeleton of both these Mastodons having now been obtained, they are 
 found to be referable to two distinct sub-genera. The Crag fossil be- 
 longs to the Tetralophodon of Falconer, a sub-genus of which five spe- 
 cies are known, so called because there are four ridges in the penulti- 
 mate true molar as well as in the two teeth which are placed immedi- 
 ately before it in both jaws. The Mastodon angustidens, on the other 
 hand, belongs, with six other species, to the section called Trilophodon, 
 in which the corresponding teeth have each three ridges. This Masto- 
 don, according to MM. Lartet and Falconer, is characteristic of the 
 Faluns and of the Molasse at Sansan at the foot of the Pyrenees, and 
 of several other Miocene localities.* 
 
 The Mastodon arvernensis is, according to Dr. Falconer, the only one 
 yet found in England. It abound^ with the Hippopotamus major in 
 the Pliocene strata of the Val d'Arno, as well as in strata of the same 
 age in Piedmont and at Montpellier. It may be considered, therefore, 
 as a characteristic Pliocene species ; and this view is in accordance with 
 the fact that its remains are best preserved in freshwater strata, asso- 
 ciated and coeval with the Norwich Crag. But we have no evidence of 
 its surviving in England till the still more modern epoch of those flu- 
 viatile deposits in the valley of the Thames in which the Hippopotamus 
 major and a species of monkey, Macacus plioccenus, have been detected. 
 These freshwater strata are alluded to in the text (p. 153), as occurring at 
 Grays in Essex, 21 miles below London, and at Ilford, Erith, and other 
 places bordering the Thames. They consist of sand, gravel, and loam, 
 from 60 to 100 feet thick, and often form a terrace on each side of the 
 valley, rising to a much higher level than a vast bed of more modern 
 gravel, to which allusion will presently be made. At Grays, the Cyrena 
 consobrina of the Nile already mentioned, a shell common to the Nor- 
 wich Crag, together with several other shells no longer inhabitants of 
 Great Britain, and some of them unknown as living in any part of the 
 globe, occur, mingled with a vast majority of English species of land 
 and freshwater mollusca. The Cyrena, which I supposed till lately to 
 
 Professor Owen has given (Quart. Geol. Jour., Feb. 1856, p. 223), as a 
 synonym of the Crag Mastodon, the name of M. longirostris, Kaup, a fossil of 
 the Miocene sands of Eppelsheim, referred by Falconer to the sub-genus Tetralo- 
 phodon. 
 
DEPOSITS OF THAMES VALLEY. 639 
 
 be a genus unknown in Europe (p. 153), is, as I learn from Mr. Wood- 
 ward, a living Sicilian shell, called by some naturalists C. panormitana. 
 With these fossils, and with the Hippopotamus and monkey above 
 alluded to, the remains of Rhinoceros leptorhinus are found ; while the 
 accompanying elephant is not the Mammoth, as formerly imagined, 
 but, according to Dr. Falconer, Elephas antiquus, and sometimes E. 
 priscus. 
 
 It is still a matter of discussion whether the submergence of a great 
 part of the Southeast of England beneath the sea of the glacial epoch, 
 during which the Northern erratics of Norfolk and Suffolk, and of 
 Highgate Hill, near London, were drifted southwards by ice, took place 
 before or after the origin of these deposits at Grays, Ilford, and other 
 places on the banks of the Thames ; but it is quite clear that after those 
 fluviatile beds were formed, a great sheet of ochreous gravel was spread 
 out over the lower levels of the same valley, and in it we find buried 
 the remains of Arctic quadrupeds. This ochreous gravel extends from 
 East to West, from above Maidenhead, through London, to the sea, for 
 a distance of 50 miles, having a width varying from 2 to 9 miles, and 
 a thickness of from 5 to 15 feet.* In many places it contains the bones 
 and teeth of the Siberian Mammoth (E. primigenius) and Siberian 
 Rhinoceros (R. tichorhinus), together with remains of the reindeer, 
 horse, and other quadrupeds. 
 
 Recently (1855) three fossil skulls, referred by Prof. Owen to the 
 Musk-buffalo (Bubalus moschatus), a well-known living inhabitant of 
 Arctic regions, have also been discovered ; one of them in the valley of 
 the Thames at Maidenhead, and the other two in gravel of the same 
 age near Batheaston, in the valley of the Avon. 
 
 The same musk-buffalo was met with about 20 years ago in the sub- 
 urbs of Berlin, in the hill called the Kreuzberg, imbedded in northern 
 drift, and with it the Siberian Elephant and Rhinoceros, together with 
 species of horse, deer, and ox.f 
 
 Among the fossil mammalia of another locality in the same drift of 
 North Germany, Dr. Hensel, of Berlin, has detected, near Quedlinburg, 
 the Norwegian Lemming, Myodes lemmus, and another species of the 
 same family called by Pallas Myodes torquatus (by Hensel Misother- 
 mus torquatus), a still more Arctic quadruped found by Parry in lati- 
 tude 82, and which never strays farther south than the northern borders 
 of the woody region. Professor Beyrich also informs me that the 
 remains of the Rhinoceros tichorhinus were obtained at the same place.J 
 In this " diluvium," as it is termed by many, no instance has as yet 
 
 Prestwich ; Geol. Quart. Joum., vol. xii. p. 131. 
 
 f I was shown in the Berlin Museum, in 1856, part of the skull of the Buba- 
 lus moschatus, correctly named in the catalogue of the Museum for 1837, the year 
 after its discovery, by Professor Quenstedt, at that time curator. The associated 
 Kreuzberg fossils are enumerated in Leonhard and Bronn's Jahrbuch, 1836, 
 p. 215. 
 
 % Zeitschrift der Deutsch. Geol. Gesellschaft, vol. vii. (1855), p. 548, &c. 
 
640 CLASSIFICATION OF MIOCENE 
 
 occurred in North Germany of the association of the Hippopotamus, or 
 any genus which would indicate a climate too warm for the reindeer, 
 musk-ox, or lemming ; so that it becomes more and more probable that 
 the alleged association of the Mammoth (E. primigenius), in the valley 
 of the Thames, with the hippopotamus and monkey (Macacus plioccenus), 
 and a like mixture of the bones and teeth of the tichorhine and lepto- 
 rhine rhinoceroses in the cliffs of Norfolk, may have arisen from con- 
 founding together the fossils of different deposits and periods, or from 
 an intermixture, due to natural causes, of the fossil remains of more than 
 one epoch. 
 
 Professor Owen remarks, that as the musk-buffalo has a constitution 
 fitting it at present to inhabit the high northern regions of America, 
 we can hardly doubt that its former companions, the warmly-clad Mam- 
 moth and the two-horned woolly rhinoceros (1$. tichorhinus), were in 
 like manner capable of supporting life in a cold climate.* 
 
 To what part of the Pliocene Period the Cave animals of Great 
 Britain should be chiefly referred, is still a vexed question. There 
 seems, however, no reason at present to suppose any of them more an- 
 cient than the Norwich Crag ; and many caves may have remained 
 open during the glacial and post-glacial eras, while the fauna was grad- 
 ually changing, so that the remains found in them may not always be- 
 long to strictly contemporary quadrupeds. 
 
 I have mentioned (p. 175) the occurrence in the suburbs of Rome of 
 the remains of Elephants, and referred them to E. primigenius ; but, 
 according to Dr. Falconer, there is no well-authenticated example of this 
 species having ever been met with South of the Alps. The specimens 
 from Monte Mario, and other localities near Rome, belong, according to 
 him, to E. antiquus, Falc., and E. meridionalis, Nesti, and those in 
 Piedmont and Lombardy to the same species, together with Elephas 
 prisons. 
 
 WHERE TO DRAW THE LINE BETWEEN THE MIOCENE AND EOCENE 
 TERTIARY STRATA, pp. 115, 175, 183. 
 
 Classification of the Miocene and Eocene strata Where to draw the line be- 
 tween Upper Eocene and Lower Miocene Reasons for a proposed change of 
 nomenclature Miocene fossil shells and quadrupeds of the Sewalik or Sub- 
 Himalayan hills. 
 
 I HAVE stated in the fifteenth chapter (p. 183), that many eminent 
 geologists consider the Marine Sands of the Forest of Fontainebleau, to- 
 gether with their equivalents in age in Belgium, Germany, and else- 
 where, as the base of the Miocene division of the great Tertiary series. 
 
 Geol. Quart. Journ., vol. xii. p. 124. 
 
AND EOCENE STRATA. 641 
 
 Accordingly, I have introduced in the table, at p. 105, the name of 
 " Lower Miocene" as a synonym much in vogue on the Continent for 
 strata of that age, called by me " Upper Eocene." It is unnecessary to 
 repeat the reasons so fully set forth in the text, which induced the late 
 Professor E. Forbes and me to employ this arrangement and nomencla- 
 ture in preference to one which throws into the same division the fatuns 
 of Touraine (originally selected by me as the type of the Miocene) and 
 a fauna so distinct as that of the Fontainebleau Sands, which contains 
 no species of shells in common with the "faluns," and which approaches 
 so nearly in the general character of its fossils to the typical Eocene 
 fauna. I observed, however (pp. 186, 187), that I was not unprepared 
 for the necessity of including hereafter the deposits above alluded to in 
 one and the same Miocene Period, should sufficient evidence be brought 
 to light of intermediate and connecting links between the Fontainebleau 
 sands or Limburg beds 'and the faluns of Touraine. 
 
 In the course of the last two years some progress has certainly been 
 made in bridging over the wide gulf which formerly separated the so- 
 called *' Lower Miocene" from the " faluns," while on the other hand 
 the Eocene system is becoming so comprehensive and so complicated in 
 its details by the continual intercalation of new formations, and by the 
 addition below its former base of the Thanet sands and Lower Lande- 
 nian of Belgium, that the desirability of limiting its extension in an up- 
 ward direction is becoming more and more obvious. The Thanet Sands, 
 moreover, exhibit a testaceous fauna, almost as divergent from that of 
 the Barton clay as are the shells of the Fontainebleau Sands from those 
 of the faluns ; so that, if we comprise the Thanet and Barton beds in 
 one Eocene Period, we may be called upon, with almost equal pro- 
 priety, to class the Fontainebleau and Falunian faunas in one and the 
 same great Miocene system. 
 
 Professor Beyrich, in a recently published memoir on the tertiary 
 strata of the North of Germany,* has made known to us the existence 
 of a long succession of marine strata, leading almost gradually from 
 the equivalents of the Lowest Limburg or Tongrian beds of Dumont to 
 others approaching in age the faluns of the Loire. Consequently he 
 has thought fit to introduce a new term that of " Oligocene " for all 
 the beds intermediate between Eocene and Miocene ; and, having dis- 
 tributed the strata in question into seven subdivisions, each character- 
 ized by a certain proportion of peculiar fossils, he refers the uppermost 
 of all, or his Sternberg beds, to the " Upper Oligocene ;" the next five, 
 comprising among others the Upper and Middle Limburg, to the " Mid- 
 dle Oligocene ;" and the remaining two to the Lower Oligocene, com- 
 prehending the Lower Tongrian of Dumont with the Brown-coal of 
 Germany, which is classed as the lowest of all. 
 
 M. Alcide d'Orbigny had previously (1852), in his Paleontology, con- 
 sidered all these " Oligocene " beds as a Lower Falunian division, class- 
 ing the faluns of the Loire as LTpper Falunian. Dr. Sandbcrger, in his 
 
 Abhandlungen der Konigl. Acad. der Wissen. zu Berlin, 1855. 
 41 
 
64:2 CLASSIFICATION OF MIOCENE 
 
 writings on the fossils of the Mayence Basin, has lately pointed out 
 several connecting links between the beds commonly called Lower 
 Miocene and the overlying formations coeval with the faluns of Tou- 
 raine. M. Raulin, also, in a paper just printed on the faluns of the Gi- 
 ronde,* has given the names of Middle and Lower Miocene to the 
 equivalents of the Fontainebleau and Limburg beds, or to Professor 
 Beyrich's " Oligocene'' strata, the faluns of Touraine being classed as 
 " Upper Miocene." 
 
 M. Hebert published, in 1855, a map descriptive of the areas of two 
 tertiary seas, which succeeded each other in the Paris Basin, the first 
 that of the Calcaire grossier, and the second, that of the Fontaiuebleau 
 Sands, showing how marked is the want of coincidence between them 
 a fact which implies the occurrence of great geographical changes in 
 the interval of time between the two eras compared. In the explana- 
 tion of his map he gives his reasons for regarding the zone of Cerithium 
 plicatum, or that of the Fontainebleau Sands, as the most convenient 
 line of demarcation between Lower and Middle tertiary, or between 
 Eocene and Miocene.f M. Lartet, also a distinguished French osteolo- 
 gist, whose writings on fossil mammalia are so well known, has favored 
 me with his valuable counsel on this controverted subject ; observing, 
 that although the fossil testacea of the Fontainebleau Sands show a 
 preponderance of affinities towards an Eocene fauna, and small connec- 
 tion with the faluns of Touraine, yet, on the other hand, the freshwater 
 "Calcaire de la Beauce," immediately overlying the Fontainebleau 
 Sands, and other lacustrine formations in Auvergne and Central France, 
 as well as the Mayence Basin, cannot be included- in the same Eocene 
 system without doing violence to paleontological principles. The group- 
 ing of the fossil mammalia, he remarks, becomes less natural by such an 
 arrangement; for not only many genera, but even some species, are 
 found on both sides of the arbitrary line of demarcation thus drawn 
 between Eocene and Miocene. The genera Dorcatherium, Cainotherium, 
 Anchitherium, and Titanomys, for example, and Rhinoceros incisivus 
 and others, are made common to Eocene and Miocene. 
 
 Professor Forbes, in his posthumous memoir on a tertiary formation 
 of fluvio-marine origin in the Isle of Wight, J has observed, that there 
 are certain bands of well-marked fossils so widely extended as to indi- 
 cate definite horizons ; and of these perhaps the most constant is " the 
 zone of Cerithium plicatum" well-marked among the Tertiaries of 
 France, Belgium, and Germany, and equally so in the Isle of Wight. 
 Referring then to the connection between this zone and the underlying 
 formations, he continues : " There is evidently no break in this part of 
 the series of Tertiary depositions, and it would be harsh and forced to 
 place one portion in the Eocene, and another in the Miocene, as has 
 been done by continental geologists. In the Isle of Wight we have 
 
 Actes de 1' Academic de Bordeaux, 1855. 
 
 f Bulletin, 1855, torn. xii. p. 760. 
 
 J Mem. Geol. Survey, London, 1856, p. 99. 
 
AND EOCENE STRATA. 643 
 
 the true clue to their relation clearly exhibited in unmistakable and 
 perfect sections ; the importance of which clue in its bearing on conti- 
 nental geology may be estimated very highly." 
 
 The opinion of my late lamented friend, so emphatically expressed 
 in this passage in favor of the classification which I formerly adopted, 
 will convince every reader that the old nomenclature might be defended 
 by many cogent arguments ; and some of these M. Deshayes has lately 
 set forth in the preliminary chapter of his supplement to " The Fossil 
 Shells of the Paris Basin;"* where he says, that while, on the one 
 hand, the dissimilarity is enormous between the fossils of the Fontaine- 
 bleau Sands and those of the faluns of the Loire, we find the fauna of 
 the former to be allied to that of the marine beds below the Paris gyp- 
 sum by a predominance of certain genera of shells. These he enumer- 
 ates, and his observations are in harmony with what I have said (p. 
 184) respecting the "Eocene aspect" of the testaceous fauna of those 
 strata which occupy the debatable ground. 
 
 Notwithstanding these and many other arguments which might be 
 adduced in support of the classification formerly advocated by me, and 
 given in my Table at pp. 104-5, I have come to the conclusion that it 
 will be more convenient to draw the line of separation in the pla<3e so 
 generally adopted in France, provided that we always regard it as an 
 arbitrary and purely conventional line, one which has no pretensions 
 to be founded on any great change of species, still less on any general 
 revolution in the earth's physical geography assumed to have happened 
 at the era referred to. The classification was originally suggested in 
 France by an accidental break in the regular succession of marine 
 strata, caused by the intercalation on the site of Paris of certain fresh- 
 water gypseous marls, in which the Paleothere and other quadrupeds 
 were discovered. By these marls the marine sands of Beauchamp, often 
 called the "Sables Moyens," were separated from the marine sands of 
 Fontainebleau. In countries where no such interruption occurs, the 
 series, whether composed of freshwater, fluvio-marine, or marine strata, 
 will exhibit " beds of passage" between Eocene and Miocene, such as 
 those of Hempstead, in the Isle of Wight, or those recently discovered 
 in the Alps by MM. Hebert and Renevier, and described by them in the 
 Bulletin of the Statistical Society of the Department of the Seine 
 (1854). In this interesting memoir an account is given of a formation 
 termed by the authors " the Upper Nummulitic," which occurs in the 
 neighborhood of Gap, and in the Diablerets in Savoy, where the Ceri- 
 thium plicatum and other shells usually accompanying it in the Fon- 
 tainebleau Sands and in Belgium are abundantly intermixed with spe- 
 cies frequent in the Gres de Beauchamp, and even in the inferior Cal- 
 caire Grossier. Here, therefore, we have an example, among, the 
 highly elevated and contorted strata of the Alps, of marine beds of pas- 
 sage of the period under consideration, remarkable for many reasons, 
 
 Description des Animaux sans Vertebras, &c. Paris, 1857, p. 17. 
 
644 
 
 CLASSIFICATION OF MIOCENE STRATA. 
 
 and, among others, for the profusion of nummulites in association with 
 shells characteristic of the Fontainebleau Sands. This association has 
 obliterated one of the supposed distinguishing characters of the beds 
 above and below the gypseous series, for nummulites have never been 
 traced in Belgium, French Flanders, England, or Germany, above the 
 zone of Cerithium plicatum, or if so, in extremely small numbers, and 
 as exceptional cases. It was also thought by many geologists that the 
 principal upheaval or disturbing movements of the Alps occurred ex- 
 actly between the Lower and Middle Tertiary, or between the Eocene 
 and Miocene epochs, as usually defined in France, whereas the plentiful 
 occurrence of characteristic " Middle Tertiary" shells in the Diablerets, 
 proves that the greatest movements of the Alps belonged to an epoch 
 subsequent to the establishment of the Cerithium plicatum and many 
 contemporary species in the Tertiary seas. 
 
 I am not yet prepared to divide the Miocene strata of Europe into 
 Upper, Middle, and Lower, although the time is not far distant when 
 such a subdivision will become necessary and possible. Meanwhile, the 
 following modification of the Table at pp. 104, 105, is proposed, con- 
 sisting simply of a substitution of the term "Lower Miocene" for 
 " ^PP er Eocene," and of a subdivision of the Middle Eocene of the 
 same Table into two parts. 
 
 Proposed Modification of the Table of Fossiliferous Strata, 
 pp. 104-105. 
 
 6. 
 
 7 B. 
 
 UPPER 
 MIOCENE, 
 
 G. LOWER 
 MIOCENE. 
 
 7 A. UPPER 
 EOCENE. 
 
 MIDDLE 
 EOCENE. 
 
 British Examples. 
 Wanting in the British Isle* 
 
 Hempstead Beds, Isle of Wight, 
 p. 102. 
 
 1. Bembridge Beds, Isle of Wight, 
 p. 203. 
 
 2. Osborne Series, p. 210. 
 
 3. Headon Series. Ibid. 
 
 4. Barton Clay, p. 212. 
 
 fl.B 
 
 {,'v 
 
 Bagshot and Bracklesham Beds, 
 
 p. 213. 
 
 Wanting. 
 
 8. LOWER EOCENE. As in the table, p. 105. 
 
 Foreign Equivalents and Synonyms. 
 Faluns of Touraine, p. 175. 
 Bolderberg Strata in Belgium, p. 
 
 178. 
 Sansans, near Pyrenees, South of 
 
 France. 
 . Basin of Vienna, p. 179. 
 
 Ores de Fontainebleau, p. 194. 
 
 Calcaire de la Beauce. Ibid. 
 
 Mayence basin, p. 190. 
 
 Limburg beds, Belgium, p. 188. 
 
 "Oligocene" strata of North Ger- 
 many. 
 
 Nebraska beds in United States, p. 
 206. 
 
 1. Gypseous Series of Montmartre, 
 
 p. 223. 
 2 & 3. Calcaire Siliceux, p. 225 ; 
 
 or Travertin inf6rienr. 
 4. Gres de Beauchamp, or Sables 
 
 Moyens, p. 226. 
 4. Laeken beds, Belgium. 
 
 1. Calcaire Grossier of Paris basin, 
 p. 226. 
 
 2. Upper Soissonnais, Sands of 
 Cuisse-Lamotte, p. 228. 
 
 1 & 2. Nummulitic formation of 
 Europe, Asia, &e., p. 229. 
 
DENUDATION OF WEALDEN. 645 
 
 MIOCENE FAUNA OF THE SEWALIK HILLS, p. 182. 
 
 THE genus Dinotkerium, so characteristic of the Falunian or Upper 
 Miocene period in Europe, occurs in India in strata of the same age. 
 But as yet it has only been found in Perim Island, in the Gulf of Cam- 
 bay, and not among the fossils of the Sewalik or Sub-Himalayan Hills, 
 as stated by mistake in the text (p. 182). Seven species of Sewalik 
 elephants have been alluded to, whereas the number is in fact only five, 
 three of which are referred by Dr. Falconer to the sub-genus Stegodon, 
 comprising forms intermediate between the Mastodon and Elephant. 
 The hippopotamus mentioned in the same page (182), belongs to the 
 sub-genus Hexaprotodon, a form now extinct. The Anoplotherium 
 posterogenium, supposed when first discovered to present a generic link 
 between the Sewalik fauna and that of the Eocene period, is now rec- 
 ognized as a species of Chalicotherium (Anisodon of Lartet), a genus of 
 pachyderms intermediate between the Rhinoceros and Anoplothere. The 
 same genus occurs in Miocene- or Falunian strata at Sansan, in the 
 department of Gers, in the South of France. Among the Sub-Himalayan 
 fossils, a giraffe, camel, and large ostrich may be cited as proofs that 
 there were formerly extensive plains where now a steep chain of hills, 
 with deep ravines, runs for many hundred miles east and west. 
 
 Fifteen species of freshwater shells of the genera Paludina, Melania, 
 Ampullaria, and Unto were obtained by Sir P. Cautley and Dr. Fal- 
 coner from the same strata, and, when shown by them in 1846 to the 
 late Prof. E. Forbes, were pronounced by him to be all extinct or un- 
 known species, with the exception of four, which are still inhabitants of 
 Indian rivers. Such a proportion of living to extinct species of Mol- 
 lusca agrees well with the usual character of an upper Miocene or 
 Faluniau fauna, as cbserved in Touraine, or in the basin of Vienna and 
 elsewhere. 
 
 DENUDATION OF THE WEALDEN. (Ch. XIX. pp. 2*71, 285.) 
 
 Denudation of the Wealden Discovery of the Lower Crag on the summit of 
 the. North Downs between Folkestone and Dorking. 
 
 THE arguments adduced in the 19th chapter, pp. 271 285, to prove 
 that the denudation of the Wealden area took place at many successive 
 periods, and at dates widely remote from each other, some of them an- 
 tecedent to the deposition of the Lower Eocene strata of Great Britain, 
 and others so late as the Pliocene epoch, have lately received an unex- 
 pected confirmation, for Mr. Prestwich has announced to the Geological 
 Society of London (January 21st, 1857) the discovery of marine sands 
 
646 LOWER CRAG ON NORTH DOWNS. 
 
 of the crag period, resting on the summit of the North Downs at vari- 
 ous points between Folkestone and Dorking. These ferruginous sands 
 include layers of iron sandstone, and of quartzose sand, with flint peb- 
 bles, and occasionally green earth, the whole deposit resembling pre- 
 cisely in mineral character the sands of Diest, in Belgium, -which have 
 long been considered as of the same age as the older crag of Suffolk. 
 The same Terebratula grandis, which abounds in the English crag, and 
 in the sands of Diest ; and the casts of Astarte, Pyrula, and other fos- 
 sils, concur with the mineral character of the beds to prove the con- 
 temporaneous origin of these British and Belgian strata. At Paddles- 
 worth, 4 miles W.N.W. of Folkestone, the irony sands, above mentioned, 
 rest on an older flint gravel, at an elevation of between 600 and 700 
 feet above the sea, and near the edge of the chalk escarpment. Some 
 idea of their exact position may be gained by the reader by supposing 
 them placed on the heights marked by the strong black line above fig. 
 3, in the woodcut 321 (p. 272 of the text of this edition, and 4th edition 
 p. 243), or he may suppose the tertiary outlier 6, fig. 329 (p. 282 of this 
 edition), to consist of Coralline crag, instead of being a mass of Eocene 
 clay and sand. 
 
 It follows from such facts, that although the first elevation of the 
 Wealden took place, as shown in the 19th chapter, in the early Eocene, 
 or partly, perhaps, in the cretaceous period ; and although much denu- 
 dation was then effected, yet the same area was again submerged during 
 the Older Pliocene epoch. The latest denudation, therefore, as well as 
 the present escarpments, were brought about after the sea had become 
 already peopled with species of mollusca, half of which are still living. 
 The great upheaval of land in the Wealden area, thus proved to be 
 subsequent in date to the Lower Crag, may, as Mr. Prestwich observes, 
 help to explain the difference observed in the fauna and climate of the 
 several successive crag periods (see above, p. 636) ; for we may now with 
 more confidence assume that the sea of the Coralline Crag was open to 
 the south, so that shells of southern forms lived in it, until at length, 
 the bed of th;*t sea having upraised 650 or 700 feet, all communication 
 with warmer latitudes was cut off, and the fauna of the Red Crag ac- 
 quired its more boreal character. 
 
