The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924029284381 GEOLOGY AND REVELATION. Sicut Angnstlnns docet, In hujusmodi qusestionibus duo sunt obserranda. Frimo quidem ut Veritas Scripturse inconcusse teneatur. Secundo, cum Scriptura Divina mul- tipliciter exponl posslt, quod nulU expositionl aliquis ita prsecise inhsereat, ut si certa ratione constiterit hoc ease falsnm quod aliquis sensum Scripturse esse credebat, id nihilominus asserere prsesumat ; ne Scriptura ex hoc ab infldelibuB derideatur, et ne eia via credendi praecludatur. S. Thomas, De Opere SeamdcBDiei ; Summa, Pars 1, Qosest. 68, Art. 1. As Augustine teachetb, there are two tilings to be observed in questions of this kind. First, that the truth of Scripture be inviolably maintained. Secondly, since Divine Scripture may be es-plained in many ways, that no one cling to any particular exposi- tion with such pertinacity that, if what he supposed to be the teaching of Scripture should turn out to be plainly false, he would nevertheless presume to put it fonvard ; lest thereby Sacred Scripture should be exposed to the derision of unbelievers, and the way of salvation should be closed to them. Saint Thomas, On the Work of the Second Day. GEOLOGY AND REVELATION: OS THE ANCIENT HISTORY OF THE EARTH, CONSIDERED IN THE LIGHT OP GEOLOGICAL FACTS AND REVEALED RELIGION. Wd.\i lUnstratioKS. BY THE BET. GERALD MOLLOY, D.D., PBOFESSOR OF THEOLOQY IN THE ROYAL COLLEGE OP ST. PATRICK, MAYNOOTH. LOJSTBOW: LONGMANS, GEEEN, KEADER, AND DYEB. DUBLIN; M°GLASHAN AND GILL; AND W.B. KELLY. 1870. [The right of Translation and of Beproduotimi is Bcserved.] DUBLIN : •■ Prtntetl at ti)e SSnibersitQ ^^ress, BY M. H. OILI,. TO THE VERY REVEREND CHARLES WILLIAM RUSSELL, D,D., PRESIDENT OP SAINT PATlllCR'S COLLEGE, MATNOOTH, i|ii8 Wahxmit is |nstribtt>, WITH EVERY SENTIMENT OF AFFECTION AND RESPECT. PREFACE. The progress of modern Science has given rise to not a few objections against the truths of Revelation. And of these there is none which seems to have taken such a firm hold of the public mind in England, and, indeed, throughout Europe generally, as that which is derived from the interesting and startling discoveries of Geo- logy. Accordingly, when I was engaged, some years ago, in explaining and defending the Evidences of Revealed Religion, I found myself brought face to face with Geological phenomena and Geological speculations. It was plainly impossible to consider, in a candid and philosophical spirit, the argument with which I had to deal, so long as I remained ignorant of the evidence on which it was based. I resolved, therefore, to make myself familiar with the leading principles and the leading facts of Geology. And thus I was drawn insensibly into the study of this science ; to which I have vm PKEFACE. devoted, for some years, the greater part of my leisure hours. Impressed with the conviction that no fact can be really at variance with Revealed Truth, I determined, in the first place, to ascertain the facts which have been brought to light by the researches of Geologists. The general principles, which might afterwards appear to be clearly in- volved in these facts when duly classified and arranged, I was fully prepared to admit. And I hoped, in the end, to search out and discover the harmony which, I was satisfied, must exist be- tween conclusions thus established and the In- spired Word of God. While occupied in working out this problem for myself it was suggested to me that others, who had not time or opportunity to pursue the same line of inquiry, would, perhaps, be glad to share in the fruits of my studies. In deference to this suggestion I consented, not without misgivings, to write a series of papers on Geology in its relations with Revealed Religion, which have appeared, from time to time, in the Irish Eccle- siastical Record. From the attention these papers attracted, crude and fragmentary as they were, it soon became evident that the question was PREFACE. IX not without interest for a large class of readers. And I have been led to believe that a more full and mature, but at the same time a popular, Treatise on the subject would be a welcome accession to ecclesiastical literature, and would supply a want that has long been felt. Such a Treatise I have proposed to myself in the present Volume. In Geology I wish to disclaim, at the outset, all pretension to original researches ; which my opportunities did not permit, nor the scope of my Work demand. It was not my object to en- large the bounds of Geological knowledge; but rather to ascertain what that knowledge is, and to set it before my readers in plain and simple words. For this purpose I have had recourse to the great masters of the science : and have en- deavoured to gather into a systematic form the phenomena upon which they are all agreed ; to sketch in outline the general theory about which there is practically no dispute ; and to draw out the line of reasoning by which, as it seems to me, this theory may be most effectively demon- strated. Exact references are given to the original au- PREFACE. thorities on all questions of importance, and on many points even of minor detail : partly that I might not seem to claim as my own what be- longs to others ; partly that I might consult for the convenience of those who should wish to in- vestigate more minutely what I have but lightly touched. And here it may be well to observe, with regard to the two classic works of Sir Charles Lyell, his Elements and his Principles, which have been reproduced so many times and in so many forms, that I have uniformly referred to the latest edition of each. The "Woodcuts which illustrate the Volume will, I venture to hope, help to convey a clear and distinct impression of many natural objects which can be represented but imperfectly in words. Some of the most striking and effective are taken from the admirable Manual of Geology brought out some years ago by the Reverend Doctor Haughton, of Trinity College, Dublin. My best thanks are due to the learned author for the kindness with which he placed his "Woodblocks at my disposal. I have also to express my ac- knowledgments to Sir Charles Lyell, who has allowed me to reproduce some of the drawings PREFACE. that embellish his works ; and to the eminent publishers Messrs. Bell and Daldy of London, and Mr. Nimmo of Edinburgh, who have, with great courtesy, furnished me with electrotypes of se- veral figures from the works of Doctor Mantell and Mr. Hugh Miller. To my colleagues in Maynooth I am much indebted for their judicious suggestions and friendly assistance during the progress of the Work. In particular I desire to testify my obligations to our distinguished Professor of Scripture, the Reverend Doctor M'Carthy, for the unwearied kindness with which he has allowed me to draw at pleasure on his profound and ex- tensive knowledge of the Sacred Text. G. M. Saint Pateick's Coiiege, Maynooth, December ist, 1869. CONTENTS. IHTEODUCTOKY CHAPTEE. PAGE. Scope of the Work explained — Geology looked on with Suspicion by Christiana — hailed with Triumph by Unbelievers — no Contra- diction possible between the "Works of Nature and the "Word of '^ God— Author not jealous of Progress in Geological Discoveries — Points of Contact between Geology and Eevelation— the Question ~— stated — the Answer — Division of the Work i PAET I. GEOLOGICAL THEORY AND THE EVIDENCE BY WHICH IT IS SUPPORTED. CHAPTEE I. THEOKT OF GEOLOGISTS. Geology defined — Facts and Theories — Recent Progress of Geology — Stratification of Rocks — Aqueous Eocks ; of Mechanical Origin — of Chemical Origin — of Organic Origin — Igneous Rocks, Plutonic and Volcanic — Metamorphic Rocks — Summary of the Eocks that compose the Crust of the Earth — Relative Order of Position — Internal Condition of the Globe — Movements of the Earth's Crust — Subterranean Disturbing Force — Uplifting and Bending of Strata — Denudation and its Causes — Fossil Remains — their Value in Geological Theory, . . 7 CONTENTS. CHAPTER II. THEOBT OF DENITDA.TION ILIUSTEATED BY FACTS. FAQE. Principle of Reasoning common to all the Physical Sciences — This Principle applicable to Geology — Carbonic Acid an Agent of De- nudation — Vast Quantity of Lime dissolved by the Waters of the Rhine and borne away to the German Ocean —Disintegration of Rocks by Frost — Professor TyndaJl on the Matterhorn — Running Water— its Erosive Power — an active and unceasing Agent of Denudation — Mineral Sediment carried out to Sea by the Ganges and other great Rivers — Solid Rocks undermined and worn away — Falls of the Clyde at Lanark — Excavating Power of Rivers in Auvergne and Sicily — Falls of Niagara — Transporting Power of Running Water — Floods in Scotland — Immdation in the Valley of Bagnes in Switzerland, 27 CHAPTER III. THEOET OF DENTJBATION— FTJKTHER ILLtTSIRATIONS. The Breakers of the Ocean — Caverns and Fairy Bridges of KiUcee Italy and Sicily— The Shetland Islands— East and South Coast of Britain— Tracts of Land swallowed up by the Sea— Island of Heligoland— Northstrand-Tides and Currents — South Atlantic Current— Equatorial Current— The Gulf Stream— its Course de- scribed — Examples of its Power as an Agent of Transport, . . 44 CHAPTER IV. THEOBT OF DENUDATION CONCLUDED. Glaciers — their Nature and Composition — Their unceasing Motion Powerful Agents of Denudation— Icebergs— their Number and Size — Erratic Blocks and loose Gravel spread out over Mountains, Plains, and Valleys, at the Bottom of the Sea— Characteristic Marks of moving Ice— Evidence of ancient Glacial Action — Illustrations from the Alps— from the Mountains of the Jura — Theory applied to Northern Europe— to Scotland, Wales, and Ireland— The Fact of Denudation established— Summary of the Evidence- This Fact the first Step in Geological Theory, ,6 CONTENTS. CHAPTEE V. STRATIFIED BOCKS OF MECHANIOiL ORIQIH' — IHEOEY DEVELOPED AND ItLtrSTEATED. PAGE. Formation of Stratified Eooke ascribed to the Agency of Natural Causes — This Theory supported by Facts — The Argument stated — Examples of Mechanical Eooks — Materials of which they are com- posed — Origin and History of these Materials traced out — Prooesa of Deposition — Process of Consolidation — Instances of Consolida- tion by Pressure — Consolidation perfected by Natural Cements — Curious lUustrationa — Consolidation of Sandstone in Cornwall — Arrangement of Strata explained by intermittent Action of the Agents of Denudation, 74 CHAPTEE VI. STKATlrlED EOCKS OF MECHANICAL OEieiN — PTTKTHEIl IILirSTKATIGNS. Impossible to witness the Formation of Stratified Bocks in the Depths of the Ocean— On a small Scale Examples are exhibited by Eivers emd Lakes — Alluvial Plains —their extraordinary Fertility — Great Basin of the Nile — Experiments of the Eoyal Society — The Mississippi and the Orinoco — Some Eivers fill up their own Channels — Case of the Eiver Po — Artificial Embankments — Large Tract of Alluvial Soil deposited by the Rhone in the Lake of Ge- neva — Deltas — The Delta of the Ganges and Brahmapootra — Delta of the Nile 89 CHAPTEE VII. STEATIFIED EOCKS OF CHEMICAL OEISIN. Chemical Agency employed in the Formation of Mechanical Eoeka — But some Eocka produced almost exclusively by the Action of Chemical Laws — Difference between a Mixture and a Solution— a Saturated Solution— Stalactites and Stalagmites — Fantastic Co- lumns in Limestone Caverns — The Grotto of Antiparoa in the XVI CONTENTS. PAGE. Grecian Archipelago — Wyer'e Cave in the Blue Mountains of America — Travertine Rock in Italy — Growth of Limestone in the Solfatara Lake near Tivoli — Incrustations of the Anio — Forma- tion of Travertine at the Baths of San Filippo and San Vignone, lOo CHAPTEE VIII. STKAIIFIED EOCKS OF ORGANIC ORIGIN — ILLCSTE4II0NS FROM ANIMAL LIFE. Nature of Organic Rocks — Carhonate of Lime extracted from the Sea by the Intervention of minute Animalcules — Chalk Rock — its vast Extent — supposed to be of Organic Origin — A Stratum of the same kind now growing up on the Floor of the Atlantic Ocean — Coral Reefs and Islands — ^their general Appearance — their Geographical Distribution — their Organic Origin — Structure of the Zoophyte — Various Illustrations — Agency of the Zoophyte in the Construction of Coral Book — How the sunken Reef is con- verted into an Island — and peopled with Plants and Animals — Difficulty proposed and considered — Hypothesis of Mr. Darwin — Coral Limestone in the solid Crust of the Earth, . . . 