 We also learn from these recent discoveries how impossible it may 
 often be to demonstrate the former presence of the sea on any given area 
 by organic remains, or by sea-beaches. Long and diligent inquiries had 
 been made before the year 1856, for sea shells of recent or crag species, 
 and for the signs of old sea margins within the Wealden area, or on 
 Nos. 3, 4, 5, 6, and 7 of the map (p. 272 of this edition, and p. 242, 4th 
 edition), and on the chalk downs and tertiary area between the Weald 
 and the Thames (Nos. 1 and 2, ib.) ; but in vain, until at last a few 
 casts of shells prove incontestably the long sojourn of the Older Pliocene 
 sea in those very spaces. We must now, therefore, admit the retreat of 
 its waters to have been an event of times comparatively modern. It 
 follows that in many cases the lnd may have sunk and have emerged 
 
NEW OOLITIC MAMMALIA. 647 
 
 again without retaining on its surface any monuments of the kind 
 usually demanded as indispensable to warrant us in speculating on 
 marine denudation as a great modifying cause in the physical geography 
 of the globe. 
 
 NEW FOSSIL MAMMALIA FROM THE PURBECK OR UPPER OOLITIC 
 STRATA IN DORSETSHIRE. 
 
 Discovery in Dorsetshire of seven or eight new genera of Mammalia in the Pur- 
 beck or Upper Oolite strata First example of a skull of a Mammifer from 
 Secondary Rocks Insectivorous Marsupials and Placentals and herbivorous 
 Marsupials Figures and descriptions Light thrown on the Microlestes or 
 oldest triassic Mammifer General bearing of the new facts. 
 
 IT will be seen by the text (p. 457) that when the 5th edition of this 
 work was published two years ago, six species only of mammalia were 
 known in the whole world from rocks older than the Tertiary. The 
 researches of 36 years had been required to bring these six species to 
 light, from 1818, when first a lower jaw from the Stonesfield Oolite, 
 found 10 years before, was pronounced by Cuvier to be mammalian, 
 to the year 1854, when the Spalacotkerium of Purbeck was described 
 by Owen. 
 
 Figures are given at p. 341 of two small molar teeth of the most an- 
 cient of these six quadrupeds, the Microlestes of Plieninger, found in a 
 bone-bed near Stuttgart usually referred to the Upper Trias, and in 
 which Triassic species of fish and reptiles abound. Figures are also 
 given of the fossil lower jaws with teeth of three diminutive mammalia 
 obtained from the inferior oolite of Stonesfield (pp. 311-12 of the text, and 
 368, 4th ed.), and supposed to belong to insectivorous creatures, one of 
 them at least to a marsupial quadruped. The remains of a fourth 
 British mammal, also consisting of a lower jaw from the same locality, 
 found by the Rev. J. B. P. Dennis, and made known in September, 
 1854, is alluded to in a note at p. 457. Although small, it was con- 
 siderably larger than the three species previously discovered, being 
 probably about the size of a rabbit. Professor Owen imagines it to have 
 been of omnivorous habits, and one of the ungulate or hoofed quad- 
 rupeds, allied to certain extinct genera of the tertiary period, called 
 Hyracotherium, Microtheriurn and Hyopotamus. 
 
 The discovery in Purbeck, Dorsetshire, in 1854, of the Spalacotherium, 
 a small insectivore allied to the Cape mole, is mentioned at p. 295 and 
 457, as the first example of a mammifer from those freshwater strata. 
 In December last (1856) Mr. Samuel H. Beckles, F. G. S., conversed 
 with me in London on the desirability of quarrying the Middle Purbeck 
 in Durlestone Bay, near Swanage, for the express purpose of exploring 
 the fossil contents of the bed in which Mr. W. R. Brodie had procured 
 
648 NEW SPECIES OF MAMMALIA 
 
 the Spalacotherium. The average thickness of this stratum called No. 
 93, or the " dirt-bed," is about 5 inches.* It lies at the base of the 
 middle Purbeck, and consists of a soft marl, or calcareous mud, and con- 
 tains the remains of a few insects with freshwater shells of several genera 
 (Paludina, Planorbis, and Cyclas), and many reptiles. As the fruit of 
 his second day's excavations (Dec. llth) Mr. Beckles sent me the lower 
 jaw of a mammal of a new genus, a discovery soon followed by others 
 in rapid succession, so that at the end of three weeks there were disin- 
 terred from an area not exceeding 40 feet in length by 10 feet in width, 
 the remains of five or six new species 'belonging to three or four distinct 
 genera, varying in size from that of a mole to that of a hedgehog, be- 
 sides the entire skeleton of a crocodile, the shell or carapace of a fresh- 
 water tortoise, and some smaller reptiles. While these investigations 
 were in progress, Mr. W. R. Brodie of Swanage kindly forwarded to 
 me at my request the fossils which he had been accumulating during 
 two years (1855 and 1856) from the same thin bed in a contiguous area 
 no less limited in its dimensions. Besides reptilian remains, there were 
 among his acquisitions three lower jaws of three mammalian species, 
 and Dr. Falconer, who interpreted for me the meaning of these and 
 other fossils, as they arrived from day to day, called my attention to one 
 slab in which was seen the upper portion of a skull, consisting of the 
 two parietal bones in a good state of preservation, with the sagittal 
 crest well marked, as also the connection with the frontals and the oc- 
 cipital crest. Although the lateral and basal portions of this cranium 
 are wanting, enough remains to show that it agrees with the ordinary 
 type of living warm-blooded quadrupeds, implying probably a higher 
 organization than that of such genera as the Stonesfield Phascolotherium 
 and Amphitherium, though affording no clear evidence whether the 
 creature was placental or marsupial. It is singular that this specimen 
 should have been the first example ever seen of a cranium, or indeed of 
 any part of the skeleton of a mammifer other than a lower maxillary 
 bone with teeth, from rocks more ancient than the tertiary. It supplied 
 therefore a more significant kind of evidence to the osteologist than had 
 previously been obtained of the exact correspondence in structure of 
 the mammalia of a very remote period with the higher types of living 
 vertebrata. 
 
 In the same slab with the cranium is one entire side of a lower jaw 
 of a quadruped, for which Professor Owen proposes the generic name 
 of Triconodon. It contains eight molars, a large and prominent canine, 
 and one broad and thick incisor. This creature must have been nearly 
 as large as the common hedgehog.f 
 
 This so-called " dirt-bed" is designated as No. 93 both in the Guide to the 
 Geology of the Isle of Purbeck, by the Eev. G. H. Austen (1852), and by the 
 Rev. 0. Fisher, in his paper on the Purbeck strata. Trans. Carab. Phil. Soc., 
 vol. Ix. (1855). It has not the character of an ancient vegetable soil, as the 
 name would seem to imply. 
 
 f The compressed crowns of the inferior molars in this Triconodon have each 
 
FROM THE PURBECK OOLITE. 649 
 
 Several other jaws with similar tricuspid teeth of larger dimensions, 
 found by Mr. Beckles, indicate the existence of another species of Tri- 
 conodon of a more elongated form, and about one-third larger in size. 
 From one of these the following evidence of its marsupial character was 
 pointed out to me by Dr. Falconer. 1. The plurality of true molars. 
 2. The strong, inflected angular process. 3. (And this is considered 
 by him the most significant of all), the broad, salient, everted rim of 
 the ridge which is decurrent on the outer side from the condyle along 
 the inferior margin, exactly as in the carnivorous marsupials. 4. The 
 marked development of the mylo-hyoid groove. He also adds, that 
 these two species of Triconodon, from the cutting character of their 
 teeth, and their comparatively formidable canines, together with the 
 form of the ascending ramus, are more like small ferine animals than 
 mere insectivorous marsupials. It is most probable that they fed on 
 prey less minute than insects. 
 
 Among the jaws of many smaller insectivora is one allied to the type 
 of the Stonesfield Amphitherium, but generally distinct.* 
 
 The following observations by Professor Owen, on the genus Tri- 
 conodon, extracted from a letter which I received from him January 27, 
 1857, are not the less interesting as having been written before the 
 more decisive proofs above enumerated of the marsupial characters of 
 Triconodon had been elicited from more perfect specimens obtained 
 about a month later : " The Purbeck fossil (the smaller Triconodon) 
 is most nearly allied to the Stonesfield insectivorous genera, and shows 
 characters intermediate between Phascolotherium and Thylacotherium. 
 The three-coned tooth presents the same type as in the molars of 
 these genera, but the first and third cones are developed to nearer 
 equality with the second or mid-cone. The cingulum in Triconodon 
 develops the same front and back talon. In the size of the canine, 
 and in the depth and other proportions of the jaw, Triconodon resem- 
 bles Phascolotherium, and so much so in the jaw-bone characters that 
 if one be marsupial the other should be; but I cannot get a clear 
 evidence of the inward bend of the angle, or of its extension back- 
 wards. 
 
 "In the superior number of molars, Triconodon resembles Tliyla- 
 cotherium, and also Myrmecobius, which, by the way, has a somewhat 
 similar type of molar tooth. The above-cited genera and Spalacothe- 
 rium have enough of characters in common, so far as regards mandible 
 and mandibular teeth, to suggest their all belonging to the same natural 
 
 of them three subequal sharp-pointed cusps, rising nearly vertically into the 
 same longitudinal plane, with basal end lobules, but without additional interior 
 complication. They are so arranged, in a continuous and compact series, as to 
 present a uniform serrated edge, like the teeth of a saw. Dr. Falconer. 
 
 * In this species the lower jaw has an elongated slender ramus, containing 7 
 uniform back molars in situ, and the empty alveoli of 4 or 5 false molars in 
 front, together with a prominent laniariform tooth. The dental formula agrees 
 numerically with that of the Amphitherium, but differs from it in the double- 
 rowed and complex arrangement of the crown-cusps. Dr. Falconer. 
 
650 
 
 HERBIVOROUS MARSUPIALS 
 
 group of an insectivorous and very probably marsupial family. The 
 character of the calvarium of Triconodon offers nothing adverse to the 
 above views."* 
 
 Besides the mammalia above alluded to, belonging to 9 or 10 species 
 and to 5 or 6 genera, all of them insectivorous or predaceous, we are 
 indebted to Mr. Beckles for having disentombed (January 31, 1857,) the 
 remains of another genus exceedingly unlike the rest, the relations of 
 
 J -. i. 
 
 Plagiaulax Secklesii, Falc. 
 
 These two figures represent the same right ramus of the lower jaw seen on the opposite sur- 
 faces of a split stone, the two taken together affording data for a complete restoration of the jaw. 
 
 Upper figure (outer side). 
 
 a, 6, e'. Eight ramus of lower jaw magnified two diameters, a, ft, outer side. &, o', d', e', im- 
 pression of inner side. 
 a. Incisor. 
 
 ?>, c. Line of vertical fracture behind the pre-molars. 
 d'. Impression of the condyle in the matrix. 
 e'. Impression of top of coronoid process. 
 
 / Section of the anterior piece of the jaw at the fracture &, c, CP, inner surface ; y, outer. 
 The notch at the top is formed by one of the sockets of the double-fanged true molar. 
 g. Section of the hinder piece near &, c; sr, inner; ?/, outer surface. 
 o'. Broken off inflected fold of inner margin buried in the matrix. 
 m. Sockets of two molars. 
 p, m. Three pre-moiars, the third and last divided by a crack. 
 
 Lower figure (inner side). 
 
 a', d. Same lower jaw on the opposite slab of stone; &, d, e, inner side; Z>, a', h, cast and im- 
 pression of outer side. 
 a'. Outline of the incisor restored. 
 J, c. Line of vertical fracture. 
 tl. Condyle. 
 e. Coronoid. 
 
 h. Impression on the matrix of the three pre-molars. 
 i. Empty sockets of the two true molars. 
 n. Orifice of dentary canal. 
 
 o. Indication of the raised and inflected fold of the posterior inner margin. 
 k. Third or largest pre-molar, magnified 5i diameters, showing the 7 diagonal grooves. 
 /. Corresponding pre-molar in the recent Australian Hypsiprymnus Gaiinardi, showing the 
 7 vertical grooves, magnified 3 diameters. 
 
 Allusion is here made to the crown of the skull before mentioned as occur- 
 ring in the same slab. In the text, at p. 295, I have cited the opinion given 
 by Professor Owen in 1854 (see Geol. Quart. Journ., vol. x. p. 431), that the 
 Spalacotherium was " more nearly allied to the placental than to the marsupial 
 insectivora," an opinion which, as will be seen, he is now disposed to modify. 
 
FEOM THE PURBECK OOLITE. 
 
 651 
 
 which to the living kangaroo-rat were immediately recognized by Dr. 
 Falconer on its first arrival in London.* 
 
 No less than 10 species of the living genus Hypsiprymnus, com- 
 monly called the kangaroo-rat, and referred by Waterhouse to the Ma- 
 cropodidce, or kangaroo family, inhabit the prairies and scrub-jungle of 
 Australia, feeding on plants and gnawing scratched-up roots. A strik- 
 ing peculiarity of their dentition, one in which they differ from all 
 other quadrupeds, consists in their having a single large pre-molar, the 
 enamel of which is furrowed with 7 vertical grooves (see ?, fig. 1, where 
 the pre-molar of the recent Hypsiprymnus Gaimardi is represented). 
 
 The largest pre-molar in the fossil genus exhibits in like manner 
 seven parallel grooves, producing by their termination a similar serrated 
 edge in the crown ; but their direction is diagonal, a distinction, says 
 Dr. Falconer, which is " trivial, not typical." 
 
 As these oblique furrows form so marked a character of the majority 
 of the teeth, Dr. Falconer has proposed for the fossil the generic name 
 of Playiaulax. The shape and relative size of the incisor a, figs. 1 
 and 2, exhibit a no less striking similarity to Hypsiprymnus. Never- 
 
 Fig.2. 
 
 Plagiaulax minor, Falc. 
 (Magnified 4 diameters.) 
 
 All the teeth in this specimen are in place and well preserved. The hinder part of the jaw- 
 bone, with the ascending ramus and posterior angle, are broken away. 
 
 a, 5. Eight ramus of lower jaw, with all the teeth magnified 4 diameters. 
 
 a. Incisor with po'int broken off. a', impression of same, showing that the inner side, near 
 
 the apex was hollowed out in a longitudinal direction. 
 
 b. Offset of coronoid, the rest of which is wanting. 
 m. The two true molars. 
 
 p, m. The four pre-molars. 
 
 c. The first molar, magnified 8 diameters. 
 
 Upper figure, the crown. Lower figure, side view. 
 
 d- s-^cond molar, crown and side view. 
 e. Straight line indicating the length of the jaw, natural size. 
 
 theless, the more sudden upward curve of this incisor, especially in 
 the larger species, as well as the number and characters of the other 
 teeth, and the shortening compression and depth of the jaw, taken 
 together with the backward projection of the condyle (</, fig. 1), indi- 
 cate a great deviation in the form of Plagiaulax from that of the living 
 kangaroo-rats. 
 
 All the information concerning the natural history, osteology, and affinities 
 of Plagiaulax given in the following pages, is extracted from a more detailed 
 paper by Dr. Falconer, shortly to be published by the Geological Society, the 
 MS. copy of which has been liberally placed at the author's disposal. 
 
652 HERBIVOROUS MARSUPIALS 
 
 Our knowledge is at present confined to two specimens of lower 
 jaws,* evidently referable to two distinct species, extremely unequal 
 in size, and otherwise distinguishable. The largest, P. Bedclesii (fig. 1), 
 was about as big as the English squirrel or the flying phalanger of 
 Australia (Petaurus Australis, Waterhouse). The skeleton of this 
 phalanger (named P. macrurus, No. 1849, Museum of College of Sur- 
 geons) measures 15 inches in length, exclusive of the tail, which is more 
 than 11 inches long. The smaller fossil (P. minor, fig. 2), having 
 only half the linear dimensions of the other, was probably only 1-1 2th 
 of its bulk. To the geologist, however, it is perhaps the more interest- 
 ing of the two, as Dr. Falconer has recog- 
 Fig> a nized in its two back molars (c, c?, fig. 2) aii 
 
 unmistakable resemblance to those of the 
 Triassic Microlesies (&, c, fig. 3). 
 
 Of this most ancient of known fossil mam- 
 malia an account is given in the text at p. 
 T lL?ngef Zm^rlSS 341 with ^lustrations, among which, how- 
 Trias of Wirtemburg. ever, there was LI o figure of the crown of 
 
 &. Crown of the smaller molar (b, , , , ,.,. i-i-i-i 
 
 fig. 441, p. 341, of the text) the larger molar, which is now added, with 
 c Cro\vn of 6 larger tooth (6- 442 a new illustration of the crown of the smaller 
 ' e tooth. No naturalist on the Continent to 
 
 whom I had previously shown casts and 
 drawings of these teeth, had been able to give any feasible conjecture 
 as to its affinities. Plieninger considered it to be predaceons, whence 
 the name; others fancied they saw some likeness in the form of its 
 grinders to those of an omnivorous pachyderm, as well as of an Insec- 
 tivore ; while Professor Owen, at once recognizing the mammalian char- 
 acter of the double-fanged teeth, said they were distinct from any type 
 known to him. When these grinders of Microlestes (fig. 3) are com- 
 pared to those of Plagiaulax minor (d, c, fig. 2), the reader will agree 
 with Dr. Falconer, that "had they all been found detached in the 
 same slab they might have been taken for back and front, or for upper 
 and lower teeth of the same or some cognate species, the essential 
 characters of the crown being identical ;f whereas, had the last molar 
 and last pre-molar of Plagiaulax been found fossil under similar cir- 
 cumstances, they would in all probability have been taken for teeth not 
 merely of different genera, but even of different orders of mammalia." 
 
 Two principal questions, observes Dr. Falconer, deserve our con- 
 sideration with reference to Plagiaulax; namely, first, Was it mar- 
 
 * Three additional specimens of P. Becklesii have since arrived, some with 
 the two back molars entire. They confirm all the conclusions set forth in the 
 following pages, and especially the affinity of Plagiaulax and Microlestes. 
 
 f The last back molar, whether of Microlestes or Plagiaulax, has two opposed 
 longitudinal marginal ridges, more or less lobed or crenated, and separated by 
 a depressed disk. In the next or larger molar of Plagiaulax, the cusps are not 
 symmetrical on the two sides, there being two on the inner, and only one alter- 
 nating lobe on the outer ; and such seems to have been the case in the larger 
 imperfect tooth of Microlestes (c, fig. 3). 
 
FROM THE PURBECK OOLITE. 653 
 
 supial? secondly, Was it herbivorous? The general resemblance of 
 the jaws and teeth to those of the living Kangaroo-rats raises at once a 
 strong presumption in favor of the affirmative on both these points. 
 There is, as before noticed, a distinct indication in the fossil of a bend- 
 ing inwards, or towards the observer, of the posterior inner margin of 
 jaw o, fig. 1 (lower figure), stretching from the anterior boundary of 
 the dentary foramen n. The significance of this character will be ap- 
 preciated by referring to what was said of such an inflection in reference 
 to the Stonesfield Mammalia (p. 311, figs. 379-381). In both spe- 
 cies the true molars are limited to two ; yet the jaw of P. Becklesii 
 was clearly that of an adult, having its full complement of teeth. This 
 is an unexpected number in a quadruped inferred to be marsupial, in 
 which tribe the normal number of molars should be four. In both spe- 
 cies, moreover, the true molars are dwarfed in size, as well as reduced 
 in number. 
 
 In the Kangaroo-rat there is a single grooved pre-molar and four 
 back molars, while in Plagiaulax, the true molars being reduced to 
 two, we find, as if in compensation, three or four grooved pre-molars. 
 In the pigmy flying opossum of Australia (Acrobata pygmcea) there is 
 an analogous development of pre-molars with a reduction of the back 
 grinders to three ; and in the Sub-genus Dromicia, or pigmy phalanger, 
 there are four pre-molars, while the back molars are reduced to three. 
 In the living MyrmecoUus* the true molars are greatly in excess of the 
 normal number ; while in the fossil Plagiaulax they are few and rudi- 
 mentary, fewer even than in any of the placental herbivora. It is true 
 that in general form the coronoid (e, fig. 1) of Plagiaulax resembles 
 more that of the predaceous marsupials, and of Dasyurus especially, 
 than of the herbivorous families ; but on the other hand it is less ele- 
 vated, and its surface of less area, than in the predaceous genera, whether 
 marsupial or placental. 
 
 The condyle (d, fig. 1), which is well preserved, is remarkable for its 
 depressed position, a character which, considered apart from all the 
 rest, might have been taken to indicate a beast of prey ; but it is coun- 
 terbalanced by another peculiarity without example, so far as Dr. Fal- 
 coner is aware, among the predaceous genera, whether marsupial or 
 placental ; viz., the long neck and horizontal projection of the condyle 
 d behind the coronoid e. The other leading indications imply a vege- 
 table feeder ; viz., the limited surface and moderate elevation of the 
 coronoid above the plane of the teeth, the feeble development of the in- 
 flected margin, the absence of a thick angular process, the advanced 
 position of the orifice of the dentary canal (n, fig. 1), and the offset of 
 the inflected margin above it. These characters, taken in conjunction 
 with those of the teeth, would place the Plagiaulax with the vegetable 
 feeders ; and the exceptional position of the condyle may be a special 
 modification, having reference to the abnormal character of the teeth ; 
 
 * A figure of the lower jaw of this quadruped is given in my Principles of 
 Geology, ch. ix. p. 138, 9th ed. 
 
654 NEW FOSSIL MAMMALIA 
 
 i. ., the excessive development of the pre-molars and the reduced num- 
 ber and size of the true molars. 
 
 " The condyle of Plagiaulax, therefore," observes Falconer, " incul- 
 cates an emphatic warning against too much stress being laid upon any 
 single character in Palseontological determinations." And he adds that 
 " this ancient fossil is interesting not only for its affinity to the existing 
 Kangaroo-rat of Australia, but also as seeming to furnish a crucial test 
 of the soundness, in some respects, of certain generalizations which have 
 been put forward respecting the order of the successive appearance of 
 mammalia upon the surface of the earth. It is maintained by some 
 British palaeontologists and comparative physiologists of high authority, 
 that, while there is no positive proof of serial progressive development 
 from the lower to the higher forms, there is clear evidence of another 
 order of development or passage, viz., from the general to the special, as 
 we pass from the oldest tertiary to the modern period. It is urged by 
 the advocates of this doctrine, that the mammalia of the Eocene Period 
 assimilated more to the general archetype and embryonic condition of 
 vertebrate organization, while the mammalia of later times successively 
 furnish examples of increasing deviation from the original or normal 
 type as well as of special adaptation. Among other arguments, they in- 
 sist that the earliest Eocene mammalia, both herbivorous and carnivo- 
 rous, possessed in most cases the full complement of teeth ; while forms 
 characteristic of later times, such as the Felidce and Ruminantia, are 
 remarkable for special suppression of these organs. If the generalization 
 were really of as wide an application as has been claimed for it, we ought, 
 in every great family of the mammalia, to find evidence of closer adher- 
 ence to the archetype the further we recede in time. But so far is this 
 from being the case, that Plagiaulax, the oldest well-ascertained herbiv- 
 orous mammal, presents to us the most special exception to be met 
 with in the whole range of marsupialia, fossil or recent. It had the 
 smallest number of true molars of any known genus in that sub-class ; 
 thus exhibiting at the most distant end of the chain the very characters 
 which, under the influence of the assumed law, we ought only to have 
 found in some type of existing marsupials." 
 
 While the MS. of these pages was preparing for the press (February 
 10, 1857), part of the cranium of a mammal was received from Mr. 
 Beckles, comprising the two superior maxillary bones and teeth, with 
 the intermediate palate crushed, of a small insectivore. On the right 
 side of the jaw the whole series of molar teeth and the incisors are seen. 
 The grinders are more numerous, but the dental characters, says Dr. 
 Falconer, bear a relation to those of the insectivorous genus Ericulus, 
 peculiar to Madagascar, and from the general bearing of the evidence, 
 it is presumed that the fossil was a minute Placental Insectivore.* 
 
 Although the teeth differ considerably in shape from those of the other 
 Purbeck fossils, it is just possible that this creature may be the same as some 
 of the minuter species above alluded to, and known as yet only by their lower 
 jaws. 
 
FROM THE PURBECK OOLITE. 655 
 
 This was the first example of an upper jaw with teeth of a fossil mam- 
 mal obtained from any secondary rock, and only five* such jaws were 
 procured by Mr. Beckles when the entire number found by him had 
 amounted (March 20th) to twenty-eight. The other seven specimens 
 found at Purbeck by Mr. Brodie, consisted in like manner of lower jaws ; 
 and the same may be said of the ten specimens (belonging to four spe- 
 cies) of oolitic mammalia hitherto discovered at Stonesfield. 
 