1 1 1 CHAPTEE IX. STRATIFIED ROOKS OF ORGANIC ORIGIN ULTJSTRATIONS FROM VEGETABLE LIFE. Origin of Coal — Evident Traces of Plants and Trees in Coal Mines — Coal made up of the same Elements as "Wood — Beds of Coal found resting upon Clay in which are preserved the Roots of Trees — Insensible Transition from Wood to Coal — Forest-covored Swamps — ^Accumulations of Drift Wood in Lakes and Estuaries — Peat Bogs — Beds of Lignite— Seams of pure Coal with half Carbonized Trees, some lying prostrate, some standing erect — Summary of the Argument hitherto pursued — Objection to this Argument from the Omnipotence of God — ^Answer to the Objection, . . ij8 CONTENTS. xvii CHAPTER X. FOSSIL REMAINS THE MUSEUM. FAQE. Eeoapitulation — Scope of our Argument — Theory of Stratified Eooka the Framework of Geological Science — This Theory brings Geo- logy into Contact with Eeyelation — The Line of Reasoning hitherto pursued confirmed by the Testimony of Fossil Remains — Meaning of the Word Fossil — Inexhaustible Abundance of Fossils — Various States of Preservation— Petrifaction — Experiments of Professor Gbppert — Organic Eooks afford some Insight into the Fossil World — The Eeality and Significance of Fossil Eemains must be learned from Observation — The British Museum — Colossal Skele- tons — Bones and Shells of Animals — Fossil Plants and Trees, . 156 CHAPTEE XI. FOSSII REMAINS — THE EXPIOEAIION. From the Museum to the Quarry — Fossil Fish in the Limestone Eocks of Monte Bolca — in the Quarries of Aix — in the Chalk of Sussex — The Ichthyosaurus or Fish-like Lizard — Gigantic Di- mensions of this Ancient Monster — its Predatory Habits — The Plesiosaurus — The Megatherium or great WUd Beast — History of its Discovery — the Mylodon — Profusion of Fossil Shells — Petri- fied Trees erect in the Limestone Eock of Portland — Fossil Plants of the Coal Measures — The Sigillaria — The Fern — The Calamite — The Lepidodendron — Coal Mine of TreuU — Fossil Eemiuns afford undeniable Evidence of former Animal and Vegetable Life — Their Existence cannot be accounted for by the Plastic Power of Kature — nor can it reasonably be ascribed to a Special Act of Creation, 176 CHAPTEE XII. GEOLOGICAL CHEONOLOGY PBINCIPLES OF THE SYSTEM EXPLAINED AND DEVELOPED. Significance of Fossil Eemains — Science of Palteontology — Classifi- cation of existing Animal Life — Fossil Eemains are found to fit in with this Classification — Succession of Organic Life — Time in b XVIU CONTENTS. FAOE. Geology not measured by Tears and Centuries — Suooessive Periods marked by Buccessive Forms of Life — The Geologist aims at arranging these Periods in Chronological Order — Position of the yarious Groups of Strata not sufficient for this purpose — It is accomplished chiefly through the aid of Possil Bemains — Mode of proceeding praotioally explained — Chronological Table, . . 207 CHAPTEE XIII. GEOLOGICAL CHEONOLOGT — BEMAKI8 ON THE SrCOESSION OP ORGANIC LIFE. Summary of the History of Stratified Eocks — Striking Characteristics of certain Formations — Human Eemains found x)nly in superficial Deposits — Gradual Transition fi:om the Organic Life of one Period to that of the next — Evidence in favour of this Opinion — Advance from Lower to Higher Types of Organic Life as we ascend from the Older to the more Recent Formations — Economic Value of Geological Chronology— lUustration — Search for Coal — ^the Prac- tical Man at Fault — the Geologist comes to his aid, and saves him from useless Expense, 230 CHAPTEE XIV. BUBTEHEANEAN HEAT — ITS EXISTENCE DEMONSTEATED BY FACTS. Theory of Stratified Eocks supposes Disturbances of the Earth's Crust — These Disturbances ascribed by Geologists to the Action of subterranean Heat — The Existence of Subterranean Heat, and its Power to move the Crust of the Earth, proved by direct Evidence — Supposed Igneous Origin of our Globe — EemarkaMe Increase of Temperature as we descend into the Earth's Crust — Hot Springs — ^Artesian Wells — Steam issuing from Crevices in the Earth — The Geysers of Iceland — A Glimpse at the subterranean Fires — Mount Vesuvius in 1779— Vast Extent of Volcanic Action — Ejistence of subterranean Heat an established Fact, . . 249 CHAPTEE XV. SUBTEEEANEAN HEAT — ITS PQ-WEES ILLITSTEATED BT TOLCANOS. Effects of subterranean Heat in the present Age of the World— Vast Accumulations of solid Matter from the Eruptions of Volcanos CONTENTS. XIX PAQE. Buried Cities of Pompeii and Heroulaneiun — Curious Kelios of Ro- man Life — Monte Nuovo — Eruption of Jorullo in the Province of Mexico — Sumbawa in the Indian Archipelago — Voloanoa in Ice- land — Mountain Mass of Etna the Product of Volcanic Eruptions — ^Volcanic Islands — In the Atlantic — in the Mediterranean — San- torin in the Grecian Archipelago, 263 . CHAPTER XVI. SUBTEEEANEAN HEAT — ^ITS POWEES ILLXTSTEATED BT EAETHQTTAKEB. Earthquakes and Volcauos proceed from the same common Cause — Recent Earthquakes in New Zealand — ^Vast Tracts of Land per- manently upraised — Earthquakes of Chili in the present Century — Crust of the Earth elevated — Earthquake of Cutoh in India, 1819 — Remarkable Instance of Subsidence and Upheaval — Earth- quake of Calabria, 1783 — Earthquake of Lisbon, 1755 — Great Destruction of Life and Property — Earthquake of Peru, August, 1868 — General Scene of Ruin and Devastation — Great Sea Wave — A Ship with all her Crew carried a Quarter of a Mile inland — Frequency of Earthquakes, 280 CHAPTEE XVII. SUBTEEEANEAIT HEAT — ITS POVTEES ILLTTSTEATED B1 UNDTTLA- LATIONS OF THE EAETh's CSITST. Gentle Movements of the Earth's Crust within Historic Times — Roman Roads and Temples submerged in the Bay of Baise — Temple of Jupiter Serapis — Singular Condition of its Columns — Proof of Subsidence and subsequent Upheaval — Indications of a second Subsidence now actually taking place — Gradual Upheaval of the Coast of Sweden — Summary of the Evidence adduced to estab- lish this Fact— Subsidence of the Earth's Crust on the Vest Coast of Greenland — Recapitulation, 296 XX CONTENTS. PART II. THE ANTIQUITY OF THE EAKTH CONSIDERED IN RELA- TION TO THE HISTORY OF GENESIS. CHAPTER XVIII. STATEMENT OF THE QUESTION AND EXPOSITION OF THE ATTTHOe's TTEW. PAGE. The General Principlea of Geological Theory accepted hy the Au- thor — ^These Principles plainly import the extreme Antiquity of the Earth — Illustration from the Coal, the Chalk, and the Boul- der Clay — This Conclusion not at Variance with the Inspired,.—,. History of Creation — Chronology of the Bible — Genealogies of ~-. Genesis — Date of the Creation not fixed by Moses — Progress of "^ Opinion on this Point — Cardinal Wiseman, Father Peronne, Father Pianoiani — Doctor Buckland, Doctor Chalmers, Doctor Pye Smith, Hugh Miller — Author's View explained — Charge of Rash^^ ness and Irreverence answered — Admonitions of Saint Augustine and Saint Thomas, 307 CHAPTER XIX. PIBST HYPOTHESIS ; AN INTEETAt OF INDEFINITE DITEATION BETWEEN THE CEEATION OF THE WORLD AND THE FIRST MOSAIC DAT. The Heavens and the Earth were created before the First Mosaics- Day — Objection from Exodus, xx. 9-1 1 — Answer — Interpretation ^ of the Author supported by the best Commentators — Confirmed by the Hebrew Text— The Early Fathers commonly held the th» Existence of created Matter prior to the "Work of the Six Days — Saint Basil, Saint Chrysostom, Saint Ambrose, Venerable Bede — The most eminent Doctors in the Schools concurred in this Opinion— Peter Lombard, Hugh of Saint Victor, Saint Thomas — Also Commentators and Theologians — Perrerius, Peta- CONTENTS. XXI PAQE. viua — Distinguished Names on lie other aide, A Lapide, Tostatus, Saint Augustine — The Opinion is at least not at Variance with the Voice of Tradition — This Period of created Existence may have — been of indefinite Length— And the Earth may have been fur- (^ nished then as now with countless Tribes of Plants and Animals — < Objections to this Hypothesis proposed and explained, . . 33x) CHAPTEE XX. SECOND HYPOTHESIS J THE DATS OF CRBiTION I0N9 PEBIOBS OP TIME. Diversity of Opinion among the Eaxly Fathers regarding the Days of Creation — Saint Augustiue, PMlo Judaeua, Clement of Alexandria, Origen, Saint Athanasius, Saint Eueherius, Prooopius — Albertus Magnus, Saint Thomas, Cardinal Cajetan — Inference &om these Testimonies — First Argument in favour of the popular Interpre- tation ; a Day, in the literal Sense, means a Period of Twenty- ■"" four Hours — Answer — This Word often used in Scripture for an indefinite Period — Examples from the Old and New Testament — ~" Second Argument ; the Days of Creation have an Evening and a Morning — Answer — Interpretation of Saint Augustine, Venerable Bede, and other Fathers of the Church — Third Argument ; the Reason alleged forthe Institution of the Sabbath Day — Answer — The Law of the Sabbath extended to every Seventh Tear as well as to every Seventh Day — The Seventh Day of God's Rest a long Period of indefinite Duration, 35* CHAPTEE XXI. APPLICATION OF THE SECOND HYPOTHESIS TO THE MOSAIC HISTOET OP CEEATION CONCLITSION. Summary of the Argument — Striking Coincidence between the Order of Creation as set forth in the Narrative of Moses and in ^=- the Records of Geology — Comparison illustrated and developed — "^ Scheme of Adjustment between the Periods of Geology and the --< Days of Genesis— Tabular View of this Scheme— Objections con- sidered — It is not to be regarded as an established Theory, but CONTENTS. FAQE. as aa admissible Hypothesis — Eithfir the first Hypothesis" or the second is sufficient to meet the demaads of Geology as regards the Antiquity of the Earth — Not necessary to suppose that the Saored Writer -was made acquainted with the long Ages of Geo- logical Time — He simply records faithfully that which was com- mitted to his charge — The Mosaic History of Creation stands alone, without Rivals or Competitors, 383 LIST OF ILLUSTEATIONS. 