 That between forty and fifty pieces or sides of lower jaws with teeth 
 should have been found in oolitic strata, and with them only five upper 
 maxillaries, together with one portion of a separate cranium, will natu- 
 rally excite surprise.f There are no examples of an entire skeleton, nor 
 of any considerable number of bones in juxtaposition. In several por- 
 tions of the Purbeck matrix there are detached bones, often much de- 
 composed, and fragments of others apparently mammalian ; but, if all 
 of them were restored, they would scarcely suffice to complete the five 
 skeletons to which the five upper maxillaries above alluded to belonged. 
 As the average number of pieces in each mammalian skeleton is about 
 250, there must be many thousands of missing bones ; and when we 
 endeavor to account for their absence, we are almost tempted to indulge 
 in speculations like those once suggested to me by Dr. Buckland, when 
 he tried to solve the enigma in reference to Stonesfield : " The corpses," 
 he said, " of drowned animals, when they float in a river, distended by 
 gases during putrefaction, have often their lower jaw hanging loose, and 
 sometimes it has dropped off. The rest of the body may then be drifted 
 elsewhere, and sometimes may be swallowed entire by a predaceous 
 reptile or fish, such as an ichthyosaur or a shark." 
 
 We may also suppose that when fish or other aquatic animals attack 
 a decaying carcass, whether it be floating or has sunk to the bottom, 
 they will first devour those parts which are covered with flesh. A lower 
 jaw, consisting of little else than bones and teeth, will be neglected, and 
 becoming detached, may be drifted away by a current of moderate ve- 
 locity, and buried apart from the other bones in sand or mud. 
 
 Among the latest discoveries of Mr. Beckles (March 19th), is the lower 
 jaw of a small, adult, predaceous quadruped, with a robust canine and 
 only six molars, differing in this respect as well as in its other characters, 
 so far as the evidence at present extends, from the marsupial type. 
 
 The small average size of the species as yet made out is worthy of 
 notice, the two largest of them not exceeding by more than a third the 
 
 The second of these is a fragment of the facial part of the cranium of Tri- 
 conodon, received from Mr. Beckles, February 18th. It consists of the rigTit 
 maxillary bone, containing some of the molar teeth, together with a consider- 
 able portion of the palate uncrushed. 
 
 f As specimens of mammalia are arriving weekly from Mr. Beckles, we may 
 expect a great addition to the number of individuals, as well as an increase in 
 the number of species, before his labors terminate. To gain access to these 
 treasures, he has already at his own cost removed nearly 3000 tons' weight of 
 stone overlying the bed No. 93. 
 
656 FOSSIL MAMMALIA 
 
 dimensions of the common hedgehog or the squirrel. On this subject 
 Dr. Falconer observes, that in the Miocene freshwater deposit of Seissan, 
 in the Department of Gers, near the Pyrenees (so well explored by M. 
 Lartet), there is a layer in the marginal part of the basin in which the 
 bones of diminutive mammalia, such as shrews and others, are mixed 
 with remains of frogs in profusion ; while in a more central part of the 
 same basin, entire carcasses of the Mastodon and other huge animals oc- 
 cur. In like manner the thin layer No. 93 in Purbeck may represent 
 the shallow margin of a river, lake, or lagoon, in the deeper parts of 
 which fossil animals of greater size may be preserved. 
 
 On a review of all the fossils collected by Messrs. Brodie and Beckles,' 
 including the original Spalacotherium, together with a lower jaw be- 
 longing to the Rev. P. B. Brodie, and communicated to me by Prof. 
 Owen, it appears that we now possess (March 14th) the evidence of 
 about fourteen species of mammalia from the Middle Purbeck, to say 
 nothing of numerous remains of the highest osteological interest, respect- 
 ing which no opinion can be hazarded until they have been studied more 
 in detail. They belong to eight or nine genera, some insectivorous or 
 predaceous, others having affinities as yet doubtful, and one of a purely 
 herbivorous type, allied to the Kangaroo-rat of Australia. Some of the 
 predaceous species were marsupial, some of them, in the opinion of Dr. 
 Falconer, probably placental. 
 
 As all of them have been obtained from an area less than 500 square 
 yards in extent, and from a single stratum not more than a few inches 
 thick, we may safely conclude that the whole lived together in the same 
 region, and in all likelihood they constituted a mere fraction of the 
 mammalia which inhabited the lands drained by one river and its tribu- 
 taries. They afford the first positive proof as yet obtained of the co- 
 existence of a varied fauna of the highest class of vertebrata with that 
 ample development of reptile life which marks all the periods from the 
 Trias to the Lower Cretaceous inclusive, and with a gymnospermons 
 flora, or that state of the vegetable kingdom when cycads and conifers 
 predominated over all kinds of plants, except the ferns, so far at least 
 as our present imperfect knowledge of fossil botany entitles us to speak. 
 
 The annexed table will enable the reader to see at a glance how con- 
 spicuous a part, numerically considered, the mammalian species of the 
 Middle Purbeck now play when compared with those of other forma- 
 tions more ancient than the Paris gypsum, and at the same time it 
 will help him to appreciate the enormous hiatus in the history of fossil 
 mammalia, which at present occurs between the Purbeck and Eocene 
 Periods.* 
 
 In drawing up this table I have been assisted by Professor Owen, in refer- 
 ence to the British, and by MM. Lartet and Hebert in reference to the fossil 
 mammalia of the French Eocene strata. There are, besides, several undescribed 
 species in the collection of the two last-mentioned paleontologists, or in mu- 
 seums known to them ; and in regard to one or two of the Eocene continental 
 localities out of the Paris basin, the age of the deposits is too little known to 
 allow us to include their fossils in the Table. 
 
IN SECONDARY ROCKS. 
 
 657 
 
 Number and Distribution of all the known Species of Fossil Mamma- 
 lia from Strata older than the Paris Gypsum, or than the Bembridge 
 Series of the Isle of Wight. 
 
 Headon Series and Beds between the] {IATT. v i, 
 Paris Gvpsum and the Gres de Beau- -}- 14 \ ngll l n ' 
 champ.".:: J 1 Drench. 
 
 Barton Clay and Sables de Beauchamp .... 
 
 Bagshot Beds, Calcaire Grossier, and) fft P? 
 
 TERTIARY. 4 ^PP- Soissonnais of Cuisse-I^motte. [ ^ ( * 
 
 London Clay, including the Kyson Sand . . 7 All English. 
 Plastic Clay and Lignite 9J J'gjJ^ 
 
 Sables de Bracheux 1 French. f 
 
 Thanet Sands and Lower Landenian of f Q 
 
 Belgium j 
 
 Maestricht Chalk 
 
 White Chalk 
 
 Chalk Marl 
 
 Upper Green Sand 
 
 Gault 
 
 Lower Green Sand 
 
 Weald Clay, &c 
 
 Hastings Sand 
 
 Upper Purbeck Oolite 
 
 Middle Purbeck Oolite 14 Eng. (Purbeck). 
 
 Lower Purbeck Oolite 
 
 SECONDARY. -! Portland Oo lite 
 
 Kimmeridge Clay 
 
 Coral Rag 
 
 Oxford Clay 
 
 Great Oolite 4 Eng. (Stonesfield). 
 
 Inferior Oolite 
 
 Lias 
 
 "w i 
 
 Middle 
 
 Lower 
 
 Permian 
 
 Carboniferous 
 
 PRIMARY. i Silurian 
 
 Cambrian 
 
 After what has been said at the close of the 27th chapter, pp. 457, 
 459, and at p. 402, ch. xxv., I have little to add in regard to the bear- 
 ing of these discoveries in Purbeck on some geological theories hastily 
 embraced, in favor of the non-existence or scarcity, at particular periods, 
 of certain classes of air-breathing animals, on the ground of our not 
 happening at present to have met with any fossil representatives of the 
 same. It is worthy, however, of notice, that in' the Hastings Sands 
 there are certain layers of clay and sandstone in which numerous foot- 
 prints of quadrupeds have been found by Mr. Beetles, and traced by 
 
 I allude to several Zeuglodons found in Alabama, and referred by some 
 zoologists to three species. 
 
 f The Sables de Bracheux, although somewhat older than the Plastic clay are 
 supposed by Mr. Prestwich to be newer than the Thanet Sands. They have 
 yielded at La Fere the Arctocyon (Palceocyori) primcevus, the oldest known tertiary 
 mammal. 
 
 42 
 
658 OOLITIC MAMMALIA. 
 
 him in the same set of rocks through Sussex and the Isle of Wight 
 They appear to belong to 3 or 4 species of reptiles, but no one of them 
 to any warm-blooded quadruped. They ought, therefore, to serve as a 
 warning to us, when we fail in like manner to detect mammalian foot- 
 prints in older rocks (such as the New Red Sandstone), to refrain from 
 inferring that quadrupeds, other than reptilian, did not exist or pre-exist. 
 
 But the most instructive lesson read to us by the Purbeck strata con- 
 sists in this : They are all, with the exception of a few intercalated 
 brackish and marine layers, of fresh water-origin ; they are 160 feet in 
 thickness, have been well searched by skilful collectors, and by the late 
 Edward Forbes in particular, who studied them for months consecu- 
 tively. They have been numbered,. and the contents of each stratum 
 recorded separately, by the officers of the Government Survey of Great 
 Britain. They have been divided into three distinct groups by Forbes, 
 each characterized by the same genera of pulmoniferous mollusca and 
 cyprides, but these genera being represented in each group by different 
 species ; they have yielded insects of many orders, and the fruits of 
 several plants ; and lastly, they contain " dirt beds," or old terrestrial 
 surfaces and soils at different levels, in some of which erect trunks and 
 stumps of cycads and conifers, with their roots still attached to them, 
 are preserved. Yet when the geologist inquires if any land animals of 
 a higher grade than reptiles lived during any one of these three periods, 
 the rocks are all silent, save one thin layer a few inches in thickness, 
 and this single page of the earth's history suddenly reveals to us in a 
 few weeks the memorials of so many species of fossil mammalia, that 
 they already outnumber those of many a subdivision of the tertiary 
 series, and far surpass those of all the other secondary rocks put to- 
 gether ! 
 
 It is remarked by Professor Owen that many of the Purbeck Insec- 
 tivora belong to the same natural family as those of Stonesfield. Some 
 at least of them were Marsupials, and Dr. Falconer has pointed out 
 that the Plagiaulax of Purbeck, an herbivorous marsupial, was so much 
 allied to the Microlestes of the Trias as to lead us to infer that that 
 more ancient mammifer was likewise a pouched quadruped, having some 
 affinity to the living Kangaroo-rat. 
 
 In Australia and the neighboring islands about 100 species of mar- 
 supials exist, together with a certain number of placentals (bats and 
 rodents), while the fossil species of that continent show that kangaroos, 
 wombats, Tasmanian wolves (or Thylacines), dasyures, and other mar- 
 supials of species now extinct, preceded the present creation. Although 
 the localities of Stuttgardt, Stonesfield, and Purbeck, do not relate to 
 an area larger than the middle island of New Zealand, yet there may 
 have prevailed, during the Oolitic period, throughout a much wider 
 space in European latitudes, certain geographical and climatal condi- 
 tions and a peculiar vegetation, favorable to a fauna more analogous to 
 that of the present Antipodes than to that of modern Europe. During 
 the Upper Triassic, the Liassic, and Oolitic epochs, one assemblage of 
 
UPPER TRIAS OF EASTERN ALPS. 659 
 
 such quadrupeds may have succeeded to another, until at a later era, 
 and after the interval marked by the Wealden and Cretaceous rocks, 
 another and a different geographical state of things being established, 
 the tertiary mammalia of Europe entered on the stage and occupied the 
 same area. 
 
 The advocates, however, of the doctrine of progressive development 
 will offer a different explanation of the phenomena. They will refer the 
 large admixture of marsupials in the Stonesfield and Purbeck fauna to 
 chronological rather than to climatal conditions, to the age of the 
 planet rather than to the state of a portion of its dry land. In the 
 Triassic and Oolitic periods they will say the time had not yet come 
 for the creation or development of more highly organized beings. Ex- 
 perience must test and determine the soundness of these theoretical 
 views. In the mean while it may be useful to bear in mind that while 
 Australia supports at present 100 species of marsupials, the rest of the 
 continents and islands of the globe are tenanted by about 1,700 species 
 of mammalia, of which only 46 are marsupials (namely, the opossums 
 of North and South America), and in like manner there flourished in 
 the Pliocene period throughout Europe, Asia, and America, so far as we 
 yet know, a placental fauna, consisting of species now for the most part 
 extinct, which was coeval with the extinct Pliocene marsupials of Aus- 
 tralia. Such facts, although far to limited to enable us to generalize 
 with confidence, seem rather to imply that at certain periods of the 
 past, as in our own days, the predominance of certain families of terres- 
 trial mammalia has had more to do with conditions of space than of 
 time ; or in other words, has been more governed by geographical cir- 
 cumstances than by a law of successive development of higher and 
 higher grades of organization, in proportion as the planet grew older. 
 
 DISCOVERY OF MAMMALIAN REMAINS IN ROCKS OF HIGH ANTIQUITY 
 IN NORTH CAROLINA, UNITED STATES. 
 
 ALTHOUGH only six weeks have elapsed since the foregoing remarks on 
 the Purbeck mammals appeared in the first edition of this Supplement, 
 a remarkable addition has already been made during this short interval 
 to our knowledge of the ancient geographical range of Secondary 
 Mammalia. Dr. Emmons, in the newly published volume of his "Amer- 
 ican Geology" (Part VI. p. 93), announces that last year (1856) he 
 met with three lower jaws of an insectivorous mammal in the Chatham 
 Coal-field in North Carolina. He has given a figure of the outside of 
 the ramus of one of these jaws, nine-tenths of an inch in length, con- 
 taining ten molars in a continuous series, one canine, and three incisors. 
 The three posterior molars are tricuspid, as in Spalacotkerium ; the 
 four next, multicuspid; and the three anterior ones are simple, conical, 
 
660 MARINE UPPER TRIAS 
 
 and slender. The incisors are separated, as in Phascolotherium, a 
 marsupial characteristic. The structural form of the jaw, according to 
 Dr. Emmons's figure, shows some points of analogy with Spalacotherium, 
 and some of difference. 
 
 Dr. Emmons has named the fossil Dromatherium sylvestre. He refers 
 the strata in which it was entombed to the Permian period, chiefly be- 
 cause they contain the remains of Thecodont Saurians ; but, as fossil 
 species of this family of reptiles have been met with in the Upper Trias 
 of Wirtemberg, we cannot lay much stress on this argument. This fossil 
 may at least claim an antiquity equal to that of the Richmond coal-field, 
 in Virginia, described in the text, at p. 330. If so, the Dromatherium 
 would belong to the lower part of the Jurassic series, older than the 
 Stonesfield Slate ; and therefore it must be regarded as one of the most 
 ancient representatives of the mammalian class yet discovered. 
 
 UPPER TRIAS OF THE EASTERN ALPS (p. 333). 
 
 Kecognition of a Marine equivalent of the Upper Trias in the ATM trian Alps- 
 True position of the St. Cassian and Hallstatt Beds 800 new species of triassic 
 Mollusca and Radiata Links thus supplied for connecting the Palaeozoic and 
 Neozoic faunas. 
 
 THE true position in the series of certain Alpine rocks called " the St. 
 Cassian beds" has long been a subject of doubt and discussion, but the 
 researches of many eminent geologists, among others MM. Von Buch, 
 E. de Beaumont, Murchison, and Sedgwick, and in Switzerland, MM. 
 Escher and Merian, and more lately in Austria, MM. Von Hauer, Suess, 
 and Homes, have shown that these rocks are unquestionably referable 
 to the Keuper or Upper Trias. It has also been proved that the Hall- 
 statt beds on the northern flanks of the Austrian Alps correspond in age 
 with the St. Cassian beds on their southern declivity. By these discov- 
 eries we become acquainted, suddenly and unexpectedly, with a rich 
 marine fauna belonging to a period previously believed to be very barren 
 of organic remains, because in England, France, and Northern Germany, 
 the Upper Trias is chiefly represented by beds of fresh or brackish 
 water origin. Mr. Edward Suess, of Vienna, to whom we are indebted 
 for several memoirs on the rocks in question, has favored me with the 
 following summary of the order of succession of the Hallstatt beds in 
 the Austrian Alps, which I had an opportunity, when travelling in the 
 autumn of 1856, of verifying in company with Mr. Giimbel, of Munich. 
 
 The uppermost strata first . enumerated immediately underlie the 
 Lower Lias of the Swabian Jura. This lias is represented near Vienna 
 by a brown limestone, containing Ammonites Bucklandi, A. Cony- 
 bearii, &c. 
 
OF THE AUSTRIAN ALPS. 
 
 661 
 
 Infra-liassvc(?) Strata of the Austrian Alps, in descending Order. 
 
 Koessen beds. 
 
 (Synonyms, Upper St. 
 Cassian beds of Escher and 
 Merian ; Upper Trias ? or 
 intermediate between Lias 
 and Trias ?) 
 
 2. Dachstein beds, 
 
 between Lias and Trias ? 
 
 3. Hallstatt beds 
 
 (or St. Cassian). 
 Trias. 
 
 Upper - 
 
 Gray and black limestone with calcareous marls, 
 having a thickness of about 50 feet. Among 
 the fossils, Brachiopoda very numerous ; some 
 few species common to the genuine Lias ; many 
 peculiar. Avicida contorta, Pecten Valwiiensis, 
 Cardium Rhceticum, Avicula incequivalvis, Spirifer 
 Munsteri, Dav. Strata containing the above 
 fossils alternate with the Dachstein beds, lying 
 next below. 
 
 White or grayish limestone, often in beds 3 or 4 
 feet thick. Total thickness of the formation 
 above 2000 feet. Upper part fossiliferous, with 
 some strata composed of corals. (Lithodendron.) 
 Lower portion without fossils. Among the 
 characteristic shells are Hemicardium Wulferii, 
 Megalodon triqueter, and other large bivalves. 
 
 Red, pink, or white marble, from 800 to 1000 
 feet in thickness, containing more than 800 
 species of marine fossils, for the most part mol- 
 lusca. Many species of Orthoceras. True Am- 
 monites, besides Ceratites and Goniatites, Belemnites 
 (rare), Porcdlia, Pleurotomaria, Trochus, Monotis 
 salinaria, &c. 
 
 f A. Black and gray limestone "] 
 
 4. A. Guttensteinbeds. 150 feet thick, alternating 
 B. Werfen beds, with the underlying Wer- 
 
 base of Upper -j fen beds. 
 
 Trias? Lower Trias 
 of some geologists. 
 
 B. Red and green shale and 
 sandstone with Salt and 
 Gypsum. 
 
 Among the fossils are 
 Ceratites cassianus, Mya- 
 citesfassaensis, Naticella 
 costata, &c. 
 
 In regard to the age of the rocks above mentioned, the Koessen and 
 Dachstein beds are referred by some to the Lias, by others to the Trias, 
 while many consider them to be of intermediate date. According to 
 Mr. Suess, the Koessen beds correspond to the upper bone-bed of Swabia, 
 in which the Microlestes was 'found (see p. 341), but it should not be 
 forgotten that that stratum contains true triassic species of reptiles and 
 fish. On the whole, the beds 1 and 2 contain a very peculiar fauna, 
 and Mr. Suess remarks that some of the fossils are identical with the 
 Irish " Portrush beds" of Colonel Portlock, described in his Report on 
 Londonderry. The Koessen beds have been traced for 100 geographi- 
 cal miles from near Geneva to the environs of Vienna. 
 
 Whatever doubts may be entertained respecting the exact age of the 
 beds Nos. 1 and 2, there is now no longer any dispute that the Hallstatt 
 and St. Cassian beds agree in age with the Keuper or Upper Trias ; but 
 whether the Werfen sandstone, No. 4, should form part of the same 
 series, or, as Von Hauer inclines to believe, should be classed as the 
 equivalent of " the Bunter or Lower Trias," is still undetermined. The 
 absence of well-characterized Muschelkalk fossils in the Austrian Alps 
 renders this point very difficult to decide. Rich deposits of salt, asso- 
 ciated with the Werfen beds, incline some geologists to presume that 
 they belong to the Upper Trias. Should they be classed as " Banter," 
 the Guttenstein limestone would then correspond in position with the 
 Muschelkalk, but no Muschelkalk fossils have ever been met with in it 
 
662 
 
 ST. CASSIAN BEDS. 
 
 or in the Werfen ; while, on the other hand, the true Muschelkalk is 
 known to exist in the Italian Alps and in Hungary, so that all doubts 
 on this question must very soon be removed. 
 
 Among the 800 species of fossils of the Hallstatt and St. Cassian beds, 
 many are still undescribed ; some are of new and peculiar genera, as 
 Scoliostoma, fig. 4, and Platystoma, fig. 5, among the Gasteropoda ; 
 and Koninckia, fig. 6, among the Brachiopoda. 
 
 Fig. 4. Ffc. 5. 
 
 Platystoma Suessii, 
 
 Hoernes. 
 From Hallstatt. 
 
 Scoliostoma, S. Cassian. 
 Fig. 6. 
 
 Koninckia Leonhardi, Wissmann. 
 
 a. Dorsal view, natural size. 
 
 &. Ventral view, part of the converse ventral valve removed to show the interior of dorsal 
 
 valve and its vascular impressions. One of the spiral processes is seen through the 
 
 translucent shell. 
 
 c. Section of both valves. 
 
 d. Interior of dorsal valve, with spiral processes restored. (Suess.) 
 
 The following table of genera of marine shells from the Hallstatt and 
 St. Cassian beds, drawn up on the joint authority of MM. Suess and 
 Woodward, shows how many connecting links between the fauna of 
 primary and secondary rocks are now supplied by the Upper Trias. 
 
 Genera of Fossil Mollusca in the St. Cassian and Hallstatt Beds. 
 
 Characteristic Triassic Genera. 
 Ceratites. 
 Scoliostoma (or Coch- 
 
 learia) . 
 Naticella. 
 Platystoma. 
 Isoarca. 
 Pleurophorus. 
 Myophoria. 
 Monotis. 
 Koninckia. 
 
 Common to Older Rocks. 
 
 Cyrtoceras. 
 
 Orthoceras. 
 
 Goniatites. 
 
 ^Loxonema. 
 
 ^Holopella. 
 
 Murchisonia. 
 
 Euomphalus. 
 
 Porcellia. 
 
 ^Megalodon. 
 
 Cyrtia. 
 
 The genera marked by an asterisk are given on the authority of Mr. Suess, the 
 rest on that of Mr. Woodward from fossils of the St. Cassian rocks in the British 
 Museum. 
 
 Common to Newer Kocks. 
 
 Ammonites. 
 
 Belemnites. 
 
 ^Nerinasa. 
 
 Opis. 
 
 Cardita. 
 
 Trigonia. 
 
 Myoconchus. 
 
 Ostrea. 1 sp. 
 
 Plicatula. 
 
 Thecidium. 
 
ANTHOLITES OF THE COAL. 663 
 
 The first column marks the last appearance of several genera which 
 are characteristic of Paleozoic strata. The second shows those genera 
 which are characteristic of the Upper Trias, either as peculiar to it or 
 as reaching their maximum of development at this era. The third col- 
 umn marks the first appearance of genera destined to become more 
 abundant in later ages. 
 
 As the Orthoceras has never been met with in the marine Muschel- 
 kalk, much surprise was naturally felt at first when 7 or 8 species of the 
 genus were detected in the Hallstatt beds. Among them are some of 
 large dimensions, associated with large Ammonites with foliated lobes, a 
 form never seen before so low in the series, while the orthoceras had 
 never been seen so high ; although the latter genus has since been met 
 with in the Adnet, or Lower Lias strata of Austria. We can now no 
 longer doubt that, should we hereafter have an opportunity of studying 
 an equally rich marine fauna of the age of the Bunter sandstone or 
 Lower Trias, the great discordance between Paleozoic and Neozoic forms 
 would almost disappear, and the distance in time between the Permian 
 and Triassic eras would be very much lessened in the estimate of every 
 geologist. 
 
 ON THE SUPPOSED EVIDENCE OF PH^ENOGAMOUS PLANTS (NOT GYMNO- 
 SPERMS) IN THE COAL FORMATION (p. 37 1). 
 
 IT has been questioned whether hitherto the botanist has obtained 
 from strata older than the Wealden a single well-determined specimen 
 of any flowering plants except Gymnosperms, such as Conifers and Cy- 
 cads. Hence some imagine that the most highly organized structures 
 of the vegetable kingdom were first created or developed in geological 
 periods comparatively modern, although the antholite of the coal (of 
 which a figure is given at p. 371) was classed by Lindley, so long ago 
 as 1835, as allied to the Bromeliacese. Mr. Charles Bunbury called 
 my attention lately to an antholite in his collection from the Newcastle 
 coal-field, which he compared to Antholyza, an Irideous genus, and on 
 which Dr. Hooker, to whom I have shown it, has sent me the follow- 
 ing remarks. 
 
 "Kew, Feb. 18, 1857. 
 