1. Granitic Eocks off the Shetland Islands, 47 2. Iceherg seen in mid ocean, 1400 miles jrom land, .... 61 3. Block of liimestolae Eock with Glacial markings, .... 64 4> S> ^i 7> *■ Examples of living Zoophytes : Campanularia Gelatinosa ; Gorgonia Fatula, . . 127 Frustra Pilosa ; Madrepora Plantaginea, . . . 12S Corallium Euhrum, 129 9, 10. Fossil Ferns from the Coal Measures, 149 1 1. Trunk and roots of a forest tree ; found erect in a Coal Mine, near Liverpool 151 12. Fossil Irish Deer, 165 13. Fossil Wood, showing the rings of annual growth, . . . 174 14. 15. Fossil Fish from Monte Boloa in Italy, .... 177, 178 16. Group of several Fossil Fish iu one block of Limestone, . . 180 17. Fossil Fish from the Chalk Eock of Sussex, 181 18. 19. Two Skeletons ofthe Ichthyosaurus, from the Lias of Dorset- shire, preserved in the Museum of Trinity College, Dublin, 183 20. Plesiosaurus Cramptonii, from the Lias of Yorkshire, preserved in the Museum of the Eoyal Dublin Society, . . . . 187 21. The Megatherium or Great Wild Beast, 191 22. The Mylodon Eobustus, 192 23. Section of a Quarry in the Jsland of Portland, showing the stumps of an ancient forest standing erect in the solid rock, 195 24. Calamite from the Coal Measures of Newcastle 198 25. Lepidodendron Stembergii; a forest tree erect in a Coal Mine, 199 26 Lepidodendron Elegans ; Stem and branches, from a Coal Mine, neai- Newcastle, j^g CONTENTS. XXIU PAGE. 27. Section of a Goal Mine near Lyons, showing an ancient forest enveloped in Sandstone, zoi 28. Bird's-eye View of Santorin during the volcanic eruption of 1866 277 LIST OF TABLES. Table of Stratified Eocks Chronologically arranged, . . . . 223 Table of Geological Formations, showing the first appearance on the Earth of the various forms of Animal Life, 241 Table exhibiting the Genealogies of Genesis according to the various Headings of the three most ancient Versions, the Hebrew, the Samaritan, and the Septuagint, 320 Table representing a possible Adjustment of the Mosaic Days with the Periods of Geology, 39^ GEOLOGY AND REVELATION. INTRODUCTORY CHAPTER. SCOPE OF THE WOKK EXPLAINED— GEOLOGY LOOKED ON WITH GUS- PICION BY CHRISTIANS — HAILED WITH TRIUMPH BY UNBELIEVEKS — NO CONTRADICTION POSSIBLE BETWEEN THE WORKS OP NATURE AND THE WORD OP GOD — AUTHOR NOT JEALOUS OP PROGRESS IN GEOLO- GICAL DISCOVERIES —POINTS OP CONTACT BETWEEN GEOLOGY AND REVELATION— THE QUESTION STATED — THE ANSWER — DIVISION OP THE WORK. Among the various pursuits that engage the human mind there are few so attractive as Geology, none so important as Revelation. Each of these two studies has an interest peculiar to itself. The one is chiefly con- cerned about the world in which we are living : the other about the world to which we are hastening. Ge- ology leads us down into the depths of the Earth, and there, unfolding to our view a long series of strange unwritten records impressed on lasting monuments by the hand of Nature, it proceeds to trace back the history of our Globe through myriads of ages into the distant past. Revelation, on the other hand, comes to us from above ; and setting forth the far more won- derful records of God's dealings with man, holds out B SCOPE OF THE WORK. the hope of another world " everlasting in the heavens" ' which shall still remain when this earth and all the works that are therein shall have melted away with fer- vent heat.' But, it may be asked, why should two such incongru- ous topics he set down for discussion side by side? To answer this question is to explain the scope and design of the present work. We are not going to write a Manual of Geology ; nor yet a Treatise on Eevela- tion. Taken separately these two subjects have been handled with eminent skill and ability ; the one by the votaries of Science, the other by the friends of Theology. It is our purpose to consider them not so much in themselves as in their mutual relations : to compare the conclusions of Geology with the truths of Revela- tion ; and to inquire if it be possible to accept the one and yet not to abandon the other. "An uneasy apprehension has long prevailed among devout Christians, and a declared conviction among a large class of unbelievers, that the discoveries of Ge- ology are at variance with the facts recorded in the Book of Genesis. Now the. historical narrative of Ge- nesis lies at the very foundation of all Eevealed Re- ligion. Hence the science of Geology has come to be looked on with suspicion by the simple-minded faithful, and to be hailed with joy, as a new and powerful auxiliary, by that infidel party which in these latter days has assumed a position so bold and defiant. It is 1 II. Cor. vi. .. s n. Pet. iii. lo. THE TWO RECORDS 3 now confidently asserted that we cannot uphold the teaching of Revelation unless we shut our eyes to the evidence of Geology ; and that we cannot pursue the study of Geology if we are not prepared to renounce our belief in the doctrines of Revelation. Yet surely this cannot be. Truth cannot be at va- riance with truth. If God has recorded the history of our Globe, as Geologists maintain, on imperishable monuments within the Crust of the Earth, we may be quite sure He has not contradicted that Record in His Written Word, There may be for a time, indeed, a con- flict between the student of Nature and the student of Revelation. Each is liable to error when he under- takes to interpret the record that is placed in his hands. Many a brilliant Geological theory, received at first with unbounded applause, has been dissipated by the progress of discovery even within the life-time of its author. On the other hand it cannot be denied that Theolo- gians have sometimes imputed to the Bible that which the Bible does not teach. Learned and pious men — Protestants and Catholics alike — once believed that the book of Josue represents the succession of day and night as produced by the revolution of the Sun around the Earth : whereas it is now considered quite plain that the book of Josue, properly understood, teaches nothing of the kind; but that the Inspired Writer, in describing a wonderful phenomenon of Nature, simply employs the language of men according to the es- tablished usage of his time. We need not wonder, therefore, that a conflict of opinion should sometimes B 2 TWO POINTS OF CONTACT arise between the Geologist and the Theologian : but a conflict there cannot be between the story which God has inscribed on His works and the story he has recorded in His Written Word. Though we come forward, therefore, among those whose duty and whose glory it is to uphold Kevelation, we are by no means jealous of the wonderful ardour, and we may add, the wonderful success, with which the study of Geology has been lately pursued. We have too much confidence in the truth of our cause to appre- hend that it can suffer in any way from the progress of Natural Science. It is our conviction rather that the more thoroughly the works of Nature are understood the more perfectly they will be found to harmonize with the truths of Revelation. We are not afraid, therefore, to venture into the realms of Geology and to come face to face with its discoveries. Too long, perhaps, has this interesting and popular science been neglected by those who are ranged under the banner of Religion. Let it be ours to show that the study of God's works is not in- compatible with the belief in God's Word ; and that it is quite possible to investigate the ancient history of the world we inhabit without forfeiting our right to a better. The points of contact between Geology and Revela- lation are chiefly these two : — First, the Antiquity of the Earth ; Secondly, the Antiquity of the Human Race. In the present Volume we shall confine our attention to the Antiquity of the Earth. The subject that offers itself for discussion may be stated in a few words. Cgco- BETWEEN GEOLOGY AND REVELATION. legists maintain that the Crust of the Earth has been slowly built up by means of a long series of operations which would require hundreds of thousands, perhaps millions, of years for their accomplishment : whereas the Bible narrative, it is alleged, allows but the short lapse of six or eight thousand years from the creation of the world to the present time. The Geological record, then, seems to contradict the Mosaic : and the question is how this apparent contradiction is to be explained. Some have ventured to solve the problem by rejecting the historical narrative of the Bible : others by ignoring the plain facts of Geology. But there is a third class of writers, including many names of the highest emi- nence and authority, who contend that we may admit the extreme Antiquity of our Globe, which Geology so imperatively demands, without compromising in the smallest degree the truthfulness of the Mosaic story. They say that the Chronology of the Bible stops short with Adam, and does not go back to the beginning of the world. By means of the data which the Bible supplies we may calculate, at least roughly, the lapse of time from the Creation of Adam to the Birth of Christ. But from the first beginning of all created things, when God made the Heavens and the Earth, to the close of the Sixth Day when Adam was introduced upon the scene, that is an interval which in the Bible narrative is left altogether undefined and uncertain.^_JThis is the view which we hope to develop and to illustrate in the course of the following pages. Our task naturally divides itself into two parts. First DIVISION OF THE WOKK. it will be our duty to consider the received theory of Geology and to examine in detail some of the interesting and wonderful phenomena on which it is founded. This course of investigation, while it is plainly indispensable for the intelligent appreciation of our subject, cannot fail at the same time to unfold many new and striking views of the Power, and the Goodness, and the Provi- dence of God. " For the invisible things of Him from the creation of the world are clearly seen, being under- stood by the things that are made ; even His Eternal power and Godhead."' In the Second Part we shall consider the Antiquity of the Earth in reference to the History of Genesis. It will be our purpose to show that, as far as the Bible nar- rative is concerned, an interval of counties^ ages may have elapsed between the first creation of the Heavens and the Earth and the beginning of the Six Mosaic Days. Furthermore we shall contend that, without any preju- dice to the Sacred History, we may sixppose these Days themselves to have been, not days in the ordinary sense of the word, but long and indefinite Periods of Time. If we succeed in establishing these views it will be ob- vious to infer that, while the Bible enables us to deter- mine, at least by approximation, the Age of the Human Race, it allows time without limit for the past history of the Earth. ' Eom, i. 1 8. PART I. GEOLOGICAL THEORY AND THE EVIDENCE BY WHICH IT IS SUPPORTED. CHAPTER I. THEORY OF GEOLOGISTS. OEOLOQY DEFINED — PACTS AND THEOKIES — KEOEMT PKOQRESS OF GEOLOQY — STBATIFIOATION OP R0CK8 — AttnEOUS KOOKS ; OP ME- CHANICAL ORIGIN — OF CHEMICAL ORIGIN — OF ORGANIC ORIGIN — IGNEOUS BOCKS, PLDTONIO AND VOLCANIC — METAMORPHIC ROCKS — SUMMARY OP THE ROCKS THAT COMPOSE THE CRUST OP THE EARTH — RELATIVE flIlDER OP POSITION — INTERlfAL CONDITION OP THE GLOBE — MOVEMENTS OP THE EARTH'S CRUST — SUBTERRANEAN DISTURBING FORCE — UPLIFTING AND BENDING OP STRATA — ^DENUDATION AND ITS CAUSES — POSSIL REMAINS — THEIR VALUE IN GEOLOGICAL THEORY. The object of Geology is to examine and record the appearances presented by the Grust of the Earth ; and by the aid of these appearances, to trace out the long series of events by which it has been brought into its present condition. Geology, therefore, like all other natural sciences, is made up partly of fact, and partly of theory. It belongs to the Geologist first to investigate the phe- nomena which the Crust of the Earth exhibits to the eye. For this purpose he descends into the mine and the quarry ; he visits the lofty cliif by the sea-shore, the deep ravine on the mountain side, the cutting of a rail- way ; in a word, every spot where a section of the Earth's FACTS THE BASIS OF GEOLOGY. Crust is exposed to view, either by the action of Nature or by the hand of man. He then retires into the silence of his closet, with his note book and his specimens ; and there, having arranged and classified the vaiious pheno- mena which he has already examined with his eyes in the outer world, he proceeds to make his deductions, and to build up his theory. He seeks to explain how materials, so diverse in their composition, have come to be piled up together, with such admirable order, and yet with such endless variety ; and how the solid rocks have come to be the repository of petrified trees and plants and bones and shells, which seem, as it were, to start up from their graves, and to tell strange stories of a bygone world. In the early days of Geology there were compara- tively few who devoted themselves with patient industry to the collection and classification of facts : while the number was legion of those who, with a verj' meagre knowledge of facts, set themselves to build up systems. A vast multitude of difierent and conflicting theories were, in this way, brought into existence, and attracted for a time much public attention, each one being vehe- mently defended by its friends and as vehemently as- sailed by its enemies. These theories resting on no solid foundation could not hold their ground against the ad- vancing tide of new discoveries. They flourished for a brief space, and then gave way to others scarcely more substantial, which were destined in their turn to be like- wise rejected and forgotten. Thus it came to pass, from the manifest instability of its principles, that Geology ERRORS OF GEOLOGY. was long held in light repute, and practical men set little store by its boasted discoveries and startling revela- tions. But it would be unjust and unphilosophical to con- demn the modern theory of Geologists because of their past errors. We must judge of this science, not accord- ing to what it once was in the feebleness of its infancy, but according to what it now is in the growing strength of its mature years. It seems to be in the nature of things that groundless speculations and wild conjectures go before, and sober Science follows in their wake. The visionary dreams of the Alchemist led the way to the science of Chemistry, and the idle fancies of the Astro- logist have given place to the marvellous discoveries of Astronomy. So, too, amidst the confused mass of conflict- ing arguments and opinions, by which the phenomena of Geology were for a long time enveloped and obscured, the seeds of a new science were slowly germinating. New facts were eagerly sought after to support or to im- pugn the favourite theory of the hour ; and though theory after theory passed away yet the facts remained. In course of time this accumulation of facts became broad and deep and solid enough to form a sound basis for inductive reasoning : and thus almost within our own days Geology may be fairly said to have assumed the rank and dignity of a science. During the last quarter of a century it has been studied with a more ardent enthusiasm than, perhaps, any other science, in England, in France, in Germany, and in America It has been studied, too, upon better princi- EVIDENCE OF STEATIFICATION. pies than before : less attention has been paid to the building up of theories, and far more pains and labour have been expended on the careful investigation of na- tural phenomena. There are still, no doubt, different schools of Geologists which are divided among them- selves as regards many important details of theory; but there are some general conclusions upon which all Geo- logists are substantially agreed, and which, they assure us, are established by evidence that is absolutely irre- sistible. It is to these conclusions we wish to invite the attention of our readers ; for they bear very closely on the question of the Antiquity of the Earth. Geologists tell us, then, that the materials of which the Earth's Crust is composed, are not heaped together in a confused mass, but are disposed with evident marks of definite and systematic arrangement. This is an im- portant truth, of which many examples are familiar to us all, though perhaps we do not all attend to their sig- nificance. Thus in a quarry, we see commonly enough first a bed of limestone, then above that a bed of gravel, and higher still a bed of clay : and even the limestone itself is not usually a compact mass, but is arranged in successive layers, something like the successive courses of masonry in a building. Now it appears that a very large proportion of the Earth's Crust is made up in this way of successive layers, or strata, as they are called by Geologists. These strata are composed of various sub- stances, such as clay, chalk, sand, lime, and coal ; and they present everywhere the same general appearances. They are known under the common name of Aqueous ROCKS OF MECHANICAL ORIGIN. 1 1 Kocks,' because it is believed that they were originally formed under water : and here it is that the professors of Geology first come into collision with the popular no- tions that formerly prevailed. They hold that these stratified rocks were not arranged as we see them now, when the Earth first came from the hands of its Creator, but have been formed, during the lapse of unnumbered ages, by the operation of na- tural causes. Nay more, they have divided the rocks into sundry classes, and they undertake to explain the particular process by which each several variety has been produced. First in order and importance are those which derive their existence from the mechanical force of moving water. The materials of which they are com- posed first existed in the form of minute particles, which were transported by the action of water from one place to another ; then they were spread out over a given surface, just as we now see layers of sand, or mud, or ' It may be useful once for all to inform the reader that the term Mook is employed by Geologists in a technical sense. It is applied to every large msias of mineral matter that goes to form the Crust of the Earth, whether it be hard and strong, or soft and plastic. Thus, for example, gravel and clay, coal and slate, are called Soeka, just as well as limestone and granite. "Our older writers endeavoured to avoid offering such violence to our language, by spealdng of the component materials of the Earth as consisting of rooks 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 Fjench, rocca in Italian, aa^felsart in German. The beginner, however, must constantly bear in mind, that the term rook by no means implies that a mineral mass is in an indurated or stony condition."— Lyell's Elements of Geology, p. 4- I 2 KOCKS OF CHEMICAL ORIGIN. gravel, deposited near the mouths of rivers, or in the estuaries of the sea, or even upon the land itself during temporary inundations. Lastly, after a long interval came the slow but certain process of consolidation. The fine sand was cemented together and became sandstone ; the loose gravel by a similar process was transformed into a solid mass, known by the name of Conglomerate or Pudding-stone ; while the soft mud by simple pressure was converted into a kind of slaty clay, called Shale. Thus from age to age Nature was ever building up new strata, and consolidating the old. Next in order are the Aqueous Kocks which owe their origin to the agency of chemical laws. To this class be- long many of our limestone formations. Large quanti- ties of carbonate of lime are held in solution by water charged with carbonic acid gas : when the carbonic acid, in course of time, passes off the carbonate of lime can no longer be held in solution, and it is accordingly precipi- tated in a solid form to the bottom. In this manner was formed that peculiar kind of limestone called Traver- tine, which abounds in Italy, and which is well known to all who have visited Rome, as the stone of which the Gohseum was built. A still more familiar example, on a small scale, is seen in the case of Stalactites and Sta- lagmites. Water saturated with carbonic acid trickles down the sides, or drops from the roof of a limestone cavern. In its course it dissolves carbonate of lime, and holds it in solution ; afterwards, reaching the floor of the cavern, it slowly evaporates and leaves behind it a thin sheet of limestone which is called a Stalagmite ; ROOKS OF ORGANIC ORIGIN. I 3 while the icicle-like pendants that are formed by a similar process, on the roof of the cavern, are called Stalactites. There is a third class of Aqueous Rocks which are supposed to be made up almost exclusively of the frag- mentary remains of plants and animals, and are therefore called Organic. The well-known coral reefs, so dreaded by the sailor in tropical seas, are believed to be no- thing more than a mass of stony skeletons belonging to the minute marine animalcules known among zoologists as Polyps or Zoophytes. These little creatures, exist- ing together in countless multitudes, extract carbonate of lime from the waters of the ocean in which they dwell, and by the action of their living organs, convert it into a solid frame or skeleton, which is called coral. From generation to generation the same process has been going on during the long succession of Geological ages ; and huge masses of coral rock, hundreds of miles in length, have thus been slowly built up from fathomless depths of the ocean to within a few feet of its surface. Our vast coal formations, on the other hand, afford a ready example of rocks which are chiefly composed of vegetable remains. So much for the Aqueous or Stratified Rocks. Geo- logy next brings before us another and a very different group, of which the origin is ascribed to fire, and which are consequently designated by the title of Igneous Rocks. In their general appearance they are chiefly distinguished from the former by the absence of regular stratification : but they are, nevertheless, intersected by numerous planes of division, or joints, as they are called, 14 IGNEOUS AND METAMOEPHIC ROCKS. and thus divided into blocks of various size and form. Geologists believe that these rocks were at one time re- duced to a molten state by the action of intense heat, and afterwards allowed slowly to cool and to crystallize. They are divided into two classes, the Plutonic and the Volcanic. The Plutonic rocks are chiefly granite of some kind or another ; and, though they now often appear at the surface, they are supposed to have been produced originally at a considerable depth within the crust of the Earth, " or sometimes, perhaps, under a certain weight of incumbent ocean.'" The Volcanic rocks have been formed at or near the surface of the Earth, and, as the name implies, they are usually ejected, in a state of fu- sion, from the fissures of an active volcano ; though not unfrequently they assume the more imposing form of basaltic columns, as at the Giant's Causeway in Ireland, or on the island of Staffa near the coast of Argyleshire in Scotland. One group of rocks yet remains to be noticed. They have been called by various names at different times, but are now generally designated by the term Metamor- phic. In some respects they resemble the Aqueous Kocks, while, in others, they are more nearly allied to the Igneous. Like the former, they are stratified in their outward arrangement ; like the latter, they are more or less crystalline in their internal texture. As to their origin, we are told that they were first deposited under water like the Aqueous Eocks, and that afterwards their internal structure was altered by the agency of ' Lyell's Elements of Geology, p. 7. GENERAL SUMMARY. 