 "After a careful examination of the beautiful specimen of Antholithes 
 Pitcairnice which you have placed in my hands, I have no hesitation in 
 withdrawing the opinion which I formerly expressed to you (Manual, 
 5th ed., p. 371) of the possible coniferous relation of the genus Antho- 
 lithes. All the specimens I had previously examined were very imper- 
 fect, and suggested to me the possibility of the so-called flowers being 
 tufts of youog leaves like those of the larch. In the specimen now be- 
 fore me, these organs are far more perfect, and confirm (as positively as 
 such materials can) Lindley's idea that Antholithes is the spike of a very 
 
BARRANDE'S " COLONIES" IN 
 
 highly-organized flowering plant in full flower. The specimen, as you 
 are aware, presents no structure ; it is an impression, and therefore I can 
 only judge of its possible affinities from appearances. Now, there is 
 nothing whatever known amongst Cryptogamic plants having the most 
 remote resemblance to this Antholithes, nor amongst Gymnospermous 
 Phsenogams, but there are, both amongst Monocotyledons and Dico- 
 tyledons, genera to which it may plausibly be compared. I allude in 
 the former class to genera of Bromeliacece, Scitaminece, and Orchidece ; 
 in the latter to Laliatce, Lobeliacece, and some others. Upon the whole, 
 the resemblance is strongest to Bromeliacece, amongst which the genus 
 Pitcai'rnia is ranked, and which suggested the specific name to Lindley." 
 Another antholite, apparently of a different species, found by Mr. 
 Prestwich in the coal strata of Coalbrook Dale, and described by Mr. 
 Morris under the name of Antholites anomalus, is figured in the Trans- 
 actions of the Geological Society of London (2d ser., vol. 5, pi. xxxviii. 
 fig. 5). It is quite unlike any thing known in the Gymnospermous or 
 Cryptogamous classes, and greatly resembles, in what is supposed to be 
 the evolution of its floral organs,- the ordinary phsenogamous type. 
 Nevertheless, as both Mr. Robert Brown and Dr. Hooker still regard 
 certain terminal appendages belonging to it as enigmatical, we cannot 
 declare that the affinities of this curious genus are yet made out. 
 
 SILURIAN AND CAMBRIAN ROCKS, AND M. BARRANDE's THEORY 
 OF COLONIES. 
 
 SINCE I alluded in the text (p. 441) to M. Barrande's discoveries in 
 Bohemia, in reference to the Paleozoic rocks, I have enjoyed, during 
 the summer of 1856, the high privilege of visiting in his company the 
 field of his successful labors near Prague, of observing the order and 
 succession of the rocks as interpreted by him, and of inspecting the vast 
 collections which he has accumulated in the course of more than twenty 
 years. These stores are comparable in number and importance rather 
 to the results of a Government survey than to the acquisitions of a pri- 
 vate individual. More than 1500 species of fossil invertebrata, previously 
 unknown, with the exception of a few of the Brachiopoda, and all be- 
 longing to strata older than the Devonian, have rewarded his skilful search. 
 
 M. Barrande has shown, in a recent treatise, that the fauna called by 
 him primordial, a fauna contemporaneous in date with the Cambrian 
 rocks of Great Britain, was also coeval with the fossils of the Alum 
 Schists, and limestones of Sweden, so well described by M. Angelin. 
 In both countries, this fauna, the most ancient yet known, consists 
 almost exclusively of trilobites, scarce any progress having yet been 
 made in bringing to light any mollusca and echinoderms of the same 
 period. Enough, however, has been done to show that distinct natural 
 
SILURIAN ROCKS OF BOHEMIA. 665 
 
 history provinces existed at those very remote times in Scandinavia, 
 Bohemia, England, and the United States. 
 
 Of Trilobites, 27 species have been found in Bohemia in these "pri- 
 mordial" beds, 71 in Scandinavia, 12 in America, and 10 in England, all 
 referable to the same group of genera, but not one in a hundred of the 
 species being common to the different areas. The doctrine of the uni- 
 versality of a primeval fauna, once so popular, is thus completely and 
 forever overthrown. If it still lingers in the minds of some paleontolo- 
 gists, it is probably because of the wide range of certain plants of the 
 carboniferous era. But besides that every day demonstrates this case \o 
 be exceptional, it has also become more and more evident that the appar- 
 ent anomaly is caused partly by the predominance in that ancient flora 
 of ferns and Lycopodiaceae, orders of which the living species are dif 
 fused over as wide a space, and partly by the abundance of plants like 
 the Sigillariae, of which there are no living analogues. There is no 
 proof that the coniferse of the carboniferous era had a more extensive 
 range than the living species of the same class. 
 
 Not only in the earliest known paleozoic epoch has M. Barrande now 
 shown that distinct assemblages of species inhabited separate regions, 
 but also that the same law prevailed in as marked a degree during the 
 times of his second and third faunas, or when rocks of the age .of the 
 Lower and Upper Silurian of England were formed. At these periods, 
 not only peculiar species of Crustaceans, but Cephalopods also, and 
 other mollusks, as well as corals, flourished ; one set in Bohemia, an- 
 other in Scandinavia, and others in the several great regions before 
 enumerated ; in a word, wherever these ancient strata have been care- 
 fully studied. 
 
 But if separate portions of the earth have at every former era been 
 simultaneously peopled by distinct sets of marine species, owing to 
 variations in climate, in the depth of the sea, the mineral nature of its 
 bottom, or by reason of the position of continents and the larger islands, 
 and many other conditions in the organic and inorganic worlds, there 
 must at every former period have been points where distinct zoological 
 provinces were parted from each other by abrupt and narrow barriers, 
 resembling the Isthmus of Suez or the Isthmus of Panama. It is well 
 known that a distinct marine fauna now prevails on each side of those 
 narrow belts of land, and it is evident that a slight subsidence of the 
 earth's crust, to the amount of only a few hundred feet, could cause one 
 host of species to invade the territory of another ; and it might, there- 
 fore, have naturally been asked, whether there are any signs of such 
 invasions having been effected during those reiterated upheavals and 
 subsidences to which geology bears testimony. M. Barrande has fur- 
 nished us with a distinct and satisfactory answer to this question, for he 
 has detected near the upper limits of the Lower Silurian strata of Bohe- 
 mia (in his etage D.) an intercalated and lenticular-shaped mass of fos- 
 siliferous rock, containing organic remains, almost all of them specifi- 
 cally identical with fossils found in the overlying Upper Silurian 
 
666 BARRANDE'S 
 
 deposits. To this intrusive fauna he has given the name of " a colony," 
 a name somewhat ambiguous, perhaps, yet which faithfully expresses 
 one part of his theory, namely, that we have here an exemplification of 
 a contemporaneous fauna, nearly allied to his third fauna E, or the 
 Upper Silurian, which during the deposition of the strata D, obtained 
 for a time a settlement within the Bohemian area, and was afterwards 
 expelled, to reappear, after a lapse of ages, under a slightly altered 
 aspect. The following is a copy of the section by which M. Barrande 
 illustrates this doctrine of colonies, which, so far as relates to the geo- 
 logical sequence and position of the rocks, I have verified on the spot. 
 
 Section through the basin-shaped Silurian Strata of the Centre of 
 
 Bohemia. Barranfe. 
 
 Fig. 7. 
 
 H 
 
 Colony 
 
 D. Lower Silurian, with fossils of the 2d fauna of Barrande, coeval with Llandeilo flags of 
 Murchison. 
 
 d 1 to d 5. Subdivision of the same. 
 E 1. Colony or intercalated beds, with fossils specifically identical, for the most part, with 
 
 those of E 2. 
 E2. -j 
 
 Q > Subdivisions of the Upper Silurian, with fossils of the 3d fauna of Barrande, 
 
 H. j 
 
 t. Trap of contemporaneous origin with E 2, and of which some also occur in the 
 deposit E 1. 
 
 It will be seen that the colony styled E by M. Barrande, but which I shall 
 call E 1, occurs in the midst of the strata d 4, one of the subdivisions 
 of D, so designated by Barrande. The fauna proper to E 1 contains 
 as may as 65 species, five of them peculiar, or not known elsewhere ; 
 two common to the fauna of d 4, in which they are intercalated ; and 
 the remaining 58 common to the base of Barrande's third or Upper 
 Silurian fauna, which I have designated as E 2. 
 
 The late Edward Forbes, when commenting on this doctrine of colo- 
 nies, observed that if accepted it would materially affect the value of 
 the evidence of organic remains, as determining the age and sequence 
 of geological formations, since the proposition involves the introduction 
 of a group of species that experience has shown normally to belong to 
 a later and distinct formation, not merely among and mixed with the 
 fauna of an earlier stage, but amid and separate from that fauna.* Pro- 
 fessor Forbes, therefore, while expressing the highest admiration of M. Bar- 
 rande's talents and labors, questions the accuracy of his geological facts, 
 remarking " that in a disturbed Silurian country where the strata lie at 
 
 c ' Quart. Geol. Journ., 1854, vol. x. p. xxxiv. 
 
SILURIAN ROCKS OF BOHEMIA. 667 
 
 very high angles, and where there are probably convolutions and con- 
 tortions of the beds, there may be such overturns as would cause the 
 appearance of strata containing newer fossils to lie under and amid 
 those containing older ones." But had my late friend visited the neigh- 
 borhood of Prague, he would have learnt that the strata there are not in 
 a state of Alpine confusion, and he would readily have convinced himself 
 that so able an observer as M. Barrande had not been in any way deceived. 
 In fact, the order of superposition is not obscure ; and besides, there is 
 one spot in the suburbs of Prague which I examined, where the inter- 
 calated colonial formation E 1 is reduced in thickness to 6 inches, and 
 where nevertheless it is quite distinguishable by its organic contents, 
 although, as we might have anticipated, there occurs here a slight 
 blending of the distinct faunas, two species of d 4 being associated with 
 a great number of the characteristic fossils of E 1. 
 
 How, then, are we to explain the phenomena ? The facts themselves 
 seem to have been very generally misunderstood, partly, perhaps, in con- 
 sequence of the use of the term " colony ;" partly for want of distinct 
 names for the two periods, or subdivisions of time, E 1 and E 2. The 
 facts, indeed, themselves are by no means simple, since they relate, first, 
 to the alternate colonization of a certain area by two distinct nations of 
 species; secondly, to a continual change of character undergone by 
 each of the contemporaneous nations, in consequence of the dying out 
 of old species and the births or first appearances of new ones. M. Bar- 
 rande has been treated very much as an antiquary would be should he 
 pretend to have found monumental evidence of an Anglo-Saxon colony 
 established on Roman ground in the days of the Emperor Justinian ; 
 whereas, there is really no such anachronism in the paleontological 
 facts, as exhibited in Bohemia, and as described by the author of the 
 " Colonial" theory. He simply tells us, in regard to the colony E 1, 
 that out of 63 species, 5 are peculiar to it where it is in its full 
 strength, in other words, there is a difference between the species of 
 E 1 and pf E 2, amounting to about 8 or 9 per cent., indicating a change of 
 no less than one-twelfth of the whole fauna in the interval between E 1 
 and E 2, to say nothing of such discordance as would certainly be found 
 to exist when the rarity of particular species of the first period came to 
 be contrasted with their abundance in E 2, and vice versa. 
 
 Before a geologist is entitled to regard this case as abnormal, or not 
 in harmony with the laws known to have governed the fluctuations of 
 the organic world in bygone ages, he must show that the fauna called 
 D underwent much greater alterations than did the fauna of the mother- 
 country of E 1 and E 2 in the interval of time between the deposit E 1 
 and that called E 2, -in other words, he ought to show that more than 
 a twelfth of the species of D died out, and more than 8 or 9 in 100 of 
 new species came in, in the interval separating d 4 and d 5. Now, so 
 far as I have learnt from M. Barrande, no details have as yet been ascer- 
 tained respecting the fossils of these two subdivisions sufficiently minute 
 to entitle any one to infer that the rate of fluctuation of the two faunas, 
 
668 ANTIQUITY OF FOSSIL BIRDS. 
 
 within the period alluded to, was very unequal. In the course of the 
 interval between E 1 and E 2, strata of micaceous shale and sandstone 
 of the system D, more than 3,000 feet thick, were deposited ; and dur- 
 ing the accumulation of this immense mass of rock some species dis- 
 appeared, while many survived and are common to d 4 and d 5 ; other 
 fossils being peculiar to each of those subdivisions respectively. 
 
 Trap rocks accompany the " Colonial beds" E 1, and are decidedly 
 of contemporaneous origin. Occasionally an orthoceras may be seen 
 involved in the greenstone, while pebbles and angular fragments of trap 
 are intermixed with the fossils of the colony. 
 
 Again, there are other intrusions of similar igneous rocks at the base 
 of E 2, and M. Barrande with good reason appeals to these volcanic 
 appearances as lending support to his hypothesis of former changes of 
 level, by which a barrier of land may have been lowered for a time so 
 as to allow currents of salt-water flowing from the northeast to intro- 
 duce the fauna E 1 into the region previously occupied by D ; and a 
 recurrence, he remarks, of similar oscillations may afterwards have 
 caused the retreat of the colonists, as well as the subsequent return of 
 most of them when the fauna E 2 obtained its permanent footing in 
 Bohemia. Warm currents, like the Gulf Stream, pouring into a colder 
 sea, might carry with them a whole assemblage of species fitted for a 
 more elevated temperature, and capable of superseding the natives of a 
 colder sea, while colder currents invading a warmer sea might give rise 
 to analogous phenomena. In each case along the edges of the space 
 thus colonized, some members of the old native fauna might maintain 
 their ground against the new-comers ; and this may explain why, when 
 the deposit E 1 thins out to a few inches, some species of D are inter- 
 mingled with those of E 1. 
 
 It may be useful to add that in E 2 (a calcareous formation only 500 
 feet in thickness), no less than 900 species of fossil invertebrata have 
 been found by M. Barrande. This set of strata passes upwards into F, 
 and this again into G, and G into H, each having, at the point, of con- 
 tact, so many species in common, that M. Barrande has thought it 
 necessary to regard the whole as one system ; yet such is the aggregate 
 result of continual changes, that when the two extremes of the series 
 are contrasted, there is only 1 per cent, common to E 2 and H. 
 
 Many important conclusions will follow if we admit the accuracy of 
 the facts and reasonings above set forth. M. Barrande has himself 
 remarked, that, before his discoveries were made, a geologist, finding in 
 some part of Europe to the northeast of Prague, rocks characterized by 
 the fossils of E 1, would certainly have regarded them as Upper Silu- 
 rian, instead of assigning them to their true era, viz. that of D or the 
 Lower Silurian. On the other hand, if the fauna D, after it was locally 
 exterminated in the region of Prague, still continued to flourish else- 
 where under a slightly modified form which might, in accordance with 
 M. Barrande's nomenclature, be styled d 6 such a fauna might cer- 
 tainly be mistaken for one of Lower Silurian date, although, in truth, 
 
ANTIQUITY OF FOSSIL BIRDS. 669 
 
 contemporaneous with strata generally classed by geologists as Upper 
 Silurian. 
 
 The imagination may well take alarm at the confusion which we may 
 expect to encounter in settling sundry questions of Geological chronol- 
 ogy, when we have to deal with ancient deposits found on the frontiers 
 of distinct Natural History provinces. But it is consolatory to reflect 
 that all this ambiguity will arise out of the strict agreement prevailing 
 between the present and ancient condition of the globe, and the laws 
 governing the changes of its surface, whether they be those of the ani- 
 mate or inanimate world. So long as we feel sure that in existing na- 
 ture we have a key for interpreting the mysteries of the past, we need 
 never despair ; whereas, had the causes acting in the remoter ages differ- 
 ed either in -kind or degree from those now operating, our science must 
 forever have continued one of mere conjecture and ingenious speculation. 
 
 ANTIQUITY OF FOSSIL BIRDS (p. 456). 
 
 SINCE the table printed at p. 456 was compiled (in 1854), the records 
 of this great class of Vertebrata can be carried back somewhat farther 
 in time, or one step lower down in the Tertiary series. Early in 1855 
 the tibia and femur of a large bird equalling at least the ostrich in size 
 were found at Meudon near Paris, at the base of the Plastic clay. This 
 bird, to which the name of Gastornis Parisiensis has been assigned, ap- 
 pears, from the Memoirs of MM. Hebert, Lartet, and Owen, to belong to 
 an extinct genus. Professor Owen refers it to the class of wading land- 
 birds rather than to an aquatic species.* 
 
 That a formation so much explored for economical purposes as the 
 Argile Plastique around Paris, and the clays and sands of corresponding 
 age near London, should never have afforded any vestige of a feathered 
 biped previously to the year 1855, shows what diligent search and what 
 skill in osteological interpretation are required before the existence of 
 birds of remote ages can be proved by more decisive evidence than their 
 supposed foot-prints. 
 
 * Quart. Geol. Journ., vol. xii. p. 204, 1856. 
 
INDEX. 
 
 [The Fossils, the names of which are printed in Italics, are figured in the volume.] 
 
 ABICH, M., on trachytic rocks, 467. 
 Aerodus noMlis, tooth of, 321. 
 Acrolepis Sedgwickii, scale of; 854. 
 Actceon aeutus, great oolite, 308. 
 Actinolite-schist, 590. 
 ^Echmodiis, scales and outline of, 321. 
 ^Egean Sea, mud of, 35. 
 
 , animal life in depths of, 136. 
 
 ^lEpiornis of Madagascar, 343. 
 
 Agglomerate, volcanic rock, 4T1, 472. 
 
 Agnostus integer, A. rex, 450. 
 
 Agassiz, M., cited, 87, 217, 321, 349, 396, 415, 418. 
 
 , on fossil fishes of molasse and faluns, 170. 
 
 , on fossil fish of lias, 320. 
 
 , on fossil fish in Permian marl-slate, 353. 
 
 , on fish from Sheppey, 217. 
 
 , on footprints, 348. 
 
 , on fishes of brown-coal, 540. 
 
 , on glaciers, 146, 149. 
 
 Age, test of, by fragments of older rock, 101. 
 of metamorphic rocks, 611. 
 
 , test of, in plutonic rocks, 573. 
 
 , of Spanish volcanoes, 536. 
 
 , of volcanic rocks, how tested, 519, 522. 
 Air-breathers in coal, rarity of, 401. 
 Aix-la-Chapelle, hot springs at, 573. 
 Alabama, cretaceous shingle of, 255. 
 Alabaster defined, 13. 
 Alberti on the Keuper, 333. 
 Alexander, Capt, marine sheila in crag found 
 
 by, 155. 
 
 Alluvium, term explained, 79. 
 . . . ., formation of, 81. 
 
 in Auvergnc, 80. 
 
 Alpine blocks on the Jura, 148. 
 
 erratics, 146. 
 
 Alps, curved strata of, 58. 
 ...., elevated fossiliferous rocks in, 4. 
 ...., nummulitic formation of, 230. 
 . . . ., of Switzerland, 613. 
 
 , Swiss and Savoy, cleavage of, 601. 
 
 Altered rocks, 479. 
 
 .... by subterranean gases, 595. 
 
 Alternations of rocks, 14 
 
 .... of marine and freshwater formations, 32. 
 
 Alum-schists, Silurian, of Sweden, 451. 
 
 Alumine in rocks, 11. 
 
 Amllyrhynchm cristatus (recent) 325. 
 
 America, North, Lithodomi in beaches of, 78. 
 
 . . . ., South, cretaceous strata, 255. 
 
 , South, fossils of, 163. 
 
 ...., South, gradual rise of parts of, 46. 
 Ammonites oifrons, A.Nodotianugyt, A.stri- 
 atulus, A. Walcottii, 319; A. Eraiken- 
 ridgii, A. margaritatus, A. Stokesii, A. 
 Ktriatidus, 316; A. Elizabeths, A. Jason, 
 304 ; A. Humphresianus, 315 ; A. Rhotoma- 
 gensis, 251. 
 
 Ampelite, or aluminous slate, 590. 
 Amphibole, 465. 
 
 Amphibolite, or hornblende rock, 472, 590. 
 Amphisterjina Ilauerina, eocene, 179. 
 
 Amphi&terium Eroderipii, jaw o 811. 
 
 .... Prevostii, jaw of, 311. 
 
 Amputtaria gutuca (recent), 30. 
 
 Amsterdam, or St Paul Island, 508. 
 
 Amygdaloid, 463. 
 
 Ananchytea ovatus, chalk, 243. 
 
 Ancittaria subulata, eocene, 31. 
 
 Ancyloceras gigas, 258 ; A. spintgerum, 251, 
 
 Ancylm elegans, pleistocene, 29. 
 
 Andolys, chalk-cliffs at, 268. 
 
 Andernach, strata near, 540. 
 
 Andes, plntonic rocks of, 577. 
 
 , rocks drifted from, to Chiloe, 150. 
 
 Andesite, 467. 
 
 Anodonta CordieriL A. latimarginatus (re- 
 cent), 28. 
 
 Anoplotherium commune, tooth of; 210. 
 
 .... gracile, outline of, 225. 
 
 Anthophyttum lineatum, 182. 
 
 AntholitTies, coal, 371. 
 
 Anthracite in Ehode Island, 597. 
 
 Anticlinal line, 43, 57. 
 
 Antrim basalt, age of, 180. ' 
 
 rocks altered by dikes in, 480. 
 
 Antwerp, strata like Suffolk crag near, 173. 
 
 Apateon pedestris, a carboniferous reptile, 396. 
 
 Aphanite, or cornean, 472. 
 
 Apennines, limestone in, 478. 
 
 Appalachian coal-field, 389. 
 
 Appalachians, altered rocks in, 596. 
 
 Apiocrinites rotundus, oolite, 806. 
 
 Aptychus latus, oolite, 802. 
 
 Apteryx in New Zealand, 164. 
 
 Apus f dubius, coal, 3S5. 
 
 Aqueous rocks defined, 2. 
 
 .... rocks, mineral character of, 97. 
 
 deposits, superposition of, 96. 
 
 Aralo-Caspian formations, 175. 
 
 Arbroath paving-stone, 415. 
 
 . . . ., section from, to the Grampians, 48. 
 
 Archegosauru* medium, skin of; A. minor, 
 coal-measures, 397. 
 
 Archiac, M. d', cited, 149. 
 
 , on fossils in chalk, 251. 
 
 .on shells in French lower eocene, 228. 
 
 Ardeche, lava in, 484 
 
 Arenaceous rocks described, 11. 
 
 Argillaceous rocks, 11. 
 
 ....schist, 589. 
 
 Argile plastique, or lower eocene, 229. 
 
 Argyleshire, trap-vein in cliff, 477. 
 
 Argyll, Duke of, on Isle of Mull tertiaries, 179. 
 
 Arkose, 590. 
 
 Arran, age of granite in, 583. 
 
 section of, 585. 
 
 Arran, dike of greenstone in, 477. 
 
 Arrangement ot fossils in strata, 5, 21. 
 
 Arthur's Seat, altered strata of, 481. 
 
 Arvicola, tooth of, 167. 
 
 Asaphus tyrannus, lower Silurian, 440. 
 
 Aspidura loricata, Permian, 334. 
 
 Astarte bipartita, A. Omalii, 171. 
 
672 
 
 INDEX. 
 
 Astarte borealis, 130 ; A. Zaurentiana, 140. 
 
 Asterophyllitesfoliosa, coal, 366. 
 
 Aatrangia lineata, 182. 
 
 Astropecten o'ispatus, eocene, 218. 
 
 Athyris namcula, Ayraestry, 431. 
 
 Ashby-de-la-Zouch, fault in coal-field of, 69. 
 
 Ascension, lamination of volcanic rocks in, 606. 
 
 Asti, formations at, 174 
 
 Atberfield, cretaceous strata of, 257. 
 
 Atrium of a volcano, 502. 
 
 Atrypa reticularis, Aymestry, 434. 
 
 Atwria ziczac. London clay, 218. 
 
 Augite, 466. 
 
 Aulopora serpens, Devonian, 422. 
 
 Auricula (recent), 218. 
 
 Aurillac, freshwater strata of, 204. 
 
 Austen, Mr. E. A. G., en phosphate of lime, 251. 
 
 . . . ., on upper greensand, 250. 
 
 Australia, auriferous gravel of, 630. 
 
 , cave-breccias of, 161. 
 
 .'..., extinct mammals in auriferous gravel of, 
 
 630. 
 
 Auvergne, freshwater formations, 202. 
 . . . ., succession of changes in, 196. 
 
 , lacustrine strata, 199. 
 
 ...., mineral veins of, 624. 
 
 ...., indusial limestone of, 201. 
 
 . . . ., extinct volcanoes of, 545. 
 
 . . . ., alluvium in, 80. 
 
 Aveline, Mr., on Caradoc sandstone, 438. 
 
 Amcula cygnipes, A. incequivalvis, 317. 
 
 .... papyracea, 886 ; A. socialis, 334. 
 
 Aviculopecten sublobatus, carboniferous, 406. 
 
 Axinus angulatus, London clay, 218. 
 
 Aymestry limestone, 433. 
 
 BACILLARIA, fossil in tripoli, 25. 
 
 .... vulgaris ?, in tripoli, 25. 
 
 Baculites anceps, B. faujassii, 245. 
 
 Bagshot sands, 214. 
 
 Bahia Blanca, fossil remains at, 154 
 
 Baise, Bay of, strata in, 525. 
 
 Bakewell, Mr., on cleavage in the Alps, 601. 
 
 Bala, lower Silurian rocks at, 441. 
 
 Balcena emarffinata, tympanic bone of, 173. 
 
 Balgray, near Glasgow, stumps of trees in coal, 
 
 Baltic, brackish water strata on coast of, 119. 
 
 Barrande, M., on Bohemian Silurian rocks, 441. 
 
 , on primordial fauna, 443. 
 
 , on trilobites, 441. 
 
 Barton clay described, 212. 
 
 Barcombe, chalk-flint gravel near, 286. 
 
 Basilosaurus cetoides, 233. 
 
 Basterot, M. de, on tertiaries of south of France, 
 110. 
 
 Basalt, 6, 466. 
 
 . . . ., columnar, in the Eifel, 485. 
 
 , columnar, near Vicenza, 484. 
 
 . . . ., columnar, of Giants' Causeway, 6. 
 
 ...., columnar, structure of, 483. 
 
 Basset, term explained, 56. 
 
 Batrachian, eggs of?, in old red, Scotland, 417. 
 
 Sate, teeth of, 219. 
 
 Bayfleld, Capt., on fossil shells in Canada, 133. 
 
 , on inland cliffs in Gulf of St. Lawrence, 78. 
 
 Bean, Mr., on Norwich crag shells in York- 
 shire, 155. 
 
 on fossil shells from oolite, 314. 
 
 Beachy Head, chalk-cliffs near, 275. 
 
 Beaumont, M. E. de, on rocks of Hautes Alpcs, 
 
 . . . ., on lamination of volcanic rocks, 476. 
 
 , on pisolitic limestone, 236. 
 
 ..., on Swiss Alps, 579. 
 ...., on quartz, 68. 
 . . . ., on oolite formation in France, 252. 
 
 , on Wealden island, 281. 
 
 Beck, Dr., cited, 201, 242. 
 
 . , . ., on graptolites, 441. 
 
 Belemnites hastatus, 804 ; B. mucronatus, 245. 
 
 .... Puzosianus, Oxford clay, 305. 
 
 Bellerophon costatus, carboniferous, 407. 
 
 Belosepia sepioidea, eocene, 218. 
 
 Bembridge or Binstead beds, Islo of "Wight, 
 
 193, 208. 
 
 Berenicea, diluviana, oolite, 307. 
 Berger, Dr., on rocks altered by dikes, 480 
 Bergmann on trap, 460. 
 Berlin, tertiary strata near, 189. 
 Bermuda Islands, lagoons in, 240. 
 
 , rocks of, 78. 
 
 Bernese Alps, gneiss in, 614 
 
 Berthier, M., on augite and hornblende, 464 
 
 Beudant, M., on Hungary, 544. 
 
 Beyrich, M., on Berlin tertiaries, 189. 
 
 , on North German tertiaries, 178. 
 
 Biaritz, calcareous cliffs of, 72. 
 Bilin tripoli, composed of Infusoria, 25. 
 Binney, Mr., on Stigmaria and Sigillaria, 367. 
 Bird, bone of, in lower eocene beds, 458. 
 ...., footprints of, 346. 
 
 , fossil, scarcity of, 458. 
 
 Bischoff, Prof., experiments on heat, 594. 
 
 , on steam at a high temperature, 595. 
 
 Blackdown beds, equivalent of gault, 251. 
 
 Blainville, on number of genera of mollusca, 28. 
 
 Boase, Dr., cited, 598. 
 
 Boblaye, M., on inland cliffs, 73. 
 
 ...., cited, 555. 
 
 Bog-iron-ore, 26. 
 
 Bohemia, Silurian rocks of, 450. 
 
 Bolderberg, in Belgium, miocene or falunian 
 
 strata of, 178. 
 
 Bone-bed offish-remains in Armagh, 409. 
 ...., Silurian, 431. 
 
 Bone-beds, usually contain rolled bones, 454. 
 Boom and Eupelmonde, 188. 
 Bordeaux, falunian strata near, 178. 
 ...., tertiary deposits of, 178. 
 Borrowdale, black-lead of, 38. 
 Bosquet, M., on Kleyn Spawen tertiary shells, 
 
 134. 
 
 . . . ., on Maestricht beds, 237. 
 Bos taurus, tooth of, 166. 
 Boston, U. S., recent strata in morass, upraised 
 
 and bent, 135. 
 
 Bothnia, Gulf of, land upheaved, 45. 
 Boue, M., on arrangement of rocks, 95. 
 
 , on fossil shells in Hungary, 545. 
 
 . . . ., on Carrara marble, 612. 
 
 , on Swiss Alps, 614 
 
 Bonelli, on strata in Italy, 111. 
 Boulder formation in Canada, 139. 
 ...., mineral ingredients of, 131. 
 .... in England, 126, 186. 
 . . . ., period, fauna of, 131. 
 Boulders, 128. 
 
 striated, 142. 
 
 Boutigny, M., cited, 565. 
 
 Brown, Lieut. A., E. N., drawings of rocks in 
 
 Gulf of St Lawrence, 78. 
 Bowerbank, Mr., on fossil flora of Sheppey, 216. 
 Bowman, Mr., on coal-seams, 391. 
 Bracklesham Bay, characteristic shells of, 214. 
 Bradford encririites, 307. 
 Brash, term, explained, 81. 
 Bravard, M., on Auvergne mammalia, 203, 421. 
 Brazil, ossiferous caves in, 164. 
 Breccia on ancient coast-lines, 73. 
 Brickenden, Captain, on Elgin fossils, 413. 
 Brighton, elephant-bed of, 287. 
 Bristol, dolomitic conglomerate near, 353. 
 
 , section of strata near, 102. 
 
 Brocchi, on Subapennines, 110, 173. 
 Brockedon, Mr., on black-lead, 38. 
 Broderip, Mr., cited, 312. 
 Brodie, Eev. P. B., on fossil insects, 300, 327. 
 . . ., Mr. W. E., Purbeck inammifer found by, 
 295. 
 
 Bromley, oyster-bed near, 220. 
 Brcngniart, M. Adolphe, on Eocene flora, 216. 
 . . . ., on flora of cretaceous period, 265. 
 
 , on fossil plants in lias, 328. 
 
 ...., on plants of bunter-sandstein, 335. 
 ...., on fossil fir-cones, 363. 
 ...., on Permian flora, 357. 
 , on Sigillaria, 366. 
 
INDEX. 
 
 673 
 
 Brongniart, M. Adolphe, on asterophylites, 366. 
 
 on stigmaria, 367. 
 
 , on age of acrogens, 871. 
 
 Brongniart, M. Alex., on Paris tertiaries, 109. 
 
 , on eocene formation, 222. 
 
 , on shells of numirmlitic formation, 230. 
 
 , on coal-mine near Lyons, 373. 
 
 B'-ontesflabelli/er, Devonian, 424. 
 
 Brora, oolitic coal-formation, 314 
 
 , granite near, 582. 
 
 Brown-coal of Germany, age of, 180. 191. 
 
 Brown, Mr. Richard, on stigmariae, 367. 
 
 , on coal-formation, 367. 
 
 , on Cape Breton coal-field, 380. 
 
 , on carboniferous rain-prints, 381. 
 
 Buch, Von. See Von Buch. 
 
 Buckland, Dr., on cave at Kirkdale, 160. 
 
 , on coal plants, 372. 
 
 , on coprolites in chalk, 241. 
 
 , on fish of lias, 321. 
 
 , on glaciers in Caernarvonshire, 136. 
 
 ...., on oyster-bed near Bromley, 220. 
 
 , on parallel roads, 87. 
 
 , on term Poikilitic, 332. 
 
 . . . ., on sanrians of lias, 323. 
 
 ..... on sudden destruction of saurians, 334. 
 
 . . . ., cited, 161, 292, 296. 308, 309. 
 Buddie, Mr., on creeps in coal-mines, 50. 
 
 , on ancient river-channels of coal-period, 
 
 395. 
 
 Buist, Dr. G., on saltness of Red Sea, 345. 
 JBulinius ellipticns, 209 ; B. lubricu.*, 30. 
 Bunbury, Mr. C. J. F , on plants of oolitic coal- 
 field, 331 ; on fossil plants in Madeira, 515. 
 Bunsen, Prof., on palagonite, 470. 
 Bunter-sandstein, 335. 
 Euprestis f elytron of, in oolite, 308. 
 Burmeister, on trilobites, 441. 
 Burnes, Sir A., cited, 344 
 
 CAIRO, excavations at, 3. 
 
 Calamite* cannceformis, C. Snckowii, 364. 
 
 Calamites near Pictou, 375. 
 
 Catamite, root-end of, 364 ; structure of, 365. 
 
 Calamophyllia radiata, oolite, 305. 
 
 Calamodendron, 365. 
 
 Calcaire grossier, 226. 
 
 siliceux, 225. 
 
 Calcareous rocks, 12. 
 Calcarina rarizpina. eocene, 227. 
 Calcfola sandalina, Devonian, 424. 
 Caldcleugh. Mr., cited, 521. 
 Caldera of Palma, 494 to 508. 
 California, auriferous gravel of, 629. 
 Calymene Blumenbachii, Wenlock, 436. 
 Cambrian group, 447. 
 
 , lowest fossiliferous beds of, 449. 
 
 rocks of Sweden, 451. 
 
 rocks of United States, 451. 
 
 volcanic rocks, 559. 
 
 Campagna di Roma, tuffs of, 530. 
 Campdphyllum Jlexuosum, Devonian, 403. 
 Canada, shells in drift of, 139. 
 Cantal, freshwater formation of, 204, 553. 
 
 , igneous rocks of, 552. 
 
 C-pe Breton, coal-measures of, 380. 
 
 Cape Wrath, granite-veins in, 568. 
 
 Caradoc sandstone, 437. 
 
 Carbonaceous shale, 812. 
 
 Carbonate of lime scarce in metamorphic rocks, 
 
 in rocks, how tested, 12. 
 
 Carboniferous group, 35S. 
 .... flora, 360, 370. 
 
 limestone of North America, 410. 
 
 .... period, plutonic rocks of, 580. 
 .... period, volcanic rocks of, 556. 
 
 reptiles, 396. 
 
 C&rcharodon heterodon, tooth of, 215. 
 Cardiocarpon Ottonis, Permian, 356. 
 Cardita glolona, 213 ; C. planicosta, 214. 
 Cardium porulovum, eocene. 228. 
 Cardium dissimile. C. strlaiulum. 300. 
 Carne, Mr., on Cornish lodes, 621, 622. 
 
 43 
 
 Carrara marble, 591, 612. 
 
 Caryophyllia cce&pitosa, bed of, in Sicily, 157 
 
 Castrogiovanni, bent strata near, 58. 
 
 Catalonia, volcanic region of, 531. 
 
 Catenopora eschar oides, Wenlock, 435. 
 
 CatMus Lamarckii, chalk, 247. 
 
 Canlopteris primceva, coal, 361. 
 
 Cautley, Sir Proby, on Sewalik hills, 182. 
 
 Caves in Europe, 160. 
 
 .... at Kirkdale, 160. 
 
 .... in Sicily, 159. 
 
 in Australia, 161. 
 
 Central France, Upper Eocene of, 194. 
 
 Cephalaspes Lyellii, old red 4 415. 
 
 Cercitites nodosus, triassic, 334 
 
 Cerithium cinctum, 30; C. concatum^ 211. 
 
 flegans, C. plicatum, 193 ; C. melanoide* 
 
 220. 
 
 Cervus alcts, tootn of, 166. 
 
 Cestracion PhUlippi (recent), jaw of, 249. 
 
 Chalk, or cretaceous beds, 236. 
 
 , pinnacle of, near Sherringham, 134. 
 
 of Faxoe, 238. 
 
 , .., white, fossils of, 26, 245. 
 
 , .., white, section of, 239. 
 
 , . ., white, extent and origin of, 240. 
 
 , white, animal origin of, 241. 
 
 .....pebbles in, 241. 
 
 , difference of, in North and South Europe, 
 
 252. 
 
 cliffs, inland, on Seine, 268. 
 
 , needles of, in Normandy, 269. 
 
 flints, bed of, near Barcombe, 2S6. 
 
 Chama squamosa, eocene, 212. 
 Chambers, Mr., on Glen Roy, 88. 
 Chamisso, cited, 242. 
 
 Chara elaxtlca (recent), C. medicaginukt,32, 
 
 C. tuberculata, 209. 
 Chara, in freshwater strata, 81. 
 
 , in flints of Cantal, 2d5. 
 
 , in Eocene strata of France, 194. 
 
 , in Purbeck beds, 295. 
 
 Charlesworth, Mr. E., on Crag, 16S. 
 
 , on Stonesfield rnammifer, 457. 
 
 Charpentier, M., on Alpine glaciers, 146, 149.. 
 Chtirvtherium, footprints of, 337, 397. 
 Chelonidn, footsteps of, 413. 
 Chemical and mechanical deposits, 33. 
 Chiastolite-slate, 590. 
 Chili, earthquake in, 61. 
 
 , gold-mines in, 468. 
 
 Chiloe, rocks drifted from Andes to, 150. 
 Chimcera monstrosa (recent), 322. 
 Chlorite-schisr, 8, 5S9. 
 Christiania, dike near, 479. 
 
 , passage of granite into trap-rocks at, 564. 
 
 . . . ., granite near, 570. 
 
 , gneiss near, 570. 
 
 , intrusion of granite into beds near, 570. 
 
 Chronological groups, 102. 
 
 table of fossiliferous strata, 104. 
 
 Cidaris corona ta, coral-rag, 303. 
 Cinder-bed, Purbeck, 293. 
 Cladocora steUaria, pliocene, 157. 
 Classification of rocks and strata, 2, 10, 104. 
 Claiborne, marine shells of, 232. 
 Clausen, Mr., on Brazil caves, 164. 
 Clausilia biden#, Rhine valley, 30. 
 Clavulina corrugata, eocene, 227. 
 Clay, defined, 11. 
 Clay-slate, 8, 589. 
 Clay-ironstone, 886. 
 Clays, plastic, 219. 
 Cleavage of rocks, 601, 604. 
 Climate of drift-period, 145. 
 
 of coal -period, 395. 
 
 Clinkstone, or phonolite, 472. 
 
 Clinton group, Silurian, United States, 445. 
 
 Clyiiifn ia linearis, Devonian, 421. 
 
 Coal, at Brownsville, Pennsylvania, viow of, 39& 
 
 , conversion of lignite, into 394. 
 
 . . . ., how formed, 372. 
 
 , insects in, 335. 
 
 measures, 353, 359. 
 
674 
 
 INDEX. 
 
 Coal mine, near Lyons, 374 
 
 , Nova Scotia, time required for its growth 
 
 383. 
 
 , oolitic at Brora, 314. 
 
 period, climate of, 395. 
 
 pipes, danger of, 8T3. 
 
 seams, continuity of, 394. 
 
 strata, footprints of reptiles in, 397. 
 
 .*..., zigzag flexures of, near Mons, 53. 
 Coal-field at Burdiehouse, 886. 
 
 , oolitic, of Kichmond, Virginia, 330. 
 
 of Ashby-de-la-Zouch, 69. 
 
 .... of Yorkshire, fossils of, 386. 
 
 United States, diagram of, 388. 
 
 Coalbrook Dale, beetles in coal of, 385. 
 
 , fossil cones in, 363. 
 
 . .., coal-measures of, S85. 
 
 faults in, 62. 
 
 Cochlioduft contoptus, teeth of, 409. 
 Cockfield Fell, rocks altered by dikes, 481. 
 Gcelacantktts granulatus, scale of, 354. 
 CodorJiynchua, sword of, 215. 
 Colchester, Mr., on mammalia at Kyson, 219. 
 Color in shells of mountain-limestone, 406. 
 Columbia, Vinegar Kiver of, 224. 
 Come, ravine in lava of, 550. 
 Concretionary structure, 87. 
 Condensation of rock-material, 38. 
 Gone of a pine, Purbeck, 300. 
 Cones in Val di Noto, 488. 
 
 and craters, 461. 
 
 .... and craters, absence of, in England, 6. 
 Conglomerate, or pudding-stone, 11, 47. 
 .... dolomitic, 354. 
 Coniferous trees, fossil, 368. 
 Connecticut, valley of the, 346. 
 
 beds, antiquity of, 349. 
 
 Conrad, Mr., on cretaceous rocks, 255. 
 Consolidation of strata, 33. 
 Vonocephalus striatus, Cambrian, 450. 
 Conularia ornata, Devonian, 423. 
 Conus deperditus, eocene, 216. 
 Conybeare, Mr., cited, 64, 69, 273, 318. 
 
 , on Plesiosaurus, 321. 
 
 ...., on oolite and lias, 329. 
 . . . ., on term Poikilitic, 332. 
 
 on crocodiles, 217. 
 
 Cook, Capt, on Fucus giganteus, 242. 
 Coprolites in chalk, 241. 
 Coralline Crag, fossils in, 170. 
 Coral islands and reefs, 34, 46. 
 
 rag of oolite, 302. 
 
 Corals, Devonian, geographical distribution of, 
 428. 
 
 of Devonian system, 422. 
 
 Corals of Devonian strata in United States, 427. 
 
 in Wenlock formation, 435. 
 
 Corals, neozoic type of, 403. 
 
 Gorbula alata, Purbeck, 263. 
 
 pisum, eocene, 193. 
 
 Corinth, corrosion of rocks by gases near, 595. 
 
 Cornbrash of lowr oolite, 805. 
 
 Cornean, or aphanite, 472. 
 
 Cornwall, clay in, 12; granite-veins in, 569, 593. 
 
 , mineral-veins in, 620, 622. 
 
 , tin of, newer than Irish copper, 628. 
 
 Cotta, Dr. B., on granite in Saxony, 583. 
 Crag, coralline, fossils in, 170. 
 
 , comparison of faluns and, 177. 
 
 . . . ., fluvio-marine, Norwich, 154 
 
 Crags of Suffolk, red and coralline, 110, 168. 
 
 Craigleith fossil trees, 40. 
 
 quarry, slanting tree in, 376. 
 
 Crania, attached to Echinus, 23. 
 
 Parisiensis, chalk, 246. 
 
 Crassatella sulcata, eocene, 213. 
 Craw.no, Omalii, coralline crag, 171. 
 (rater of Island of St. Paul, 509. 
 Creeps in coal-mines described, 52. 
 ( Iredneria in quadorsandstein, 266: 
 Cretaceous rocks of Pyrenees, 579. 
 .... group, 234 
 .... group, flora of, 265. 
 
 Cretaceous strata in South America and India, 
 255. 
 
 period, plutonic rocks of, 579. 
 
 .... volcanic rocks, 555. 
 
 rocks in United States, 254. 
 
 ...., lower, 256. 
 
 Crinoids, Silurian, 436. 
 
 Cristellaria rotulata, chalk, 26. 
 
 Crocodiles near Cuba, 325. 
 
 Croizet, M., on Auvergne fossil mammalia, 203. 
 
 Cromer, contorted drift near, 134 
 
 Crop out, term explained, 55. 
 
 Crust of earth defined, 2. 
 
 Crystalline limestone, 351. 
 
 rocks, erroneously termed primitive, 9. 
 
 rocks, foliation of, 606. 
 
 schists defined, 7. 
 
 Curral, valley in Madeira, how formed, 516. 
 
 Curved strata, 47, 49, 135. 
 
 Cutch, Runn of, 844 
 
 Cuvier, M., on eocene formation, 222. 
 
 , on Amphitherium, 311. 
 
 . . . ., on tertiary strata near Paris, 109. 
 
 , on fossils of Montmartre, 223, 224. 
 
 Cyathea glauca (recent), 863. 
 Cyathina Eowerbankii, gault, 403. 
 Cyathocrinites planus, carboniferous, 405. 
 Oyathocrinus caryocrinoides, 405. 
 Cyathophyllum flexuosum, 403 ; C. coespito- 
 
 sum, 422 ; C. turbinatum, 435. 
 Cycadeoidea megalophylla, Purbeck, 296. 
 Gycadites comptus, oolite, 314. 
 Cyclas amnicd, 132 ; C. obovata, 28. 
 Cyclopteris Hibernica, Devonian, 414. 
 Cyclopian Islands in Sicily, 523. 
 Cyclostoma elegans, pleistocene, 30. 
 Cylindrites acutus, oolite, 308. 
 Cyprcea coccinelloides, red crag, 1 70. 
 Cyprides, Lower Purbecks, 296"; Middle Pur- 
 becks, 294; Upper Purbecks, 291 ; Wealden, 
 262. 
 
 Cypridina serrato-striata, Devonian, 421. 
 Cypris t inflata, coal, 384 
 Cypris in Lias, 327. 
 .... in Wealden, 262. 
 
 in marl of Anvergne, 199. 
 
 .... in Purbeck beds, 293, 294, 296. 
 
 Cyrena consobrina, 28 ; C. cuneiformis, 220 ; 
 
 G. semistriata^ 193. 
 Cystideae in Silurian rocks, 440. 
 Cytheretya, chalk, 26. 
 
 DADOXYLON, coal-plant, 369. 
 
 Dana, Mr., on crystalline limestone, 597. 
 
 , on coral-reef in Sandwich Islands, 241. 
 
 , on volcanoes of Sandwich Islands, 489, 
 
 493, 546. 
 
 Dapedius monilifer, scales of, 321. 
 Daphnogene cinnamomifolia, 191. 
 Dartmoor, granite of. 5SO. 
 Darwin, Mr., on foliation, 606. 
 
 , cited, 241, 242. 
 
 . . . ., on boulders and glaciers in S. America, 142, 
 
 . . ., on cleavage in South America, 606. 
 , on coral-islands of Pacific, 241. 
 
 ..., on dike in Bt Helena, 528. 
 
 , on habits of ostrich, 349. 
 
 , on fossils in South America, 154. 
 
 . . ., on Fucus giganteus, 242. 
 
 . . ., on gradual rise of part of S. America, 46. 
 
 . . . , on lamination of volcanic rocks, 609. 
 
 . . ., on parallel roads, 87, 88. 
 
 . . ., on plutonic rocks of Andes, 577. 
 
 . . ., on recent strata near Lima, 120. 
 
 , . ., on saurians in Galapagos Islands, 325. 
 
 . . ., on sinking of coral-reefs, 46. 
 
 ..., on Welsh glaciers, 136. 
 Daubeny, Dr., on the Solfatara, 595. 
 
 . . ., on volcanoes in Auvergne, 552. 
 Davidson, Mr., on liassic spirifers, 318. 
 3awson, Mr., on coal-plants, 379. 
 Dax, inland cliff at. 72. 
 )ean, forest of, coal in, 395. 
 Deane, Dr., on footprints, 347. 
 
INDEX. 
 
 675 
 
 Decken, M. von, on granite veins in Corn- 
 wall, 441 : on reptiles in Saarbruck coal-field, 
 
 396. 
 De Koninck, M., cited, 184, 183. 
 
 , on Kleyn Spawen tertiaries, 1S4. 
 
 De la Becho, Sir H., cited, 293, 297, 327. 
 
 , on Carrara marbles, 612. 
 
 , on clay-beds, 329. 
 
 . . ., on clay-ironstone, 3S6. 
 
 .on coal-measures near Swansea, 859. 
 
 . . . ., on fossil trees, South Wales, 373. 
 
 .., on granite of Dartmoor, 593. 
 . . . ., on mineral veins, 623, 625, 629. 
 
 , on term supracretaceous, 103. 
 
 ..... on trap of new red sandstone period, 
 
 555. 
 Delesse, M., analysis of minerals, 475. 
 
 , on basalt, 466. 
 
 ...., on hypersthene rock, 473. 
 . . .., on hypogeno limestone, 597. 
 . . . ., on laterite of Antrim, 471. 
 
 , on pyroxene, 465. 
 
 , on serpentine, 474. 
 
 Deluge, 4. 
 
 Denudation explained, 66. 
 .... of the Weald Yalley, 271. 
 . . . ., terraces of, in Sicily, 75. 
 
 , of volcanic craters, 504, 507. 
 
 Derbyshire, lead-veins of, 627. 
 Deshayes, M., identification of shells, 184. 
 ...., on fossil shells in Hungary, 544. 
 . . . ., on lower eocene shells, 223. 
 
 , on tertiary classification, 115. 
 
 . . . ., on upper marine strata, 1S4. 
 Desmarest, on trappean rocks, 91. 
 Desnoyers, 3tL, on Faluns of Touraine, 111. 
 Desor,"M., on glacial fauna in Noith America, 
 
 139. 
 
 Devonian system, term explained, 419. 
 .... series of North Devon, 420. 
 
 series of Eussia, 425. 
 
 .... series of United States, 426. 
 
 De Wael, M., on Antwerp strata, 173. 
 
 Diagonal, or cross stratification, 16. 
 
 DiatomacecB in tripoli, 25. 
 
 Diceras arietinum, 304. 
 
 Dicotyledonous leaves in lower chalk, 266. 
 
 Didelphys Azaroe, (recent), jaw of, 811. 
 
 Didymograpsus geminus, D. Murchisoni. 
 
 442. 
 
 Dike in St. Helena. 523. 
 Dikelocephalus Jfinnenotensis, 453. 
 Dikes at Palasonia in Sicily, 529. 
 .... defined, 6. 
 
 in Scotland, 477. 
 
 of Somma, 526. 
 
 , trappean, crystalline in centre, 476, 48S. 
 
 Diluvium, popular explanation of term, 133. 
 
 Dinornis of New Zealand, 165. 
 
 Dinotherium gignnteum, skull of, 176. 
 
 Dinothcrinm in India, 182. 
 
 Diorite, or greenstone, 467, 472. 
 
 Dip, term explained, 53. 
 
 Diplograpsus folium, D. pristis, 442. 
 
 Dirt-bed of Purbeck, 297, 300. 
 
 Dolerite, or greenstone, 466, 4T3. 
 
 Dolomite defined, 13. 
 
 Dolomitic conglomerate, 354. 
 
 Domite, or earthy trachyte, 473. 
 
 Doue, M. B. de, on volcanoes of Velay, 552. 
 
 Drift, contorted, near Cromer, 134. 
 
 ... in Ireland, 137. 
 
 ... in Norfolk, 132. 
 
 ..., meteorites in, 151. 
 
 . . ., northern, in Scotland, 130. 
 
 . .., northern, in North Wales, 136. 
 
 ... of Scandinavia, North Germany, and Eus- 
 sia, 126. 
 
 ... period, climate of, 145. 
 
 . . . period, subsidence in, 141. 
 