'S subterranean heat. Hence the name Metamorphic, first suggested by Sir Charles Lyell, which conveys the idea that these rocks have undergone a change of form. To this group belong many varieties of slate, and also the far-famed statuary marble of Italy. Our readers will perceive from this brief outline that, if we follow the theory of Geologists, the rocks which compose the crust of the Earth may be conveniently divided, according to their origin, into three leading groups, the Aqueous, the Igneous, and the Metamorphic. The Aqueous are formed under water, either by the mechanical force of the water itself when in motion, or by the agency of chemical laws, or by the intervention of organic life. Hence they are naturally subdivided into three classes, the Mechanical, the Chemical, the. Organic. The Igneous Rooks are produced by heat, being first melted and then allowed to cool. When this process takes place under great pressure in the depths of the Earth, the result is granite ; and the granite Rocks are called Plutonic : when near the surface, through the agency of a volcano, the rocks so formed are called Volcanic. Lastly, the Metamorphic rocks are nothing else than Aqueous rocks, of which the texture has been altered by the action of intense heat. As regards the relative order of position amongst these various classes of rocks, the lowest place seems uniformly to belong to the granitic or Plutonic group. It is true that the granite will often appear at the sur- face of the Earth ; but wherever there is a series of rocks piled one above the other, the granite will always be the 1 6 RELATIVE POSITION OF BOCKS. lowest. This assertion is based on two broad facts : first, whenever we get to the bottom of the other rocks, they are always found to rest on granite ; and secondly, no other rock has ever yet been found beneath it. From this circumstance granite is conceived to be the solid foun- dation of the Earth's crust, and so is often called fun- damental granite. Above the granite the Aqueous Kocks have been slowly spread out layer by layer during the long lapse of ages, now in this part of the world, now in that, according as each in its turn was exposed to the action of water. The Volcanic rocks do not occur in any fixed order of succession. They are distributed irregularly over almost every country of the globe, occurring sometimes in the form of cone-shaped moun- tains, sometimes in the form of stately pillars, and some- times in the form of massive solid walls, called Dykes, forced right through the softer Aqueous Rocks, which were deposited on the surface of the Earth before the eruption. As to the Metamorphic Rocks, which are supposed to owe their peculiar character to the contact of molten mineral matter, wherever they occur, they are found in the immediate neighbourhood of some Igneous Rock. The condition of the Earth beneath its thin external crust has never been the subject of direct observation ; for Geologists have never yet been able to penetrate below the granite rocks. Nevertheless, this subject has been often discussed, and has offered a wide field for philosophical speculation. Upon one point all are agreed, that within the Crust of the Earth an intense heat very SUBTEKEANEAN HEAT. 1 7 generally prevails ; — a heat so intense that it would be quite sufficient, acting under ordinary circumstances, to reduce all known rocks to a state of igneous fusion. Hence it was a common opinion among the older Geo- logists that the condition of our globe is that of a vast central nucleus composed of molten mineral, and covered over with a comparatively thin external shell of solid rock. The most eminent Geologists, however, of the present day, hesitate to accept this opinion. They ob- serve : (i) That we have not yet learned what the material is of which the interior of the Earth is com- posed ; therefore we cannot tell for certain what degree of heat is sufficient to reduce that material to a liquid state. (2) It ia uncertain how far the immense pressure at great depths may operate to keep matter in a solid state, even when raised to a very high degree of tempe- rature. (3) There are certain astronomical and physical difficulties involved in this theory, which have not yet been fully cleared up. Modern Geologists, therefore, proceeding with more caution than their predecessors, while they regard the opinion as probable, refuse to set it down as conclusively demonstrated. But, that a very high temperature prevails in the interior of our globe, is a conclusion, they say, which is estabhshed by abun- dant evidence, and which may be regarded as morally certain. It may be asked how the various strata of Aqueous Eocks, which constitute the chief portion of the Earth's Crust, have been lifted up above the level of the sea : for, according to our theory, they were all first deposited C ■ 1 8 UPHEAVAL AND SUBSIDENCE under water. This is a question that must inevitably occur to the mind of every reader, and Geologists are ready with an answer. They tell us that from the earliest ages the Crust of the Earth has been subject to disturbance and dislocation. At various times and in various places it was upheaved, and what had been be- fore the bed of the ocean became dry land ; again it sunk below its former level, and what had been before dry land became the bed of the ocean. Thus, in the former case a new stratum which had been deposited at the bottom of the sea, with all its varied remains of a bygone age, was converted for a season into the surface of the Earth, and became the theatre of ani- mal and vegetable life : while in the latter case, the old surface of the Earth with its countless tribes of ani- mals and plants, — Ais fauna axidflora as they are called, — was submerged beneath the waters, there to receive in its turn the broken up fragnients of a former world, de- posited in the form of mud, or sand, or pebbles, or minute particles of lime. Nor is this all ; it is • but a single link in the chain of Geological chronology. We are asked to believe that, in many parts of the globe, this upward and downward movement has been going on alternately for unnumbered ages ; so that the very same spot which was first the bed of the ocean, was afterwards dry land, then the bottom of an estuary or mland lake, then perhaps once more the floor of the sea, and then dry land again : and furthermore we are assured that, while it remained in each one of these various con- ditions, thousands and thousands of years may have rolled away. OF THE EARTH S CRUST. 19 But from what source does that mighty power come which can thus upheave the solid Earth, and banish the ocean from its bed ? We are told in reply that this giant power dwells in the interior of the Earth itself, and is no other than the subterranean heat of which we have already spoken. This vast internal fire acts with unequal force upon different parts of the shell or Crust of the Earth, uplifting it in one place, and in another allowing it to subside. Now it is violent and convulsive, bursting asunder the solid rocks, and shaking the foun- dations of the hills : again it is gentle and harmless, up- heaving vast continents with a scarcely perceptible un- dulation, not unlike the long, silent swell of the ocean. So it has been from the beginning, and so it is found to be even now, in this last age of the Geological Calendar. For even within historic times mountains have been suddenly upheaved from the level plain ; and many parts of the Earth's Crust have been subject to a slow wave-like movement, rising here and subsiding there, at the rate of perhaps a few feet in a century. Some- times, too, the fiery liquid itself has burst its barriers, and poured its destructive streams of molten rock far down into the peaceful, smiling valleys. This theory of an internal disturbing force, which from time to time produces elevations and depressions of the Earth's Crust, serves to explain another pheno- menon, that cannot fail to have struck even the least observant eye. The Aqueous Rocks of mechanical formation are said to have been composed of minute fragments, which were first held suspended in water, c 2 20 DISTURBANCE OF STRATA. and afterwards fell to the bottom. If this be true, it follows that these rocks, in the first period of their existence, must have been arranged in beds parallel to the horizoji, or nearly so. But we now find them, as everybody knows, in a great variety of positions : some- times they are parallel to the horizon, sometimes inclined to it, sometimes at right angles to it ; sometimes, too, they are broken right across, sometimes curved and twisted after a very fantastic fashion. Now, all these appearances are the natural results of an upheaving force acting irregularly from below on the solid shell of the Earth. When the subterranean fire is brought to bear equally at the same time on a broad extent of sur- face, then the overlying strata are bodily lifted up, and preserve their horizontal position. But when the whole force acts with local intensity on a very contracted area, then, at that particular spot, the rocks above will be tilted up, and their position entirely changed. Sometimes they will be only bent and crushed together, sometimes dislocated and turned over ; sometimes, perhaps, a mountain will be formed, and the rocks before parallel to the horizon, will afterwards remain parallel to the slopes of the mountain. There is another process known by the name of De- nudation, which we cannot pass over in silence, for it occupies a very important place in the Natural History of our globe. Since time first began Denudation has been ever going on at the surface of the Earth, and it has left its mark more or less distinctly upon every group of rocks, from the lowest to the highest. It in- PROCESS OF DENUDATION. 