 . . . shells in Canada, 140. 
 Dudley limestone, 435. 
 . . . ., shales of coal near, 593. 
 Dufrenoy, M., on granite of Pyrenees, 593. 
 
 Dufrenoy, iL, on Hill of Gergovia, 558. 
 Duff. Mr. P., on reptile of old red, 412. 
 Dunker, Dr., on Wealden of Hanover, 264 
 Dura Ben, yellow sandstone of, 412. 
 Disaster ringens, inferior oolite, 315. 
 
 ECHIXODEKMS of coralline crag, 172. 
 Echinosphceriies Balthicus, 440. 
 Echinus, with Crania attached, 23. 
 Egerton, Mr., on fossils of Southern India, 255. 
 Egerton, Sir P., on fish of marl-slate, 353. 
 
 on fossil fish of Connecticut beds, 349. 
 
 , on fossils of Isle of Wight, 212. 
 
 , on saurians and fish in new red sand- 
 
 stone, 836. 
 
 , on Ichthyosaurus, 322. 
 
 Egg-like bodies in Old Bed Sandstone, 417. 
 Eggs, fossil, of snake, 125. 
 Ehrenberg, Prof., on bog-iron-ore, 26. 
 
 , on infusoria, 25. 
 
 , on Silurian foraminifera, 444. 
 
 Eifel, volcanoes of, 53S-543. 
 Elephant-bed, Brighton, 287. 
 Elephas primigenius, tooth of, 165. 
 Elgin, reptile of old red, found near, 412. 
 Elvans of Ireland and Cornwall, 629. 
 
 , term explained, 5S1. 
 
 Encrinite, plate of, overgrown with Serpida* 
 
 and Sryoaoa, 307. 
 Encrinite of Bradford, 307. 
 Encrinm liliiformis, 334. 
 Eocene foraminifera, 227. 
 
 . formations, 207. 
 
 . formations in England, 208. . 
 
 . granite, 576. 
 
 . strata in France, 194, 222. 
 
 . strata in United States, 231. 
 
 .,term defined, 115. 
 
 ., upper, near Lou vain, Belgium, 176. 
 
 . volcanic rocks, 553. 
 Eppelsheim, Dinoiherium of, 176, 191. 
 Equisetaceae of coal-period, 864. 
 Equisetites columnar^, 333. 
 Equisetuin of Virginian oolite, 331. 
 
 giganteum of S. America, recent, 364. 
 
 Equus cdballits, tooth of, 166. 
 Erman on meteoric iron in Eussia, 151. 
 Erratics, Alpine, 146. 
 
 , northern origin o 128. 
 
 Eschara disticha, chalk, 248. 
 Eschar ina oceani, chalk, 248. 
 Escher, M., on boulders of Jura, 149. 
 Estheria f, Eichmond, U. S., 331. 
 Etna, deposits of, 523. 
 Eunomia radiata, 306. 
 EuompTMltts pentagulatus, 407. 
 Euphotide, 473. 
 Eurite, 564, 590. 
 
 Euritic porphyry described, 462. 
 Eactracrinus JBriareus, lias, 821. 
 
 F ALTOS of Touraine, 111, 175. 
 Faluns, comparison of, and crag, 1T7. 
 Falunian type, distinctness o from Eocene, 
 
 179. 
 
 Falconer, Dr., on Sewalik Hills, 182. 
 Falkland Islands, 83. 
 Farnham, phosphate of lime near, 251. 
 Fascicularia aurantium, 171. 
 Fault, term explained, 62. 
 Faults, origin of, 64. 
 Favosites Gothlandica, 435 ; F. polymorpha^ 
 
 422. 
 
 Faxoe, chalk of, 238. 
 Felis tigris, tooth of, 167. 
 Felixstow, remains of cetacea found near, 173. 
 Felspar, varieties of, 453. 
 Fenestella retiformis, 352. 
 Ferns in coal-measures, 361. 
 Fife, altered rock ip, 481. 
 Fifeshire, trap-dike in, 557. 
 Fish, oldest, in Upper Ludlow, 481. 
 Fishes, fossil, of Upper Cretaceous, 249. 
 of Brown-coal, 540. 
 
676 
 
 INDEX. 
 
 Pishes of Old Eed Sandstone, 415. 
 
 .... of Wealden, 262. 
 
 Fissures filled with metallic matter, C21. See 
 Mineral veins. 
 
 Fitton, Dr., on lower cretaceous beds, 256. 
 
 ...., cited, 260, 293, 297, 303. 
 
 Fleming, Dr., on scales offish in old red, 414. 
 
 , on trap-rocks in coal-field of Forth, 556. 
 
 , on trap-dike in Fifeshire, 557. 
 
 Flints of chalk, 11, 243. 
 
 Flora, carboniferous, 360. 
 
 ...., cretaceous, 265. 
 
 .... of London clay, 216. 
 
 , permian, 356. 
 
 Flotz, term explained, 90. 
 
 Flysch, explanation of term, 231. 
 
 Foliation, term defined, 606.' 
 
 Fontainebleau, Gres de, 184, 194 
 
 Footprint of bird, 347. 
 
 Footprints of reptiles, 337, 847, 398, 899, 413. 
 
 Foraminifera, chalk, 26; tertiary, 179, 215, 
 227, 230, 231 ; paleozoic, 409, 444. 
 
 Forbes, Mr. David, on foliation, 607. 
 
 Forbes, Prof. E., on Bembridge series, 185, 
 187. 
 
 . . ., on Caradoc sandstone, 438. 
 
 ,..., onCystidese, 489. 
 
 ,..., on Hempstead, Isle of Wight series, 185, 
 192. 
 
 ...., on Mull leaf -bed, 180. 
 
 , . . ., on shells in crag deposits, 172. 
 
 ...., on cretaceous fossil shells, 254. 
 
 . . . ., on fossils of the faluns, 176. 
 
 , on fossils in drift in South Ireland, 137. 
 
 . . . ., on deep-sea origin of Silurian strata, 455. 
 
 . . . ., on echinoderms of coralline crag, 172. 
 
 , on fauna of boulder-period, 131. 
 
 ...., on migrations of mollusca in glacial-pe- 
 riod, 172. 
 
 ,...,on fossils of Purbeck group, 293, 297, 
 
 . . . ., on strata at Atherfleld, 257. 
 
 , on volcanic rocks of oolite period, 555. 
 
 ...., on depth of animal life in ^Egean, 35, 
 
 143. 
 
 . . . ., on geographical provinces, 256. 
 Forbes, Prof. James, on zones in glacier-ice, 
 
 606. 
 
 ...., on the Alps, 149. 
 Forchhammer, on scratched limestone, 127. 
 Forest, fossil, in Norfolk. 133, 136. 
 Forest marble of oolite, 305. 
 Forfarshire, old red sandstone in, 598. 
 Formation, term defined, 3. 
 Fossil ferns in carbonaceous shale, 314 
 .... footsteps, 335, 837, 338. 
 
 forest in Isle of Portland, 297. 
 
 forest in Nova Scotia, 376. 
 
 forest near Wolverhampton, 374 
 
 plants in wealden, 264 
 
 remains in caves, 159. 
 
 shells from Etna, 523; near Grignon, 226. 
 
 .... shells of Mayence strata, 190 ; of Virginia, 
 
 181. 
 
 .... shells, passim. 
 . . . ., term defined, 4 
 .... trees erect, 872. 
 .... wood, perforated by Teredina, 24 
 
 wood, petrifaction of, 39. 
 
 Fossils, arrangement of, in strata, 5. 
 . . . . , freshwater and marine, 27. 
 
 in chalk at Faxoe, 238. 
 
 in falnns of Touraine, 176. 
 
 .... of chalk and greensand, 245, 247. 
 
 of Connecticut beds, 349. 
 
 .... of coralline crag, 171. 
 
 .... of devonian system, 421. 
 
 .... of eocene strata in United States, 232, 
 
 238. 
 
 ....of Isle of Wight, 208. 
 .... of lias, 817, 328. 
 .... of London clay, 218. 
 .... of lower greensand, 258. 
 
 . . of Ludlow formation, 484 
 
 Fossils of Maestricht beds, 237. 
 .... of mountain limestone, 403. 
 .... of new red sandstone, 333, 886. 
 
 of old red sandstone. 415. 
 
 ....of oolite, 265, 301, 308. 
 
 of Permian limestone, 353, 355. 
 
 .... of Purbeck, 293. 
 
 .... of red crag, 170. 
 
 .... of Richmond, IT. S., strata, 881. 
 
 .... of Solenhofen, 302. 
 
 .... of upper greensand, 251. 
 
 .... of wealden, 261. 
 
 , petrifaction of, 39-43. 
 
 . . . ., test of the age of formations, 97. 
 Fossiliferous strata, tabular view of, 456. 
 Fournet, M., on mineral veins of Auvergne, 
 
 624 
 
 ...., on disintegration of rocks, 594. 
 ...., on quartz, 563. 
 
 Fox, Mr. E. W., 627, on Cornish loes, 628. 
 Fox, Eev. Mr., on extinct quadrupeds of Isle 
 
 of Wisht, 209. 
 
 Freshwater beds of Isle of Wight, 208. 
 .... deposits in valley of Thames, 152. 
 
 , land-shells numerous in, 27. 
 
 Freshwater formations of Auvergne, 197. 
 Freshwater formations, how distinguished from 
 
 marine. 27, 28, 30, 82. 
 
 associated with Norfolk drift, 132. 
 
 Freshwater shells in brown-coal near Bonn, 
 
 539. 
 
 Fucus vesiculosus, 33, 242. 
 Fiilgur canaliciilatus, 1S1. 
 Fuller's earth of oolite, 314. 
 Fuudy, Bay of, impressions in red mud of, 
 
 346. 
 
 Fungia patellaris (recent), 403. 
 F-usulina cylindrica, 409. 
 Fusus contrarius, 170; F. quadricostatu*, 
 
 181. 
 
 GALAPAGOS ISLANDS, animals of, 325. 
 Galeocerdo latidens, tooth of, 215. 
 Galerites albogalerus, 245. 
 Gallionella distans, G.ferruginea, in tripoli, 
 
 25. 
 
 Ganges, buried soils in delta of, 384. 
 Garnets in altered rock, 480. 
 Gases, subterranean rocks altered by, 595. 
 Gault of upper cretaceous, 250. 
 Gavarnie, flexures of strata near, 59. 
 Geoloey defined, 1. 
 Gergovia, Hill of, 558. 
 Gervillia anceps, lower greensand, 259. 
 Giant's Causeway, columns at, 483. - 
 .... basalt, age of, ISO. 
 Gibbes, E. W., cited, 233. 
 Girgenti, limestone of, 156. 
 Glacial phenomena, northern, origin of, 138. 
 Glaciers, Alpine, 146. 
 
 on Caernarvonshire mountains, 137. 
 
 Glasgow, marine strata near, 154. 
 Glenroy, parallel roads of, 86. 
 Glen Tilt, granite of, 566. 
 Glyphoza ? diibia, coal-measures, 885. 
 Gneiss, altered by granite, 570. 
 
 in Bernese Alps, 599. 
 
 .... at Cape Wrath, 568. 
 .... near Christiania, 570. 
 .... described, 588. 
 Gold, age of, in Ireland, 629. 
 
 , age of, in Ural Mountains, 630. 
 
 Goldfuss, Prof., on reptiles in coal-field, 397. 
 Goniatites crenistria, G. evolutus, 408; <? 
 
 Listeri, 886. 
 
 Gorgonia infundibuUformis, 852. 
 Goppert, Prof., on beds of coal, 360. 
 .... on petrifaction, 40. 
 Gradual increase of strata, 22. 
 Graham's Island, 488, 529. 
 Grampians, old red conglomerates in, 47. 
 Granite described, 7, 560. 
 . . . ., passage of, into trap, 565. 
 , porphyritic, 563. 
 
INDEX. 
 
 677 
 
 Granite and limestone, junction of in Glen Tilt, 
 
 566. 
 
 . . ., syenitic, talcose, and schorly, 564. 
 . .. of Cornwall and Dartmoor, 593. 
 . .. of Swiss Alps, 613. 
 
 .. rocks in connection with mineral-reins, 
 
 630. 
 
 ... of Saxony, 583. 
 . .., oldest, 5S2. 
 . .., varieties of, 568. 
 . . veins in Cornwall, 569. 
 . . veins in Cape Wrath, 568. 
 . . veins in Table Mountain, 567. 
 . . vein in White Mountains, 574. 
 . . of Arran, age of, 583. 
 . . near Christiania, 531. 
 . . dikes in Mount Battock, 567. 
 Graphic granite, 562. 
 Grahite owder of, consolidated by pressure, 
 
 Graptolites, 442. 
 
 Grdptol&ius Ludensix, Silurian, 437. 
 
 Grasshopper, wing of, in coal-measures, 386. 
 
 Gratelonp, M., on fossils in chalk, 254. 
 
 Granwacke, term explained, 429. 
 
 Great (or Bath) Oolite, 305. 
 
 Greenland, sinking of coast of, 46. 
 
 Greensand, fossils of, 251. 
 
 ...., lower, 256. 
 
 , upper, 250. 
 
 Greensburg, Pennsylvania, footprints of rep- 
 tile in coal-strata at, 397. 
 
 Greenstone, 467. 
 
 , dike of, in Arran, 477. 
 
 Gres de Beauchamp, Paris Basin, 226. 
 
 Greystone. volcanic rock, 473. 
 
 Griffiths, Mr., on geology of Ireland, 359. 
 
 Grignon, fossil shells near, 226. 
 
 Grit defined, 11. 
 
 Gryttacris lithantJiraca, wing of, 386. 
 
 Gryphcea coated with Serpulan. 22. 
 
 arcuata, G. incur-to, 29, 318. 
 
 columba, G. glolosa, 247; G. virgula, 
 301. 
 
 Gryphite limestone, or lias, 318. 
 
 Guadaloupe, human skeleton of, 120. 
 
 Gunn, Mrs . on Norwich flints, 244. 
 
 Gutbier, Col. von, on Permian flora. 356. 
 
 Gyrolepis tenuistriatus, scale of, 336. 
 
 Gypseous eocene marls, 223, 224. 
 
 Gypsum defined, 13. 
 
 HALL, Sir Jas., experiments on fused minerals, 
 
 528. 
 ..... on curved strata, 48. 
 
 ..., Capt B., cited, 476. 523, 567. 
 ffalysites catenulatua, Silurian, 435. 
 Hamilton, Sir W., on eruption of Vesuvius, 
 
 526. 
 
 Hamites spiniger, ganlt, 251. 
 Harris, Major, on salt lake in Ethiopia, 344. 
 Hartung. Mr. G., on Teneriffe, 510. 
 ...., on Madeira, 514, 518. 
 Hartz. bunter-sandstein of. 335. 
 Hastings, Lady, fossils collected by, 211. 
 Hastings sand, 262, 2-53. 
 Hautes Alpes. rocks of, 579. 
 Haiiy cited, 463. 
 
 Hawkshaw, Mr., on fossil trees in coal, 372. 
 Hayes, Mr. T. L., on icebergs, 127. 
 Headon Hill sands described, 212. 
 .... series of Isle of Wight described, 210. 
 Hebert, M, on upper eocene beds, 184 
 
 , on age of Kleyn Spawen beds, 184 
 
 on pisolitic limestone, 236. 
 
 Hebrides, dikes of trap in, 477. 
 
 Heidelberg, varieties of granite near, 563. 
 
 Heliolites porosa, 422. 
 
 Helix labyrinthica, 211 ; H. occlusa, 209 ; H. 
 
 plebeia.Wl; H. Turonensis, %Q. 
 Uemicidaris Purbec.kenxis, 294. 
 Hemipnewtex radlatux, 233. 
 Ifemitelites Brovmii, 314 
 Uempstead beds, Isle of Wight, 185, 192. 
 
 Henfrey, Mr. A., on food of Mastodon, 144 . 
 Henslow, Prof., on fossil cetacea in Suffolk, 
 
 173. 
 . . . ., on fossil forests, 297. 
 
 , on altered rock near Plas Newydd, 480. 
 
 HerscheL Sir J., on slaty cleavage, 602. 
 Hertfordshire pudding-stone, 35. 
 Hesse Cassel, sands of, 186. 
 Heterocercal fish, tail of, 353. 
 Hibbert, Dr., on volcanic rocks, 542, 552. 
 
 , on coal-field at Burdiehouse, 386. 
 
 High Teesdale, garnets in altered rock at, 
 
 Hildburghausen, footprints of reptile at, 835, 
 337. 
 
 Himalaya, tertiary Inammalia of, 182. 
 
 , elevated fossiliferous rocks in, 4. 
 
 Hippopodium ponderosum, lias, 319. 
 
 Hippopotamus, tooth of, 166. 
 
 Hippurites organisans, chalk, 253. 
 
 Hippnrite limestone, 253. 
 
 Hitchcock, Prof., on footprints, 346. 
 
 Hoffmann, Mr, on Lipari Islands, cited, 595. 
 
 . . . ., on cave near Palermo, 74 
 
 , on Carrara marble, 612. 
 
 Hooghley River, analysis of water of, 41. 
 
 Holopty'chius nobilissimm, scale of, 414 
 
 .... Ribberti, tooth of, 396. 
 
 Homalonotus armatus, 425. 
 
 delphinocephalus, 437. 
 
 Homocercal fish, tail of, 353. 
 
 Hopkins, Mr., on fractures in Weald, 280. 
 
 Horizontal strata, upheaval of, 45. 
 
 Horizontally of strata, 15. 
 
 .... of roads of Lochaber, 88. 
 
 Hornblende, 463. 
 
 rock, or amphibolite, 473, 590. 
 
 Hornblende-schist, 588, 596. 
 
 Homer, Mr., on ecology of Eifel, 538. 
 
 on Holoptychius, 396. 
 
 Homes, Dr., on shells of Vienna tertiary basin, 
 179. 
 
 Hubbard, Prof, on granite-vein in White Moun- 
 tains, 377. 
 
 Hugi, M., on Swiss Alps, 614 
 
 Humboldt, on uniform character of rocks, 616. 
 
 Hungary, trachyte of, 467. 
 
 , volcanic rocks of, 544. 
 
 Hunt, Mr., experiments on clay-ironstone, 886. 
 
 Hntton. opinions of, 60. 
 
 Hnttonian theory, 92. 
 
 ffycsna spelcea, tooth of, 167. 
 
 Hybodus reticulatus, tooth and ray of. 321. 
 
 .... plicatilis, teeth of, 336. 
 
 Hyrnenocaris vermicauda, 448. 
 
 Hypersthene rock, 473. 
 
 Hypogene, term defined. 9. 
 
 .... rocks, mineral character of, 615. 
 
 or metamorphic limestone, 589. 
 
 IBBETSOX, Capt.. on chalk, Isle of Wight, 250. 
 Ice, rocks drifted by, 120. 
 Icebergs, stranding of, 135, 143. 
 
 , magnitude of, 128. 
 
 Iceland, icebergs drifted to, 143. 
 Ichthyolites of old red sandstone, 419. 
 Ichthyosaurus communis. skeleton of. 823; 
 
 paddle of, 324 
 Igneous rocks, 6. 
 
 of Sicbengebirge and Westerwald, 540. 
 
 .... ofValdiNoto, 438. 
 Iguanodon, notice of the, 260, 262. 
 Iguanodon Mantelli, teeth of, 261. 
 India, cretaceous system in, 255. 
 
 freshwater deposits of, 182. 
 
 oolitic formation in, 332. 
 
 Indusial limestone, Auvergne, 200. 
 Inferior oolite, 314. 
 Infusoria in tripoli, 24 
 Inland sea-cliffs in south of England, 71. 
 Inoceramus Lamarckii, chalk, 247. 
 In&ct, wing of nenropterous, 328. 
 Insects in coal, 3S5. 
 .... in lias, 327. 
 
678 
 
 INDEX. 
 
 Insects In oolite, 809. 
 .... in Purbeck beds, 800. 
 Invertebrate animals, period of, 453. 
 Ireland, coal strata of, 359. 
 
 , Devonian plants of, 414. 
 
 ...., drift in, 137. 
 
 Isastrcea oblonga, I. Tisburientts, 301. 
 
 Ischia, volcanic cones in, 525. 
 
 . . . ., post-pliocene strata of, 118. 
 
 Isle of Wight, freshwater beds of, 210. 
 
 Isomorphism, theory of, 464. 
 
 JACKSON, Dr. C. T., analysis of fossil bones, 
 
 144. 
 James, Capt., on fossils in drift, South Ireland, 
 
 137. 
 Java, stream of sulphureous water, 223. 
 
 , volcanoes of, 492. 
 
 Jobert, M., on Hill of Gergovia, 553. 
 
 Joints, 601. 
 
 Jorullo, lava-stream of, 574. 
 
 Junghuhn, Dr., on Javanese volcanoes, 492. 
 
 Jura, alpine blocks on, 148. 
 
 limestone, 303. 
 
 . . . ., structure o-f, 55. 
 
 KANGAROO, fossil and recent, jaws figured, 162. 
 Kaup, Prof, on footprints of Cheirotherium. 
 
 337. 
 
 Kaye, Mr., on fossils of Southern India, 255. 
 Keeling Island, fragment of greenstone in, 242. 
 Keilhau, Prof, cited, 581, 593. 
 ..... on dike of greenstone, 478. 
 ..... on foliation, 607. 
 
 , on gneiss near Christiania, 570. 
 
 , on granite, 571. 
 
 Kelloway rock, 34. 
 
 Kentish chalk, sandgalls in, 82. 
 
 .... rag, lower greensand, 257. 
 
 Keuper, the, 333. 
 
 Kilauea, volcanic crater of, 490. 
 
 Killas in granite of Cornwall, 593. 
 
 Kilkenny yellow sandstone, fossil plants of, 
 
 Kimmeridge clay, 300. 
 
 King, Dr., on footprints of reptile, 398. 
 
 King, Prof., on Permian group and fossils. 
 
 350. 
 
 Kirkdalo, cave at, 160. 
 Kyson, in Suffolk, strata of, 218. 
 
 LABTRINTHODON J^QEKI, tooth of, 338, 339. 
 
 pachygnathus, outline of, 340. 
 
 Lacustrine strata of Auvergne, 202. 
 Lagoons at mouth of rivers, 33. 
 
 of Bermuda Islands, 240. 
 
 Lake craters of Eifel, 540. 
 
 crater of Laaeh, 543. 
 
 Lakes, deposits in, 8. 
 
 Lamarck on bivalve mollusca, 29. 
 
 Lamna elegans, tooth of, eocene, 215. 
 
 Land, rising and sinking, 45. 
 
 Landenian, or lower eocene beds, 235. 
 
 Lapldification of fossils, 43. 
 
 La Eoche, estuary of, 14. 
 
 Laterite, 471, 473. 
 
 Lava, 469. 
 
 .... current, Auvergne, 546. 
 
 .... current, Madeira, view of, 518. 
 
 , relation to trap, 486. 
 
 .... stream of Jorullo, 574. 
 
 .... streams, effects of, 6. 
 
 .... of Stromboli, 574. 
 
 Lea, Mr., footprints of reptile discovered by, 
 
 400. 
 
 Leaf-bed, miocene, of Isle of Mull, 179. 
 .... in Madeira, 515. 
 Lead-veins in Permian rocks, 630. 
 Leda amygdaloides, 218 ; L. DesJiayesiana, 
 
 188; L.oblonga,m. 
 Lehman on classification of rocks, 90. 
 Leibnitz, theory of, 94. 
 
 Leidy, Dr., on supposed cotaceans of the clialk, 
 
 Lepidodendra, 862. 
 
 Lepidodendron, stem of, from Ireland, 414. 
 
 .... Sternbergii, 363. 
 
 Lepidostrobus ornatus. 363. 
 
 Lepidotus gigas, scales of, 320. 
 
 .... Mantelli, teeth and scale of, 262. 
 
 Leptcena depressa, 445 ; L. Moorei, 319. 
 
 Leptignite, or whitestone, 564. 
 
 Lewes, coomb near, 276. 
 
 Lias, 317. 
 
 . and oolite, origin of, 328. 
 
 ., fossil plants of, 328. 
 . in United States, 330. 
 . period, volcanic rocks of, 555. 
 . ., plutonic rocks of, 579. 
 Liebig, Prof., on conversion of coal into lignite, 
 
 . . . ., on preservation of fossil bones in caverns, 
 
 161. 
 
 Lima gigantea, 318 ; L. Hoperi, 247. 
 Lima, South America, recent strata of, 120. 
 Limagne d' Auvergne, freshwater formations of, 
 
 197. 
 Limburg, or upper eocene strata of Belgium, 
 
 l'8b 
 
 Lime in solution, source of, 42 ; scarcity of, in 
 
 metamorphic rocks, 617. 
 Limestone brecciated, 851. 
 ., crystalline, 851. 
 ., compact, 352. 
 ., fossiliferous, 352. 
 ., hippurite, 252. 
 ., indusial, Auvergne, 200. 
 of Jura, 303. 
 , magnesian, 350. 
 , mountain, fossils of, 403. 
 , primary or metamorphic, 589. 
 of Devonian system in Germany, 421. 
 Limulus rotundatus, coal-measures, 385. 
 Lindley, Dr., cited, 265. 
 Lingula flags of lower Silurian, 448. 
 Lingula Davisii, 448 ; L. Dumortieri, 173 ; L. 
 
 Lewisii, 433. 
 
 Lipari Islands, rocks altered by gases in, 595. 
 Lithodomi in beaches of North America, 78. 
 
 in inland cliifs, 73. 
 
 Lithostrotion basalt if or me, L. flori/otvne, Z. 
 
 striatum, 404. 
 
 Lituites giganteus, Silurian, 434, 
 Llandeilo flags, 439. 
 Loam defined, 13. 
 Lochabar. parallel roads of, 86. 
 Lodes. See Mineral veins, 620. 
 Loess of valley of Ehine, 121. 
 
 , fossil land-shells of, figured, 124. 
 
 Logan, Mr., on coal-measures of South Wales, 
 
 360. 
 . . . ., on footprints in Potsdam sandstone, 452. 
 
 , on fossil forest in Nova Scotia, 383. 
 
 , on lower Silurian rocks of Canada, 446. 
 
 London clay, 216. 
 
 Lonsdale, Mr., cited, 158 ; on corals, 182. 
 
 , on corals of Normandy, 177. 
 
 , on fossils in white chalk, 26. 
 
 , on old red sandstone of South Devon. 
 
 419. 
 
 , on Stonefield slate, 309. 
 
 Lonsdaleiafloriformis, carboniferous, 404 
 
 Louvain, eocene strata near, 188. 
 
 Loven on shells of Norway, 119. 
 
 Lucina serrata, eocene, 216. 
 
 Ludlow formation, 430. 
 
 Lund, cited, 164. 
 
 Lycett, Mr., on shells of oolite, 309. 
 
 Lycopodium densum (recent), 363. 
 
 Lyme Reals, lias at, 327. 
 
 Lym-Fiord invaded by the sea, 33. 
 
 ....,kelpin, 242. 
 
 Lymnwa caudata. 211 ; L. longiscata, 29, 
 
 209. 
 Lyons, coal-mino near, 374. 
 
 MACACUS, tooth of, Eocene, 219. 
 
INDEX. 
 
 679 
 
 M'Andrew, Mr., on scarcity of fish-bones on 
 
 sea-bottom, 455. 
 MacCulloch, Dr., on age of Arran granite, 584. 
 
 . ., on altered rock in Fife, 481. 
 
 . ., on basaltic columns in Skye, 433. 
 ., on denudation. 6T. 
 , on granite of Aberdeensbire, 565. 
 , on hornblende-schist, 596. 
 , on igneous rocks of Scotland, 4S3. 
 , on Isle of Skye, 36. 
 , on overlying rocks, 8. 
 , on parallel roads, ST. 
 , on trap-vein in Argyleshire, 477. 
 Maclaren, Mr., on erratic blocks in Pentlands, 
 
 131. 
 
 Maclure, Dr., on volcanoes in Catalonia, 531. 
 Madurea Logani, Silurian, 446. 
 Macropus atlas, 162; jaw of, 162; tooth of, 
 
 163. 
 
 major (recent), jaw of, 162. 
 
 Madeira, structure of, 511-518. 
 
 . ..., trachyte overlying basalt in, 522. 
 
 , view of dike in inland valley in, 476. 
 
 Maestricht beds, 237. 
 
 Magnesian limestone, concretionary structure 
 
 of, 37. 
 
 defined, 13. 
 
 groups, 350. 
 
 Maidstone, fossils in white chalk of, 250. 
 Mammalia, extinct, above drift in United States, 
 
 143. 
 
 , extinct, of basin of Mississippi, 121. 
 
 ....,/08*il teeth o/ 166. 
 Mam mat, Mr., cited, 69. 
 Mammifer in Pnrbeck beds, 295, 457. 
 .... in Stouesfield oolite, 311. 
 
 in trias near Stuttgart, 341. 
 
 Mammoth, tooth of, 165. 
 
 Mansfield in Thuringia, Permian formation at, 
 
 356. 
 
 Mantell, Dr., cited, 242, 262, 264, 286. 
 . . . ., on belemnite, 805. 
 
 , on chalk-flints, 286. 
 
 , on Brighton elephant-bed, 287. 
 
 . . . ., on freshwater beds of Isle of Wight, 209. 
 
 , on ignanodon, 260. 
 
 , on wealden group, 259, 286. 
 
 , on reptile in old red, 413, 589. 
 
 ManteUia megalophylla, Purbeck, 296. 
 Map to illustrate denudation of Weald, 271. 
 
 of eocene beds of Central France, 195. 
 
 Marble defined, 12. 
 Marl defined, 18. 
 
 in Lake Superior, 36. 
 
 , red and green in England, 335. 
 
 Marl-slate defined, 13. 
 Marsupites Milleri, chalk, 245. 
 Martin, Mr., cited, 280. 
 
 , on cross fractures in chalk, 274 
 
 Martins, Mr. C., on glaciers of Spitzbergen, 142. 
 Massachusetts, plumbago in, 596. 
 Mattodon angustidens, tooth of, 165. 
 Mastodon giganteus, in United States, 143. 
 Mastodonsaurus, tooth of, 338. 
 Mayence basin tertiaries, 190. 
 May Hill, Silurian strata of, 431. 
 Mediterranean and Eed Sea, distinct species in, 
 
 100. 
 
 , deposits forming in, 99. 
 
 Meaalodon cucullatus, 423. 
 Megatherium, tooth of, S. America, 167. 
 Melania inouinata, 29, 220 ; M. turriti9ima, 
 
 208. 
 
 Mtlanopsis buccinoidea (recent), 29. 
 Melaphyre, or black porphyry, 473. 
 Menai Straits, marine shells in drift, 136. 
 Mendips, denudation in, 63. 
 Mersey, in Kent, ancient channel of, 120. 
 Metalliferous veins. See Mineral veins. 
 Metals, supposed relative ages of, 62S. 
 Metamorphic rocks, 537. 
 . . . ., defined, 8. 
 , less calcareous than fossiliferons rocks, 616. 
 
 ..., order of succession of, 615. 
 
 Metamorphic rockg, glossary of, 590. 
 
 strata, origin of, 591. 
 
 structure, origin of, 536. 
 
 Meteorites in drift, 151. 
 
 Mexico, lamination of volcanic rocks in, 605. 
 
 Meyer, M, H. von, cited, 153. 
 
 , on reptile in coal, 497. 
 
 , on sandstone of the Vosees, 335. 
 
 , on Wealden of Hanover and Westphalia, 
 
 Mica-schist, 584. 
 
 Micaceous sandstone, origin of, 14. 
 Micraster cor-anguinum, chalk, 245. 
 Microconchus carbonarius, carboniferous, 384. 
 Microlestes antiquus, teeth of, triassic mam- 
 
 mifer, 340. 
 
 Miller, Mr. H., on origin of rock-salt, 344. 
 . . . ., on old red sandstone, 412, 418. 
 
 , on fossil trees of coal near Edinburgh, 376. 
 
 Minchinhampton, fossil shells at, 308. 
 Mineral character of aqueous rocks, 10, 97. 
 composition, test of age of volcanic rocks, 
 
 521. 
 
 springs, connected with mineral-veins, 627 
 
 veins and faults, 618, 620. 
 
 veins of different ages, 620. 
 
 veins, pebbles in, 622. 
 
 veins, various forms of, 619. 
 
 veins near granite, 624. 
 
 Mineralization of organic remains, 38. 
 Minerals, table of analyses of simple, 475. 
 Miocene faluns of the Loire, 176. 
 
 formation, 175. 
 
 .... formation in Isle of Mull, 179. 
 
 in United States, 180. 
 
 . . . ., (lower), strata of Isle of Wight, 185. 
 .... mammalia of Sewalik Hills, 182. 
 
 of the Bolderberg, 178. 
 
 period, volcanic rocks of, 538. 
 
 , term defined, 116; 
 
 Mississippi, fluviatile strata and delta of, 3, 121, 
 
 122. 
 
 Mitchell, Sir T., on Australian caves, 162. 
 Mitscherlich, Prof., on augite and hornblende, 
 
 . . . ., on mineral composition of Somma, 526. 
 
 Mitra scabra, Barton clay, 213. 
 
 Modiola acuminata, Permian, 351. 
 
 Modon, lithodomi in cliff at, 73. 
 
 Molasse of Switzerland, 179. 
 
 Monkey, tooth of, eocene, 219. 
 
 Mons, flexures of coal at, 53. 
 
 Mont Blanc, talcose granite of, 577. 
 
 Mont Dor, Auvergne, 545. 
 
 Montlosier, M., on Auvergne volcanoes, 550. 
 
 Moraine, term explained, ~123. 
 
 Moraines of glaciers, 147. 
 
 Morea, inland sea-cliffs of, 73. 
 
 ....', trap of, 555. 
 
 Morris, Mr., on fossils at Brentford, 153. 
 
 Morton, Dr., on cretaceous rocks, 254. 
 
 Morven, basaltic columns in, 483. 
 
 Mosasaunis Camperi, jaws of, from Maes 
 
 tricht, 238. 
 
 Mountain limestone, fossils of, 403. 
 Mull, Isle of, Miocene leaf-bed of, 119. 
 Miinster, Count, on fossils of Solenhofen, 302. 
 Murchison, Sir E., cited, 278, 285, 287. 
 . . , on eocene gneiss, 599. 
 
 , on volcanic rocks of Italy, 530. 
 
 , on new red sandstone, 336. 
 
 , on age of Alps, 231. 
 
 , on age of gold in Eussia, 629. 
 
 , on erratic blocks of Alps, 150. 
 
 , on granite, 580, 583. 
 
 , on primary strata in Eussia, 129. 
 
 , on joints and cleavage, 601. 
 
 , on old red sandstone of S. Devon, 419, 422. 
 
 , on pentamerus, 433. 
 
 , on Sflnrian strata of Shropshire, 558. 
 
 , on Swiss Alps, 614 
 
 , on term Permian, 350. 
 
 , on term Silurian, 429. 
 
 , on tilestons, 430. 
 
680 
 
 INDEX. 
 
 Murchisonia graciUs, Silurian, 446. 
 Murex atoeolatus, red crag, 170. 
 Muschelkalk, 338. 
 Myliobatea Edwardsi. teeth of, Bracklesham, 
 
 215. 
 Mytilus septifer, Permian, 351. 
 
 NAGELFLUH, or conglomerate of Alps, 179. 
 Naples, post-pliocene formations near, 524. 
 
 , recent strata near, 117. 
 
 , rising of land at, 118. 
 
 Nassa granulata, red crag, 170. 
 Natica (recent), spawn of, 417. 
 
 clausa, 130 ; N. helicoides, 155. 
 
 Nautilus cent rails, N. ziczac, 218; N. Dani- 
 
 cus, 239; N..phcaiu8, 258; N. truncatus, 
 
 319. 
 
 Navarino, lithodomi found in cliff at, 73. 
 Nebraska, U. S., upper eocene of, 206. 
 Necker, M. L. A., cited, 569. 
 . . ., on composition of cone of Somma, 526. 
 . . ..on granite in Arran, 584. 
 . . ., on granitic rocks, 571. 
 .. ., on Swiss Alps, 614. 
 . . ., terms granite " underlying," 8. 
 Nelson, Capt., drawing of Bermuda, 79. 
 
 , on chalk of Bermuda Island, 240. 
 
 Neocomian, or lower cretaceous, 256. 
 
 Neozoic type of corals, 403. 
 
 Neptunian theory, 91. 
 
 NerincBd Goodhallii, N. hieroglypMca, 303. 
 
 Nerita conoidea, Ml Schemidelliana, 228 ; 2T. 
 
 costulata, 308 ; N. granulosa, 30. 
 Neritina concava, 211 ; JW. globvilus, 30. 
 Newcastle coal-field, great faults in, 64. 
 Newcastle, fossil tree near, 311, 317. 
 New Jersey, cretaceous strata of, 255. 
 
 , Mastodon gigaateus in, 143. 
 
 New red sandstone, distinction from old, 832. 
 
 , its subdivisions, 333. 
 
 of United States, 346. 
 
 , trap of, 555. 
 
 New York, Devonian strata of, 426. 
 
 , Silurian strata of, 444. 
 
 New Zealand, absence of quadrupeds, 164. 
 Niagara limestone, Silurian fossils of, 445. 
 
 recent shells in valley of, 144. 
 
 Nipadites eliipticus, 216. 
 Nodosaria, chalk, 26. 
 Noeggerath, M., cited, 538. 
 Noeggeratlda cuneifolia, 357. 
 Nomenclature, changes of, 93. 
 Norfolk, buried forest, 133, 136, 153. 
 . . . ., drift, 132. 
 
 Normandy, chalk-cliffs and needles, 269. 
 Northwich, beds of salt at, 343. 
 Norwich crag, fluvio-marine, 154. 
 
 , sandpipes near, 82. 
 
 Nova Scotia, coal-seams of Cape Breton, 312. 
 
 , fossil forest of coal in, 320. 
 
 Nucula, Cobboldice, 155 ; Jf. Deshayesiana, 
 
 183. 
 Nummulites, whether found in upper eocene, 
 
 189. 
 Nummulites earponens, 231 ; .A 7 ". Icevigata, 215 ; 
 
 2T. Puschi, 230. 
 Nummulitic formation, 229. 
 Nyst, M., cited, 1S8. 
 
 OBOLUS APOLIJNIS, Eussia, 444. 
 
 Oenyhausen, M. von, on Cornish granite veins, 
 
 569. 
 
 Ohio, Falls of, Devonian coral-reef of, 427. 
 Old red sandstone, 411. 
 
 , in Forfarshire, 598. 
 
 , trap of, 558. 
 
 OldKamia antiqua, 0. radiata. 449. 
 Olenus mierurus, Cambrian, 448. 
 OUva Dnfreanli t miocene, 178. 
 Olot, extinct volcanoes near, 531. 
 Omphyma turinnatum, Wenlock, 435. 
 Onchus fonnistfiatus, Silurian, 432. 
 Oolite, 291. 
 and lias, origin of, 319. 
 
 Oolite, inferior, fossils of, 314. 
 
 in France, 293. 
 
 , plutonic rocks of, 579. 
 
 , term defined, 12. 
 
 , volcanic rocks of, 555. 
 
 Oolitic group in France, 293, 302. 
 ...., United States, 330. 
 Opkioderma Egertoni, lias, 320. 
 Ophite and ophiolite, 473. 
 Opossum, part of jaw of, 219. 
 Orbigny, M. d', cited, 253. 
 
 , on fossils of nummulitic limestone, 233. 
 
 , on subdivisions of cretaceous series, 237. 
 
 , on Vienna basin forarninifera, 179. 
 
 Organic remains, criterion of age of formation, 
 
 , test of age of volcasic rocks, 521. 
 
 Ormerod, Mr., on trias of Cheshire, 343. 
 Orthis elegantula, 481 ; 0. grandis, 0. trice- 
 
 naria, 0. vespertilio, 440. 
 Orthoceras laterale, 408 ; 0. Ludense, 0. ven- 
 
 tricosum, 434. 
 
 Orthoclase, or common felspar, 463. 
 Osborne, or St. Helen's series, Isle of Wight, 
 
 192, 210. 
 
 Osnabruck, in "Westphalia, tertiary strata of, 178. 
 Ostrea acuminata, 314; 0. carinata, 0. co- 
 lumba, 0. vesicularis, 247 ; 0. ditforta, 294 ; 
 0. expansa, 0. deltoidea, 301 ; gregaria, 
 303; O. Marahii, 316. 
 Otodus obliquus, tooth of; 215. 
 Overlying, term applied to volcanic rocks, 8. 
 Owen, Dr. Dale, on oldest fossiliferous rocks of 
 Wisconsin, 453. 
 
 , Prof., cited, 161, 173, 262, 310, 312, 313, 338. 
 , on amphitherium, 310. 
 , on birds in New Zealand, 165. 
 , on bone-caves in England, 160. 
 , on footprints, 347. 
 , on fossils in Australia, 162. 
 , on fossil monkey, 218. 
 , on fossil quadrupeds, 163. 
 , on ichthyosaurus, 323. 
 , on reptife in coil, 397. 
 , on serpent of Bracklesham, 214. 
 , on snake of Sheppey, 217. 
 , on thecodont saurians, 303. 
 , on zeuglodon, 233. 
 Oxford clay, 304. 
 Oyster beds, 220. 
 
 PACIFIC, coral-reefs of, 240. 
 Palcechinus gigas, 465. 
 Palceoniscus, Permian, outline of, 353. 
 PalcKoniscus comptu*, scale of, P. elegans, 
 
 scale of, P. glap/iyruQ, scale of, 354. 
 Palaeontology, term explained, 1<!3. 
 Palceophis typhceuft, vertebrae of, 214. 
 Palceosaurus platyodon, tooth of, 355. 
 Palceotherium, magnum, outline of, 210 
 Palagonia, dikes at, 529. 
 Palagonite tuff; 470. 
 Palermo, caves near, 74. 
 Palma, Isle of, map of, 495. 
 
 , structure of, 494-508. 
 
 Paludina (Auvergne). 201 ; P. lenta, 29, 193. 
 .... marginata, P. minuta, 132. 
 
 (Mayence), 190 ; P. orbicularis, 209. 
 
 Pampas, extinct quadrupeas of, 163. 
 
 Paradoxides Eohemicus, Cambrian, 450. 
 
 Parasmilia centrabis, chalk, 403. 
 
 Parallel roads, 86. 
 
 Pareto, M., on Carrara marble, 612. 
 
 Paris basin, 93. 
 
 Parka decipiens of Forfarshire, 417. 
 
 Parkinson, Mr., on eras:, 110. 
 
 Parrot, Dr. F., on salt-lakes of Asia, 344. 
 
 Patella rugosa, great oolite, 308. 
 
 Pear-Encrinite, Brad ford -clay, 306. 
 
 Pearlstone, volcanic rock, 474. 
 
 Pebbles in chalk, 241. 
 
 Pecopteris lonchitica, roal, 361. 
 
 Pecten Beave.ri, 246; P. ixlandicus, 130; P. 
 
 jacobcBus, 158. 
 
INDEX. 
 
 681 
 
 Pecten papyraeeus, 336; P. quinquecostatu*, 
 
 247. 
 
 Pegmatite, variety of granite, 562. 
 J'untacrinus Briareus, lias, 320. 
 I>entannnu Knightii, 433 ; P. Icevit, 483. 
 Pentland hills, Mr. Maclaren on, 181. 
 Peperino, volcanic tuff, 474 
 Pepys, Mr., cited, 41. 
 Permian flora, distinct from that of coal, 353. 
 
 formation of Thuringia, 356. 
 
 group described, 350. 
 
 Perna Jfulleti, lower greensand, 253. 
 
 Petrifaction of fossil wood, 39. 
 
 . ..., process of, 43. 
 
 Philipni, Dr., on fossil shells near Naples, 118. 
 
 . . ., on Hesse Cassel beds, 186. 
 
 . . ., on marine shells in caves of Sicily, 160. 
 
 . ... on tertiary shells of Sicily, 156. 
 
 Phillips, Prof, ci'ed, 308, 318. 
 
 . .., on cleavage, 603. 
 
 . ... on terminology, 102. 
 
 . . . ., Mr. W., on kaolin of China, 11. 
 
 Phacops caudatus, Silurian, 436. 
 
 Phascolotherium Bucklandi, jaw of, 312. 
 
 Pha-sianetta ffeddingtonenfii#, coral-rag, 39. 
 
 Pfdeboptei-is contigua, oolite, 314, 
 
 Plwladomyafidieula, oolite, 315. 
 
 Phonolite, or clinkstone, 472. 
 
 Phorus extensus, London clay, 218. 
 
 Phosphate of lime, 251. 
 
 P/iragmoeeras ventricosum, Lndlow, 434. 
 
 Phryganea, indusice, of, 201. 
 
 , (recent), larva of, 201. 
 
 Phyllade or clay-slate, 590. 
 Physa BHstovii, Purbeck, 295. 
 
 columnaris, P. hypnorum (recent), 29. 
 
 Picton, Nova Scotia, catamites near, 318. 
 
 Pilla, M., on age of Carrara marble, 612. 
 
 Piiiidiumamnicum, 133. 
 
 Pisolitic limestone of France, 235. 
 
 Pitchstone, or retinite, 474. 
 
 Placodus gigas, teeth of, 335. 
 
 Plagiostoma giganteum, 318; P. Hbperi, P. 
 
 spinosum, 247. 
 Planitz, tripoli of, 26. 
 
 Planorbis di&ciis, 209 ; P. euompfialus, 29, 211. 
 P as Newydd, rock altered by dike near, 480. 
 Plastic clays, 219. 
 Playfair, cited, 45, 92. 
 
 , on faults, 62. 
 
 . . . ., on Huttonian theory of stratification, 60. 
 Plectrodm miruMlis, 432. 
 Pleaiosaurus dolicfiodiirus, 323. 
 Pleurodictyum problematic-urn, 425. 
 Pleurotoma attenuata, 216 ; P. rotata, 31. 
 Pleurotomaria carinata, P.flammigera, 406. 
 Pleurotomaria granulata, P. ornata, 315. 
 Plieninger, Professor, on triassic mammifer, 340. 
 Pliocene, newer, period, 126. 
 
 , newer, strata, 152. 
 
 strata in Sicily, 155. 
 
 , older, in United States, 180. 
 
 ... strata, 167. 
 
 period, volcanic rocks of, 529, 530. 
 
 , term defined, 116. 
 
 Plomb du CantaL, described, 552. 
 Plumbago in Massachusetts, 596. 
 Plutonic rocks, 7, 573. 
 
 of carboniferous period, 580. 
 
 .... of oolite and lias, 5T9. 
 
 , recent and pliocene, 574, 
 
 .... of Silurian period, 5S1. 
 
 , age of, how tested, 573. 
 
 Plutonic and sedimentary rocks, diagram of, 576. 
 
 Pluvial action, effects of, 279. 
 
 Podocarya, fruit of, oolite, 313. 
 
 Poggendorf, cited, 594. 
 
 Poikilitic formation, 350. 
 
 . . . ., term explained, 332, 
 
 Poly co&lia prof 'unda, Permian, 403 
 
 Pomel, M., on mammalia of Auvergne, 203, 421. 
 
 Ponza Islands in Mediterranean, 486, 605. 
 
 Porphyritic granite, 563. 
 
 Porphyry, 467, 4oS. 
 
 Portland, Isle of, fossil forest in, 29T. 
 
 Portland stone, 300. 
 
 Portlock, Col., on Tyrone Silurian rocks, 443, 
 
 Posidonia minuta, triassic, 334. 
 
 Posidonomya?, Richmond, U. 8^ 331. 
 
 ---- Beoheri, carboniferous, 410. 
 
 Post-pliocene formations, 116. 
 
 ____ , period, volcanic rocks, 523. 
 
 Potsdam sandstone at Keeeeville, 451. 
 
 ---- sandstone, tracks on, 452. 
 
 ---- sandstone in Canada, 446. 
 
 Pottsville, coal-seams near, 383. 
 
 ---- , footprints of reptile near, 400. 
 
 Pozzolana, 36. 
 
 Pratt, Mr., on ammonites, 304. 
 
 ..... on extinct quadrupeds of Isle of Wight, 
 
 209. 
 
 Precipitation of mineral matter, 41. 
 Predazzo, altered rocks at, 581. 
 Prestwich, Mr., cited, 69. 
 ____ , on "Weald denudation, 281. 
 ____ , on English eocene strata, 203, 212, 216, 219. 
 ..... on coal-measures of Colebrook Dale, 62, 
 
 3S5. 
 
 Prevost, M. C., on Paris basin, 223, 224, 225. 
 Productus oalviis, P. ftorridus, 352. 
 Productus antiquatus, P. semiretieulatus, 
 
 405. 
 
 Progressive development, theory of, 453. 
 Protogine, or talcose granite, 564. 
 Psammodus poroaut, tooth of, 409. 
 Psaronites in Germany and France, 357. 
 Pseudocrinites bi/asciatits, 436. 
 Pterichihys, old red, 419. 
 Pterodactylm crasfsirostris, 302. 
 PterophyUum comptum, 314 
 Pterygotue Anglicue, 415 ; P. problematicus, 
 
 Ptychodus decurrew, tooth of, 249. 
 
 Puggaard, Mr., on Moen drift, 2S5. 
 
 Pumice, 469. 
 
 Pupa muncorum, 124 ; P. tridens, 30. 
 
 Purbeck beds, 891, 293. 
 
 Purpwroidea nodulata, oolite, 308. 
 
 Puy de Tartaret, 548. 
 
 Puy de Pariou, 551. 
 
 Puzzuoli, elevation and depression of land at, 
 
 525. 
 
 ____ , post-pliocene strata at, 117. 
 Pygopterus mandibularis, scale of, 354. 
 Pyrenees, cretaceous rocks of, 589. 
 ____ , curvatures of strata in, 58. 
 ---- , granite of, 593. 
 ---- , nummulitic formation of, 230. 
 Pyrocene, or augite, 465. 
 Pyrula reticulata, coralline crag, 172. 
 
 Q0ADRTJMAXA, fossil, 219. 
 
 Quarrington Hill, basaltic dike near, 520. 
 
 Quartz, 561. 
 
 Quartzite, or quartz-rock, 589. 
 
 iosuz, 253. 
 .... Mortoni, chalk, 248. 
 Kadnorshire, stratified trap of, 558. 
 Rain-prints, fossil in coal-shale, 384 
 Eamsay, Prof. A. C., on denudation, 68. 
 ____ on granite in Arran, 584 
 ---- on section near Bristol, 102. 
 .... on Welsh glaciers, 137. 
 ____ on foliation of crystalline schists, 609. 
 ---- on Caradoc sandstone, 438. 
 Rastritesperegrinux, 442. 
 Kecent strata defined, 11T. 
 ____ , near Naples, 117. 
 