2 1 eludes all the various operations by which the old existing rocks are broken up into fragments, or ground into powder, or worn away by friction, or dissolved by chemical action, and then transported from their former site to become the elements of new strata. Hence the name Denudation ; since by these operations the former surface of the Earth is carried away and a surface before covered is laid bare. The amount of destruction effected by this process in each successive age is always equal to the bulk of Aqueous Rocks formed within the same time. This wiU be at once understood when we re- member that the Aqueous Rocks are produced, for the most part, by the deposition of sediment ; and sediment is nothing else than the fragments, more or less minute, of pre-existing rocks. What is deposited on the bed of the ocean has been taken from the surface of the land ; and the new strata are built up from the ruins of the old, When we see a great building of stone towering aloft to the sky, we are certain that somewhere else on the Earth a quarry has been opened, and that the amount of excavation in the quarry is exactly represented by the bulk of solid masonry in the building. Just in the same way, the mass of Aqueous Rocks is at once the monument and the measure of previous Denudation. The process of Denudation is the work of many and various natural causes. Heat and cold, rain, hail, and snow, chemical affinities, the atmosphere itself, all have a share in it ; but the largest share belongs to the me- chanical action of moving water. Every little rill that flows down the mountain side is charged with finely- 22 DENUDATION. powdered sediment which it is ever wearing away from the surface ofitsownbed. Every great stream, besides the immense quantities of mud and sand which in times of flood it carries along in its turbulent course, has its channel strewn over with pebbles at which it never ceases to work, rounding off the angles and polishing the surfaces ; and these pebbles, what are they but the fragments of old rocks and the elements of new, — the rubble-stone of Nature's edifice on its way from the quarry to the building ? Then there are those mighty rivers, such as the Amazon, the Orinoco, the Mississippi, the Nile, the Ganges, discharging into the sea day by day their vast freight of mineral matter, millions of cu- bic feet in bulk, and thousands upon thousands of tons in weight. Often this ponderous volume of mud or sand is carried far out to sea by the action of currents, but sometimes it is deposited near the shore, forming what is called a Delta, and exhibiting an admirable example of stratified rock in the earliest stage of its existence. Lastly we have to notice the giant power of the great ocean itself, acting with untiring energies on the coasts of continents and islands all over the world, excavating the undermining cliffs, rolling huge rocks hither and thither, and spreading out the divided fragments in a new order at the bottom of the sea. To apprehend fully the magnitude of the effects which may fairly be ascribed to this last mentioned power, we must remember that, according to Geological theory, almost every portion of the Earth's crust has been more than once lifted up above the surface of the ocean, and BURIED RELICS OF THK PAST. afterwards depressed below it. It is believed that this alternate rising and sinking was effected very often, perhaps most commonly, not by sudden convulsions, but rather by slow or gradual movements. Now, during this process, as the land was emerging from the waters or sinking beneath them, new surfaces would be presented in each succeeding century to the force of the ocean currents and the erosive action of the breakers : and it is not difficult to conceive that the accumulated ruins produced, in a long lapse of time, by destructive agents so powerful, so untiring, so universal, may have readily furnished the materials for a very large proportion of the Aqueous Rocks now in existence. Hitherto we have considered the Crust of the Earth as a great structure slowly reared up by the hand of Nature ; we have spoken of the rocks that compose it, of their origin and history, of the order in which they are disposed, and of the various agencies that have been at work to mould them into their present form and feature. We have now to contemplate this marvellous structure under a new aspect ; for we are told by Geo- logists that it is a vast sepulchre, within which lie en- tombed the remains of life that has long since passed away. Each series of strata is but a new range of tombs ; and each tomb has a story of its own. Here a gigantic monster is disclosed to view, compaj:ed to which the largest beast that now roams through the forest is puny in form and contemptible in strength : there, within a narrow space, millions of minute animal frames are found closely compacted together, each so small that its exist- 24 VALUE AND SIGNIFICANCE ence can be detected only by the aid of a powerful microscope. In one place whole skeletons are found almost entire, imbedded in the bosom of the solid rock; in another, we have a boundless profusion of bones and shells ; and again in another, neither the skeleton itself appears, nor yet its scattered bones, but simply the im- print of footsteps once left upon the sandy beach, and still remaining engraved on the stone into which the fine sand has been converted chiefly by the agency of pres- sure. There is no scarcity of relics in this wonderful charnel-house of Nature. For half a century the work of plunder has been going on without relaxation or re- morse ; the tombs have been yielding up their dead ; every city in the civilized world has fiUed its museums, and the cabinets of private collectors are overflowing : but the spoils that have hitherto been carried away seem to bear a very small proportion to those which yet re- main behind. These remains of animals and plants imbedded in the crust of the Earth are called Fossils ; and Geologists maintain that the Fossils preserved in each group of strata represent the animals and plants that flourished on the surface of the Earth, or in the waters of the ocean, when that group of strata was in process of formation. There they lived, and there they died, and there they were buried, in the sand, or the shingle, or the mud that came down from the waters above. Their descendants, however, still lived on, and new forms of life were called into being by the voice of the Omnipotent Creator, making, as it were, a connecting link between the new OF FOSSIL REMAINS. 25 age of the world that was coming in and the old one that was passing away. But they too died and found a tomb beneath the waters ; for Nature, with unexhausted energies, was still busy collecting materials from the old rocks, and building up the new. And so that age passed away like the former, and another came ; and every age was represented by its own group of strata ; and each group of strata was, in its turn, covered over with a new deposit ; and the tombs were all sealed up, with their countless legions of dead, their massive monuments of stone, their strange hieroglyphic inscriptions. At length came the last stage of the world's history, and man ap- peared upon the scene ; and it is his privilege to descend into this wonderful sepulchre, and to wander about amidst the monuments, and to strive to read the in- scriptions. In our own days more especially, eager and enthusiastic students are abroad over the whole face of the globe, and are gathering together from every country the Fossil Eemains of extinct worlds. By the aid of Natural History they seek to assign to each its own proper place in the ranks of creation ; to trace the rise, the progress, and the extinction, of every species in its turn ; and even to describe the nature and the character of all the various forms of life that have dwelt upon the Earth from the beginning. Such is the theory of Geology as expounded at the present day by its most able and popular advocates. We have passed over a multitude of minor details that we might not weary our readers, and we have kept aloof from disputed points that we might not get entangled 26 FROM THEORY TO FACT. in a purely scientific controversy. Our object has simply been to gather together into a systematic form those more general conclusions which, however startling they may seem to practical men of the world, and even to many of those whose minds have been accustomed to the pursuit of science in other departments, are never- theless regarded as certain by all who have devoted their lives to the study of Geology. It now remains to investigate the facts on which these conclusions are based, and to consider the line of argument by which so many able and earnest men have been led to accept them. In this vast field of inquiry we shall chiefly direct our attention to those points that bear upon the Antiquity of the Earth ; and in attempting to bring home to our readers the nature and the force of Geological reasoning, we shall confine ourselves altogether to simple and familiar illustrations. CHAPTER II. THEORY OF DENUDATION ILLUSTItATED BY FACTS. PRINCIPLE OP REASONING COMMON TO ALL THE PHYSICAL SCIENCES — THIS PRINCIPLE APPLICABLE TO GEOLOGY — OABBONIC ACID AN AGENT OP DENUDATION — VAST QUANTITY OP LIME DISSOLVED BY THE WATERS OF THE RHINE AND BORNE AWAY TO THE GERMAN OCEAN — DISINTEGRATION OP ROCKS BY PROST — PROFESSOR TYNDALL ON THE MATTERHORN — RUNNING WATER— ITS EROSIVE POWER — AN ACTIVE AND UNCEASING AGENT OF DENUDATION — MINERAL SEDIMENT CAR- RIED OUT TO SEA BY THE GANGES AND OTHER GREAT RIVERS — SOLID ROCKS UNDERMINED AND WORN AWAY — FALLS OF THE CLYDE AT LANARK — EXCAVATING POWER OF RIVERS IN AUVERGNE AND SICILY — FALLS OF NIAGARA — TRANSPORTING POWER OF RUNNING WATER — FLOODS IN SCOTLAND — INUNDATION IN THE VALLEY OP BAGNES IN SWITZERLAND. In the physical sciences it is a common principle of rea- soning to account for the phenomena that come before us in nature, by the operation of natural causes which we know to exist. Nay, this principle seems to be almost an instinct of our nature, which guides even the least philosophical amidst us, in the common affairs of life. When we stand amongst the ruins of an ancient castle, we feel quite certain that we have before us, not alone the monument of Time's destroying power, but also the monument of human skill and labour in days gone by. We entertain no doubt that ages ago the sound of the mason's hammer was heard upon these walls, now crowned with ivy ; that these moss-grown 28 REASONING OF GEOLOGISTS. Stones were once hewn fresh in the quarry, and piled up one upon another by human hands ; and that the building itself was designed by human skill, and in- tended for the purposes of human habitation and de- fence. Or, if we see a foot-print in the sand, we con- clude that a living foot has been there ; and from the character of the traces it has left, we judge what was the species of animal to which it belonged, whether man, or bird, or beast. It is true that God is Omnipotent. He might, if it had so pleased Him, have built the old castle at the creation of the world, and allowed it to crumble slowly into ruins : or He might have built it yesterday, and made a ruin begin to be where no castle had stood before ; and covered the stones with moss, and mantled the walls in ivy. And as to the footprint in the sand, it were as easy for Him to make the impress there, as to make the foot that left the impress. All this is true : but yet if any one were to argue in this style against us, he would fail to shake our convictions : we should still unhesitatingly believe that human hands once built the castle, and that a living foot once trod the shore. Now this principle of reasoning is the foundation on which the ablest modern Geologists claim to build their science. The untiring hand of Nature is ever busy around us : they ask us to come and look at her works, and to judge of what she has done in past ages, by that which she is now doing before our eyes. She is still, they say, building up her strata all over the globe, of limestone, and sandstone, and clay ; she is still lifting up in one place the bed of the ocean, and in another submerging REASONING OF GEOLOGISTS. 