 Eedfield, Mr., on glacial fauna in America, 139. 
 ____ , on fossil fish, 349. 
 Red sandstone, origin of, 342. 
 Eed Sea and Mediterranean, distinct species in, 
 
 100. 
 
 ____ , saltnessof, 345. 
 
 Eeptile in old rd sandstone of Morayshire, 412. 
 Reptiles, carboniferous, 396, 897. 
 .... of lias, 322. 
 
082 
 
 IKDEX. 
 
 Reptiles, fossil eggs of, 125. 
 
 , fossil, of Nova Scotia coal, 401. 
 
 Reptilian done, great oolite, 310. 
 
 footprints in coal-strata, 399. 
 
 Retepora Jlustracea, 352. 
 
 Eetinite, or pitchstone, 474. 
 
 Ehine valley, loess of, 121. 
 
 Rhinoceros leptorliinus, tooth of, 166. 
 
 Ehynchonella spinosa, 315 ; ft. Wilsoni, 433. 
 
 Bigi, near Lucerne, conglomerate of, 179. 
 
 Riniula clathrata, great oolite, 308. 
 
 Bipple-mark, formation of, 19. 
 
 ftissoa Chastelii, eocene, 193. 
 
 Eiver-channels, ancient, 395. 
 
 Eiver, excavation through lava by, 535. 
 
 terraces, 85. 
 
 Eock, term defined, 2. 
 
 Eocks, four classes of, contemporaneous, 9. 
 
 , classification of, 90. 
 
 Eocks, composed of fossil zoophytes and shells, 
 
 , trappean, 92. 
 
 Eoderburg, extinct volcano of, 543. 
 
 Eogers, Prof. H. D., on coal-field, United States, 
 
 389. 
 
 .....cited, 393, 413, 427. 
 ...., on reptilian footprints in coal, 891. 
 . . . ., on Devonian rocks, U. S., 427. 
 , Prof. W. B., on oolitic coal-field, United 
 
 States, 330, 389. 
 
 , on Devonian rocks, U. S., 427. 
 
 Borne, formations at, 175, 580. 
 Eomer, F., on chalk in Texas, 255. 
 ftosalina, chalk, 26. 
 Eose, Prof. G., cited, 469, 557. 
 
 , on hornblende, 464. 
 
 Boss-shire, denudation in, 67. 
 Rostellaria macroptera, eocene, 218. 
 Eothliegcndes, lower, or Permian, 856. 
 Bubble, term explained, 81. 
 Eupelmonde, Upper Eocene beds, 188. 
 Eussia, erratic blocks in, 129. 
 
 . fossil meteoric iron in, 151. 
 
 ', Permian rocks in, 355. 
 
 SAAEBEUCK coal-field, reptiles found in, 397. 
 
 St. Abb's Head, curved strata near, 49. 
 
 St. Andrew's, trap-rocks in cliffs near, 556, 557. 
 
 St. Helena, basalt in, 483, 528. 
 
 St. Helens, or Osborne series, I. of Wight, 192, 
 
 210. 
 St. Lawrence, gulf of, inland beaches and cliffs, 
 
 St. Mihiel, France, inland cliffs near, 77. 
 
 St. Paul, Island of, 508. 
 
 St. Peter's Mount, Maestricht, fossils in, 237. 
 
 , sandpipes in, 83. 
 
 Salisbury Crag, altered strata of, 481. 
 Salt rock, origin of, 343. 
 
 , precipitation of, 343. 
 
 ....,atNorthwich, 343. 
 ...., lakes of Asia, 344. 
 
 Salter, Mr., on fossils of Caradoc sandstone, 
 438. 
 
 , on Caradoo beds, 438. 
 
 . . . ., on Silurian fish, 432. 
 
 , on Silurian rocks of Canada, 446. 
 
 San Lorenzo, recent strata at, 120. 
 Sandpipes near Maestricht, 83. 
 
 near Norwich, 82. 
 
 , or sandgalls, term explained, 82. 
 
 Sandstone, with cracks in Wealden, 263. 
 Sandwich Islands, coral-reef in, 241. 
 
 , volcanoes of, 489, 508, 528, 546. 
 
 Sangatte, near Calais, drift of, 288. 
 Sao Mrsuta, metamorphoses of, 450. 
 Saucats, near Bordeaux, faluns of, 178. 
 Saurians of lias, 323. 
 
 , thecodont, 355. 
 
 Saurichthys apicalis^ tooth of, 336. 
 Saussure, M., on moraines, 147. 
 ...., on vertical conglomerates, 47. 
 Savi, M., on Carrara marble, 612. 
 Samicaxa rugosa, pleistocene, 330. 
 
 Saxony, granite in, 583. 
 . Scacchi, M., on post-pliocene strata, 118. 
 Scaphites cequalis, '245 ; S, ffiaas, 258. 
 Scarborough, oolitic plants of, 314. 
 Schist, hornblende and mica, 588, 589. 
 . . . , , argillaceous, 589. 
 ...., chlorite, 589. 
 Schizodus Schlotheimi, 350; S. trwicatus. 
 
 hinge, 350. 
 
 Schorl-rock and schorly granite, 564. 
 Scoresby on icebergs, 127. 
 Scoriae, 469. 
 
 Scotland, carboniferous traps of, 556. 
 ...., northern drift in, 130. 
 
 , old red sandstone of, 414. 
 
 Scrope, Mr., cited, 305, 542, 546, 548, 550, 553, 
 
 , on globular structure of traps, 486. 
 
 ...., on Ponza Islands, 605. 
 
 , on trachyte, basalt, and tuff, 470, 522. 
 
 , on central France, 197. 
 
 Sea-cliffs, inland, 71. 
 
 Section of Wealden, 273. 
 
 , of white chalk from England to France, 
 
 239. 
 
 , of volcanic rocks, Auvergne, 547. 
 
 Sedgwick, Prof., on brecciated limestone, 351. 
 
 , on Caradoc beds, 438. 
 
 , on concretionary magnesian limestone, 87. 
 
 , on Coniston grit, 439. 
 
 . . . ., on Devonian group, 419. 
 
 , on garnets in altered rock, 480. 
 
 ...., on granite, 580, 583. 
 
 . . . ., on Permian sandstones, 354. 
 
 , on joints and cleavage, 600, 602, 609. 
 
 , on mineral composition of granite, 568. 
 
 , on old red of Devon and Cornwall, 419. 
 
 , on structure of rocks, 600. 
 
 , on trap-rocks of Cumberland, 559. 
 
 Segregation in mineral-veins, 619. 
 
 Semi-opal, infusoria in, 26. 
 
 /Seraphs convolutum. Barton clay, 213. 
 
 Serpentine, 474. 
 
 Serpula attached to Gryphcea, 22; toSpatan 
 
 gus, 23. 
 
 carbon aria, coal, 384. 
 
 Serpulce, and Bryozoa, on Encrinite, 307. 
 Serpula?, on volcanic rocks, in Sicily, 157. 
 Sewalik Hills, freshwater deposits, 182. 
 . . . . , miocene strata in, 182. 
 Shale, carbonaceous, 313. 
 
 , defined, 11. 
 
 Shales of coal near Dudley, 593. 
 
 Sharks, teeth of, 215. 
 
 Sharpe, Mr. D., on mollusca in Silurian strata, 
 
 446. 
 , . . ., on slaty cleavage, 609. 
 
 , a upper greensand, 250. 
 
 Shells, fossil, passim. 
 
 , fossil, useful in classification, 114. 
 
 . . . ., recent, 28, 29, 30, 140, 144. 
 Sheppey, Isle of, fossil flora of, 216. 
 Sherringham, mass of chalk in drift, 134. 
 Shetland, granite of, 440, 565, 568. 
 
 , hornblende-schist of, 596. 
 
 Shrewsbury, coal-deposit near, 384 
 
 Sicily, Fiume Salso in, 223. 
 
 . . . ., inland cliffs in, 74. 
 
 . . . ., newer pliocene strata of, 155. 
 
 . . . ., terraces of denudation in, 75. 
 
 Sidlaw Hills, trap of old red sandstone, 553. 
 
 Siebengebirge, igneous rocks of, 540. 
 
 Sienna, formations at, 174. 
 
 Sigillaria, 866, 368. 
 
 Sigillaria larvigata, coal, 367. 
 
 Siliceous limestone defined, 12. 
 
 rocks defined, 11. 
 
 Silliman, Prof., cited, 574. 
 Silurian, name explained, 429. 
 
 . . period, plutonic rocks of, 581. 
 
 . . rocks, table of, 430. 
 
 . . strata of deep-sea origin, 447, 
 
 . . strata of United States, 444. 
 
 . . strata, thickness of, 442. 
 
INDEX. 
 
 683 
 
 Silurian strata, foot-tracks in, 452. 
 
 volcanic rocks, 558. 
 
 Simpson, Mr., on ice-islands, 135. 
 Siphonia pyriformis, upper greensand, 249. 
 Siphonotreta unguiculata, Silurian, 444. 
 Sivatherium, extinct ruminant, 182. 
 Skapter Jokul, eruption of, 521. 
 Skye, rocks of, 481, 580. 
 
 , basaltic columns in, 4S3. 
 
 ...., dikes in Isle of, 478. 
 
 , sandstone in, 36. 
 
 Slates of Devon, cleavage of, 603. 
 
 Slaty cleavase, 602. 
 
 8lickensides~ term defined, 621. 
 
 Smith, Mr., of Jordan Hill, on pleistocene, 
 
 140. 
 
 Snags, fossil, 375. 
 
 Snakes' ggs, fossil at Tonna, near Gotha, 125. 
 Soissonnais sanda, 228. 
 Solenhofen, lithographic stone of, 302. 
 Solfatara, decomposition of rocks in the, 595. 
 Soinma, 525. 
 
 lava at, 478. 
 
 Sopwith, Mr. T., models by, 57. 
 
 Sorby, Mr., on mechanical theory of cleavage, 
 
 603, 
 
 Sortino, cave in valley of, 160. 
 South Devon and Cornwall, old red of, 419. 
 South Downs, view of, 274. 
 Sowerby, Mr. G., cited, 169. 
 Spaccoforno, inland cliffs at, 76. 
 Spain, volcanoes in, 6, 531. 
 Spalacotherium, Purbeck mammifer, 295, 457. 
 Spatangw (recent), 23 ; 8. radiatus, 233. 
 
 , with Serpula attached, 23. 
 
 Spezzia, gulf of, calcareous rocks in, 612. 
 Sphcerexochits minis, Wenlock, 436. 
 Sphcerulites agariciformis, chalk, 253. 
 Sphenopteris crenata, 361 ; S. graoilis, 264. 
 Spirifer dis/unctus, S. Verneuilii, 421; 8. 
 glaher, 8. trigonalis, 406. 
 
 mucrcnatus, 424: S. undulatus, 352: & 
 
 Walcottii, 318. 
 
 Spirolina stenostoma, eocene, 227. 
 Rpirorbis carbonariu^ coal, 3S4. 
 Spitzbergen, glaciers of, 142. 
 Spondylus spinosus, chalk, 247. 
 Sponges in chalk, 249. 
 Spongilla of Lamarck, in tripoli, 25. 
 . . . ., spicnla of, tripoli, 25. 
 Spring?, mineraL See Mineral springs, 626. 
 Staffa, basaltic columns in, 483. 
 Stauria astrceaformis, Silurian, 403. 
 
 Steno on classification of rocks, 91. 
 Sternbergia, structure of, 368. 
 Stigmaria in fossil forest, Nova Scotia, 377. 
 Stigmaria and Sigillaria, 367. 
 
 ficoides, coal, 368. 
 
 Stirling Castle, rock of, altered by dike, 481. 
 
 Stockholm, post-pliocene beds near, 119. 
 
 Stokes, Mr., on petrifaction, 43. 
 
 Stonesfield, fossil mammalia, 310, 312. 
 
 .... slate. 309. 
 
 Storton Hill, footprints at, 337. 
 
 Strata, term defined, 2. 
 
 arrangement of, determined by fossils, 21, 
 
 . . ., consolidation of, 34 
 
 . . ., curved and vertical, 47, 58. 
 
 . . , elevation of, above the sea, 44. 
 
 . . , fossiliferons, tabular view of, 104. 
 
 . . , horizontally of, 15, 45. 
 
 . . , metamorphic origin of, 596. 
 
 . . , mineral composition o 10. 
 
 . . , outcrop of, 56. 
 
 . . , tertiary classification of, 109. 
 Stratification, forms of, 13, 16, 47. 
 . . . ., unconformable, 59. 
 Strickland, Mr., on new red sandstone, 336. 
 Strike, term explained, 53. 
 Stringocephalu* Burtini. Devonian, 423. 
 Btromboli, lava of, 574. 
 
 Strophomena, depressa, 436 ; S. grandis, 440. 
 Studer, M., on Swiss Alps, 614. 
 
 Studer, M., on boulders of Jura, 149. 
 
 Stutchbury, Mr., cited, 324, 355. 
 
 Sub-Apenuine strata, 110, 173. 
 
 Subsidence in drift-period, 141. 
 
 Succinea amphibia, 29 ; S. elongata, 124. 
 
 Suffolk crag, 168. 
 
 Sullivan, Capt, chart of Falkland Islands, 88. 
 
 Superga, near Turin, tertiaries of Hill of, 179. 
 
 Superior, Lake, marl in, 36. 
 
 Superposition of aqueous deposits, 96. 
 
 Superposition of volcanic rocks, test of age, 
 
 326. 
 
 Snpracretaceons, term explained, 103. 
 Sus scrofa, tooth of, 166. 
 Sussex marble, 261. 
 Swansea, coal-measures near, 859. 
 . . . ., stems of Sigillaria at, 3T3. 
 Sweden, alum-schists of, 451. 
 Swiss Jura, structure of, 55. 
 Sydney coal-field, Cape Breton, 3SO. 
 Syenite, 564. 
 Syenitic granite, 564. 
 Synclinal line, term defined, 48. 
 
 TABLE MOTTNTAIN, strata horizontal in, 45. 
 
 , granite- veins in, 567. 
 
 Table of fossiliferous strata, 104. 
 
 Tails of homocercal and heterocercal fish, 353. 
 
 Talcose gneiss, 590. 
 
 .... granite, 564. 
 
 Tupirus Americans (recent), tooth of, 166. 
 
 Tartaret, Puy de, cone of, 548. 
 
 Teeth of mammals, fossil and recent, 165, 166, 
 
 167, 219, 233, 311, 341. 
 Tderpeton Elginense, old red, 412. 
 Tellina dbliqua, pleistocene, 155. 
 Temn4chinu8 exeavatus, coralline crag, 172 
 Teneriffe, Peak of, 509, 511. 
 Tentaculites annulatus,- Silurian, 439. 
 Terebelluin convolutum, T.fusiforme, 213. 
 Terebratvla (Atrypa) affinis, 434. 
 Mplicata, T. carnea, T. Defrancii, T. 
 
 octopttcata, T. plicatilit, T. pumilus, 246. 
 diffona,S08; T.fimbria.SW: T.hastata, 
 
 406; T.lyra,ysi. 
 navicula, 431 ; T. porrecta. 423 ; T. sella, 
 
 259; T. Wil8oni,m 
 Ttredina personata, fossil wood bored by, 
 
 Teredo navalis boring wood, 24. 
 Terra del Fnego, 145. 
 
 Fucus giganteus in, 242. 
 
 Tertiary, term explained, 109. 
 .... deposits, 178, 189, 190. 
 
 strata, tabular view of. 104. 
 
 Testudo atlas, of Sew&lik Hills, 182. 
 
 Texas, chalk in, 255. 
 
 Thames valley, freshwater deposits in, 152. 
 
 Thamnastrcea, coral-rag, 303. 
 
 Thanet sands described, 221. 
 
 Thecodont saurians, 342, 355. 
 
 Thecodontoaaurus, tooth of, 355. 
 
 Thecosmilia anniilaria, 303. 
 
 Thelodm, shagreen-scales of, 4^2. 
 
 Thirria, M., on oolitic group in France, 329. 
 
 Thuja occidentalis, in stomach of mastodon, 
 
 144. 
 
 Thurmann, M., cited, 55, 280, 308. 
 Tilestones, 430. 
 
 Tilgate Forest, remains in, 262. 
 Till, term explained, 133. 
 ...., origin of, 134. 
 Tin, veins of, in Cornwall, 620, 627. 
 Tiverton, trap-porphyry near, 555. 
 Tongrian system of M. Dumont, 1S8. 
 Touraine, faluns of, 175. 
 Trachyte, 466. 
 
 , of Hungary, 565. 
 
 Trachytic rocks, older than basalt, 522. 
 
 Transition, term explained, 91, 429. 
 
 Trap, term explained, 460. 
 
 .... dike in Fifeshire, 557. 
 
 ...., globular structure of, 486. 
 
 , intrusion of, between strata, 482. 
 
684 
 
 INDEX. 
 
 Trap, various ages of, 556, 559. 
 
 , passage of granite into, 564. 
 
 in Radnorshire, 558. 
 
 .... rocks, relation to lava, 486. 
 
 rocks, lithological character of, 522. 
 
 Trappean rocks, 91. 
 
 Trap-tuff, 470. 
 
 Trass in Lower Eifel, 474, 543. 
 
 Travertin, how deposited, 84. 
 
 Tree-ferns in Permian formation, 857. 
 
 Tree-ferns (recent). 362. 
 
 Trias, or new red sandstone, 332, 333, 335. 
 
 , in Cheshire and Lancashire, 836, 343. 
 
 , subdivisions of, 333. 
 
 Trigonellites latus, oolite, 302. 
 Trigonia caudata, 259; T. giblosa, 301. 
 Trigonocarpum olivceforme, T. ovatum, 369. 
 Trigonotreta undulata, Permian, 852. 
 Trilobites in Devonian strata, 424 
 . . . ., metamorphoses of, 444, 450. 
 
 , of lower Silurian, 441. 
 
 Triloculina inflata, eocene, 227. 
 
 Trimmer, Mr., on denudation of "Wealden, 285. 
 
 , on sand-galls, 82. 
 
 , on shells in drift near Menai Straits, 136. 
 
 Trinucleus Caractaci, T. concentricus, T. or- 
 
 natus, 441. 
 
 Trionyx, fragment of carapace of, 208. 
 Tripoli composed of infusoria, 24. 
 Trochus Anglicus, lias, 39. 
 Trophon clatkratum, pleistocene, 130. 
 Tuff, volcanic, and trap, 6, 470. 
 Tuffs on Wrekin and Caer Caradoc, 558. 
 Tuomey, Mr., cited, 234. 
 Tupaia Tana (recent), jaw of, 311. 
 Turner, Dr., cited, 41, 42. 
 Turrilites costatus, chalk, 246. 
 Turritella multisulcala, Bracklesham, 216. 
 Tuscany, volcanic rocks of, 530. 
 Tynedale fault, 64. 
 Tynemouth Cliff, limestone at, 351. 
 Typhis pungens, Barton, 213. 
 
 UDDEVALLA, post-pliocene strata at, 119. 
 ...., shells of, compared with those near Na- 
 ples, 112. 
 
 Underlying, term applied to granite, 8. 
 Ungulite grit of Russia, 443. 
 Unio littoralis (recent), 28. 
 
 , Valdensis, "Wealden, 263. 
 
 United States, coal-field of, 388. 
 
 , cretaceous formation in, 254. 
 
 . . . ., Devonian rocks of, 426. 
 
 , Devonian strata in, 426. 
 
 , eocene strata in, 231. 
 
 , older pliocene and miocene formations in, 
 
 , oolite and lias of, 330. 
 
 Silurian strata of, 444 
 
 Upper greensand, 250. 
 
 Upsala, strata containing Baltic shells near, 129. 
 
 Ural Mountains, gold of, 629. 
 
 Ursus spelceus, tooth of, 167. 
 
 VAL DI NOTO, composition of, 529. 
 . . . ., igneous rocks of. 487. 
 . . . ., inland cliffs in, 76. 
 Valleys, origin of, 70. 
 
 , transverse of Weald, 275. 
 
 Valorsine granite, 569. 
 Valvata, pleistocene, 29. 
 Veins, mineral. See Mineral veins, 618. 
 Veinstones in parallel layers, 623. 
 Velay, volcanoes of, 552. 
 Venericardia planicosta, eocene, 214 
 Venetz, M., on Alpine glaciers, 146. 
 Ventrieulites radiatux, chalk, 248. 
 Verneuil, M, de, on Devonian of the U. S., 
 
 . . ., on horizontal strata in Russia, 129. 
 . ..., on lower Silurian, U. S., 445. 
 
 , on Pentameru* Knightii, 433. 
 
 ., .., on Permian flora, 354 
 
 Vertebrata, fossil, progress of discovery of, 458. 
 
 , not found in lower Silurian, 454 
 
 Vesuvius, eruption of, 526. 
 
 Vicenza, basaltic columns near, 485. 
 
 Vidal, Capt, survey by, 495. 
 
 Vienna basin, faluns of, 179. 
 
 Virginia, U. S., fossil shells in, 181. 
 
 Virlet, M., on corrosion of rocks by gases, 595. 
 
 , on geology of Morea, 55. 
 
 , on inland cliffs, 73. 
 
 Volcanic dikes, 6, 426. 
 
 mountains, form of, 5, 4S9. 
 
 rocks, age of, 519. 
 
 . . . ., analysis of minerals in, 475. 
 
 , Cambrian, 559. 
 
 , composition and nomenclature of, 462. 
 
 , described, 5, 460. 
 
 .... of Hungary, 544. 
 
 of post-pliocene period, 523. 
 
 of "Wales, great thickness of, 444 
 
 .....Silurian, 558. 
 
 .....test of age of, 519. 
 
 .... tuff, 6, 470. 
 
 Volcanoes around Olot in Catalonia, 583. 
 
 . . . ., extinct, 6, 530, 543, 545. 
 
 .... in Spain, age of, 536. 
 
 , newer, of Eifel, 540. 
 
 .... of Auvergne, 545. 
 .... of Canaries, 494. 
 .... of Java, 492. 
 
 of Sandwich Isles, 489. 
 
 Volteia heterophylla, 335. 
 Valuta ambigua, V, atkleta, 213. 
 ...... Lamberti, crag, 172. 
 
 .... iatrella, 216 ; F. nodosa, 218. 
 
 Von Buch, Baron, cited, 470, 580, 581. 
 ...., on boulders of Jura, M9. 
 
 . . . ., on brown-coal, 191. 
 
 ...., on Canary Islands, 494. 
 
 , on Cystideae, 489. 
 
 . . . . , on land rising, 45. 
 
 WACK, or argillaceous trap, 474. 
 
 Walchia pintformis, Permian, 356. 
 
 "Wales, ancient glaciers of, 136. 
 
 Waller, quoted, 93. 
 
 Warren, Dr. J. C., on skeleton of Mastodon gi- 
 
 ganteus, 144. 
 
 Waterhouse, Mr., cited, 203, 812. 
 Watt, Mr. G., experiments on fused rocks, 528, 
 
 594. 
 
 Waves, action of, on limestone, 78. 
 Weald clay, 260. 
 
 Weald Valley, denuded at what period, 281. 
 Wealden, term explained, 259. 
 . . . ., the fracture and upheaval of, 280. 
 
 , extent of formation, 264. 
 
 , plants and animals of, 262, 265. 
 
 Webster, Mr. T., cited, 109, 293, 297. 
 
 Wellington Valley, caves in, 162. 
 
 Wener Lake, horizontal Silurian strata of, 45. 
 
 Wenlock formation, 428. 
 
 ...., shale, 437. 
 
 Werner on classification of rocks, 91. 
 
 ...., on mineral veins, 618. 
 
 , on volcanic rocks, 463. 
 
 Westerwald, igneous rocks of, 533, 540. 
 Westphalia, tertiaries of, 178. 
 Westwood, Mr., on beetles in lias, 328. 
 Whin-Sil, intrusion of trap between beds at 
 
 the, 482. 
 
 Whinstone, or trap, 474 
 White chalk, 12, 239. 
 White Mountains, granite-vein in, 574. 
 White sand of Alum Bay, 12. 
 Whitestone, or Eurite, 564. 
 Wigham, Mr., on fossils, near Norwich, 155. 
 Wolverhampton, fossil forest near, 374. 
 Wood; fossil and recent, perforated by Mol- 
 
 lusca, 24. 
 
 ...., from Colebrook Dale, structure of, 369. 
 ,from the coal, microscopic structure ef, 
 
 40. 
 
Wood, from the lias, 828. 
 
 Wood, Mr. Searles, on Antwerp crag shells, 
 
 173. 
 
 . . ., on fossils of crag, 169. 
 . . , on fossils of Isle of Wight, 211. 
 
 ., on number of shells in crag, 155. 
 . . ., on cetacea of crag, 173. 
 .. ., cited, 177. 
 Woodward, Mr., on mammoth bones, Norfolk, 
 
 153. 
 
 Woolwich beds described, 220. 
 Wrekin, trap of, 70. 
 
 INDEX. 
 
 Wyman, Dr., cited, 23$. 
 XIPHODON gracile, outline of, 225. 
 YORKSHIRE Oolite, plants of, 313. 
 
 685 
 
 ZAMIA spiralis (recent), 297. 
 Zechstein, 350. 
 
 Zeuglodon cetoides, tooth and vertebra of, 328. 
 Zoophytes, fossil, 22. 157. 182, 301, 303, 403, 404, 
 422,435." 
 
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