29 the dry land ; she is still bursting open the Crust of the Earth, by the action of internal fire, disturbing and tilt- ing up the horizontal strata ; she is still upheaving her mountains, and scooping out her valleys. All these operations are open to our inspection ; we may go forth and study them for ourselves ; we may examine the works that are wrought, and we may discover too the causes by which they are produced. And if it should appear that a very close analogy exists between these works that are now coming into existence, and the long series of works that are piled up in the Crust of the Earth, it is surely not unreasonable to refer the latter class of phenomena to the action of the same natural causes which we know to have produced the former. It cannot be denied that this argument is deserving of a fair and candid consideration. Let us proceed, then, to examine how far it is founded on fact, and how far it can be justly applied to the various heads of Geological theory. We will commence with the origin and history of Stratified Rocks ; for this constitutes, in a manner, the framework on which the whole system of Geology is supported and held together. It is alleged that the ele- ments of which Stratified Eocks are composed are but the broken fragments and minute atoms of pre-existing rocks, carried off" by the agents of Denudation, and spread out over some distant area in regular beds or layers; which, in progress of ages, were slowly consolidated into rocks of various quality and texture. With the view of testing this theory by the light of the principle just ex- plained we purpose, in the first place, to exhibit some 30 DECOMPOSITION OF GRANITE. examples of the many forms in which the process of De- nudation is going on at the present day all over the world ; and afterwards, to show that out of the materials thus obtained Stratified Eocks of every description — Mechanical, Chemical, Organic — are being regularly built up in sundry places ; and that these correspond in every essential feature with the Stratified Rocks in the Crust of the Earth. Among the chemical agents of Denudation, there is none more widely diffused than Carbonic acid gas. It is everywhere given out by dead animal and vegetable matter during the process of putrefaction ; it is plenti- fully evolved from springs in every country ; and it is emitted in enormous quantities from the earth in all volcanic districts, as well those in which the volcanos are now extinct as those in which they are active. Now it is well known from observation that carbonic acid has the property of decomposing many of the hardest rocks, especially those in which felspar is an ingredient. This phenomenon is exhibited on a large scale in the an- cient volcanic district of Auvergne in central France. The carbonic acid, which is abundantly evolved from the earth, penetrates the crevices and pores of the solid granite, . which being unable to resist its decomposing action, is rapidly crumbling to pieces. This mysterious decay of hard rock has been happily called by Dolomieu " la maladie du granite."' Again, all the water which flows over the surface of ' See Lyell's Principles of Geology, vol. i., pp. 41 1-413. LIMESTONE KOCK DISSOLVED. 3 i the land is highly charged with carbonic acid. The rain imbibes it in falling through the atmosphere ; and the rivers receive still further accessions from the earth as they pursue their course to the sea. In this combina- tion we discover a powerful agent of Denudation : for limestone rock wiU be dissolved by water which is im- pregnated with carbonic acid. Thus all the rivers and streams in the world, when they flow through a lime- stone channel, are constantly dissolving the solid rock and bearing away the elements of which it is composed. A single example will be sufficient to show the magni- tude of the results which are thus produced. It has been calculated by Bischof, a celebrated German che- mist, that the carbonate of lime which is carried each year to the sea by the waters of the Ehine, is sufficient for the formation of 32,000,000,000 of oyster shells : or, to view the matter in another light, it would be sufficient to produce a stratum of limestone one foot thick, and four square miles in extent.^ If such be the yearly produce of one river, how great must be the.accumulated effects of all the rivers in the world since our planet first came from the hand of its Creator. Passing from the chemical to the mechanical agents of Denudation, it is worth while to notice the immense power which is often generated by the agency of frost, especially in those countries that are subject to great vicissitudes of heat and cold. During a thaw, water finds its way into the clefts and joints by which all • See Jukes, The Student's Manual of Geology, p. 125. 32 FROST, AN AGENT OF DENUDATION. rocks are traversed, and when it is afterwards converted into ice, it expands with a mechanical force that is almost irresistible. The hardest rocks are burst asunder, great blocks are detached from the mountain side, and sent rolling down its slopes, or tumbling over crags and precipices, until at length they come to rest in shattered fragments at the bottom of the valley. In this condition they await but the coming of the winter's torrent to be borne still further on their long journey to the sea. The fearful havoc done in this way by the alternate action of sun and frost contributes in no small degree to the fantastic and picturesque forms assumed by the mountain peaks of Switzerland. Huge masses of rock have been literally hewn away until nothing has re- mained behind but those splintered obelisks and taper- ing pinnacles so familiar to the eye amidst the sublime scenery of the Alps. Indeed one of the greatest perils encountered by the adventurous spirits whose ambition it is to rival one another in the danger of their exploits, and to climb whatever was before regarded as inac- cessible, arises from the enormous fragments of rock which are rent almost unceasingly from the overhanging crags and hurled into the abysses below them. The fol- lowing incident related by Professor Tyndall is very much to the point. " We had gathered up our things, and bent to the work before us, when suddenly an ex- plosion occurred overhead. Looking aloft, in mid- air was seen a solid shot from the Matterhorn describing its proper parabola through the air. It split to pieces as it hit one of the rock-towers below, and its fragments PROFESSOR TYNDALL ON THE MATTERHORN. 33 came down in a kind of spray, which fell wide of us, but still near enough to compel a sharp look out. Two or three such explosions occurred afterwards, but we crept along the back fin of the mountain, from which the falling boulders were speedily deflected right and left." This occurred in 1862 on the occasion of an unsuc- cessful attempt to reach the highest peak of the Matter- horn. Six years later, when Professor Tyndall at length actually accomplished the object on which he seems to have set his heart, he found the work of destruction still going on. "We were now," he says in his narrative, "be- side a snow-gully, which was cut by a deep furrow along its centre, and otherwise scarred by the descent of stones. Here each man arranged his bundle and himself so as to cross the gully in the minimum of time. The pas- sage was safely made, a few flying shingle only coming down upon us. But danger declared itself where it was not expected. Joseph Maquignas led the way up the rocks. I was next, Pierre Maquignas next, and last of all the porters. Suddenly a yell issued from the leader : ' Cachez vous !' I crouched instinctively against the rock, which formed a by no means perfect shelter, when a boulder buzzed past me through the air, smote the rocks below me, and with a savage hum flew down to the lower glacier."' Even in our own country, every one is familiar with efficacy of the frozen water in producing landslips. The rain which soaks into the ground in winter, is converted into ice when frost sets in ; and upon steep slopes or ' Professor Tyndall, Odds and Ends of Alpine Life. D 34 MOVING WATEK, precipices, its expansive power bursts open the earth, and causes large masses of stones and clay to tumble headlong to the bottom. But moving water constitutes the most powerful, and, at the same time, the most universal agent of Denuda- tion. And it is chiefly to the effects of moving water that we mean to direct attention ; because its action is more striking to the eye, and more easily understood by the general reader. Every one is aware that the waters of the ocean are constantly passing off by evaporation into the higher regions of the atmosphere, and are there condensed into clouds. These clouds in course of time descend upon all parts of the earth, but especially on the high and mountainous districts. Then rivulets are formed which flow smoothly down the gentle slopes of the undulating country, or plunge headlong over the rocky mountain cliffs ; and the rivulets uniting form streams, and the streams, receiving new tributaries as they advance, become rivers ; and the rivers flow on to the sea, and discharge each day and each hour their enormous volumes of water back again into the ocean from which they came. Thus all the water of the world is constantly in motion, ever hurrying on, as it were, in one unending round of duty. This is the teaching of daily experience and observation. And we may add it is the teaching of Sacred Scripture as well. The Wise Man said long ago : " All the rivers run into the sea, yet the sea doth not overflow : unto the place from whence the rivers come, thither they return to flow again."' ' Eoolesiastes, i. 7. AN AGENT OF DENUDATION. 35 Now the power of this moving water is a mighty, wide-spread agent of change in the physical condition of the globe. For wherever water is in motion over the surface of the land, whether it be a rippling stream, or a mountain torrent, or a majestic river, it is surely wearing away the channel through which it flows, and carrying along in its course particles of clay, or sand, or gravel. This subject is illustrated with great force and great simplicity by Mr. Page. " Every person," he says, " must have observed the rivers in his own district, how they become muddy and turbid during floods of rain, and how their swollen currents eat away the banks, deepen the channels, and sweep away the sand and gravel down to some lower level. And if, during this turbid state, he will have the curiosity to lift a gallon of the water, and allow it to settle, he will be astonished at the amount of sediment or solid matter that falls to the bottom. Now, let him multiply this gallon by the number of gallons daily carried down by the river, and this day by years and centuries, and he will arrive at some faint idea of the quantity of matter worn from the land by rivers, and deposited by them in the ocean. In the same way as one river grinds and cuts for itself a chan- nel, so does every stream and rill and current of water. The rain as it falls washes away what the winds and frosts have loosened ; the rill takes it up, and, mingling it with its own burden, gives it to the stream ; the stream takes it up and carries it to the river ; and the river bears it to the ocean."' • Page, Advanced Text Book of Geology, p. 55. D 2 36 SOLID MATTER CAEEIED OUT TO SEA. When the current is feeble, the greater part of this earthy material is thrown down upon the way, and forms a stratum of alluvial soil in the bed of the river, and also in the adjoining lowlands during the time of temporary floods. But when several streams unite, then the carrying power of the current is enormously in- creased : huge stones are roUed along, and dashed one against another, and broken into fragments, and the fragments are rounded by friction, and become pebbles, and the pebbles become gravel, and the gravel, mud ; and the mud is carried on to the mouth of the river, and there falling to the bottom, it forms a tongue of land which is called a delta ; or else perhaps it chances to meet with some great ocean current, and then it begins a new journey, and is borne far away to be deposited in the profound and tranquil depths of the sea. It is not, however, mineral matter alone that is transported by the action of rivers. Trees that once were growing on the banks of the stream, and the bones of animals, and human remains, and works of art, are seen floating down with the current, and are found imbedded in the sand and mud of the delta at the river's mouth. These are some of the actual realities which all may witness, who will go and study for themselves the history of this wonderful element, from the time when it first soars aloft as vapour to the sky, until it returns to the bosom of its parent ocean laden with the spoils of the land. To some of our readers, perhaps, results of this kind may appear insignificant, when considered in re- lation to the enormous bulk of the stratified rocks. But THE RIVER GANGES. 37 it should be remembered that the force of which we speak is unceasing in its operation over the whole sur- face of the earth ; and even though the work were small which is accomplished in each successive year, the ac- cumulated effects produced in a lengthened period of time must be immensely great. Besides, it would be a very serious error to form our ideas on this subject, as many would seem to do, from the examples which are to be found within the narrow limits of our own island. We should rather seek for our illustrations among those mighty rivers that drain the vast continents of the world, and exhibit the erosive and transporting power of run- ning water on the grandest scale. It happens, fortunately for our purpose, that an at- tempt has been made by scientific men, to compute the amount of matter discharged into the sea, by some par- ticular rivers within a given time. For such a compu- tation it is necessary, in the first place, to calculate the volume of water that passes down the channel during that time ; and then by repeated experiments, to ascer- tain the average proportion of earthy matter which is held suspended in the water. This has been done with the greatest care by the Rev. Mr. Everest, in the case of the river Ganges ; and it appears that during the rainy season, which lasts four months every year, from June to September, about 6,000,000,000 cubic feet of mud are carried along by the stream past the town of Ghaze- poor, near which the observations were made. Now this enormous bulk of mineral matter would be sufficient to form a Stratum of rock one foot in height, and two 38 THE MISSISSIPPI. hundred and eighteen square miles in extent. Or, to adopt the computation of Sir Charles Lyell, the amount which passes by every day is equal to that which might be transported by 2000 Indiamen, each freighted with a cargo of mud 1400 tons in weight. And it is im- portant to remember that this estimate represents but a portion of the sediment which passes into the sea through the channel of the Ganges ; for the observations of Mr. Everest were taken at a point which is 500 miles from the sea, and at which the river has not yet re- ceived the contributions of its largest tributaries. We are able, therefore, with some degree of confidence to estimate the amount of Denudation which is every year effected by the Ganges. And, although the same calculations have not yet been applied with equal care to other great rivers, there is no reason to suppose that the Ganges is an exception. It is asserted on good grounds that the Brahmapootra, which unites with the Gano-es close to the Bay of Bengal, carries with it an equal amount of earthy sediment. According to Sir Charles Lyell, the quantity of solid matter brought down each year by the Mississippi amounts to 3,702,758,400 cubic feet. And it is said that 48,000,000 cubic feet of earth are daily discharged into the sea by the Yellow Eiver in China, called by the natives the Hoang Ho.' Thus year after year the waste of the land is carried away by rivers, ' See on this subject, LyeU's Principles of Geology, vol. i. p. 458, and pp. 480-3; Jutes, Manual of Geology, pp. ,05-ri; Page, Advanced Text Book of Geology, pp. 52-56. MASSIVE ROCKS UNDERMINED. 39 to be spread out over wide areas of the ocean and per- haps to furnish the materials of future continents. The effects of running water in wearing away and transporting masses of solid rock are not less deserving of our notice. Every one who has followed the course of a great river when it flows through a rocky channel, must have observed large blocks projecting from the cliffs above, which, having been undermined by the action of the water, seem ready to tumble headlong into the stream ; and others lying below, which had fallen before ; and others again which had been already car- ried a considerable distance by the winter's torrent. Even where the rocks are not displaced, they are gra- dually being worn away, partly by the friction of the water, but much more by the grinding action of the gravel which the water holds in suspension. Not only is the surface of the rocks thus rounded and polished, but large circular pits, called pot-Koles, are formed by the whirling waters of an eddy carrying round and round a few grains of hard sand. At the falls of the Clyde near Lanark in Scotland, these various phenomena may be seen to great advan- tage. Good illustrations are to be found also in many volcanic regions. Some of the larger streams in Au- vergne have in course of time forced their way through the solid lava rock, cutting out for themselves channels broad and deep. In Sicily too, we are told, the river Simeto, whose course was blocked up by a current of lava about the beginning of the seventeenth century, has since that time eaten its way through this compact 40 THE FALLS OF NIAGARA. and hardened mass, and now flows on to the sea through a rocky passage forty feet in depth and from fifty to several hundred feet in width.' But there is no part of the world yet explored where these effects are exhibited on the same gigantic scale as at the far famed Falls of Niagara. The massive lime- stone rock from which the waters are precipitated is slowly but certainly disappearing. An enormous vo- lume of water, more than a third of a mile in breadth, plunges in a single bound over a sheer precipice of one hundred and sixty-five feet. The soft slaty rocks upon which the limestone rests are soon eaten away by the action of the spray which rises from the pool below ; and then the overhanging cliffs, left without any support, topple over, and are carried off by the torrent. The position of the Falls, therefore, is not stationary, but is receding by very sensible degrees in the direction of Lake Erie, from which the river flows. Speaking of this phenomenon Sir Charles Lyell observes with much show of reason : " The idea of perpetual and progressive waste is constantly present to the mind of every be- holder ; and as that part of the chasm which has been the work of the last hundred and fifty years resembles precisely in depth, width, and character, the rest of the gorge, which extends seven miles below, it is most na- tural to infer, that the entire ravine has been hollowed out in the same manner, by the recession of the cataract. It must at least be conceded, that the river supplies an ' Lyell, Principles of Geology, vol. i. pp. 356-7. ROCKS -TRANSPORTED BY RUNNING WATER. 41 adequate cause for executing the whole task thus as- signed to it, provided we grant sufficient time for its completion."' With a view to enable our readers to understand more fully the prodigious force which rivers have been known to exert in the transportation of rocks, it may be useful to draw attention to one or two principles of physical science. First, we have the well known law of Archi- medes, that a solid body immersed in a liquid loses a part of its weight equal to the weight of the liquid displaced. Now solid rock as compared with water, bulk for bulk, is rarely more than three times, and often not more than twice as heavy. Consequently, according to this law, almost all rocks will lose a third of their weight, and many will lose one-half, when immersed in water. Again, it has been established that the power of water to move bodies that are in it increases as the sixth power of the ve- locity of the ciirrent. Hence, if the velocity of a current is increased two-fold, its moving power will be increased sixty-four fold ; if the velocity is increased three-fold, the moving power will be increased seven hundred and twenty fold; and so on. From these principles it follows, first, that a much smaller power is required to move a block of stone lying in the bed of a riv6r, than if it were lying on the surface of the land ; and secondly, that a very slight increase in the velocity of a current efiects a very great increase in its moving power. We need not wonder, then, when 1 Piinoiples of Geology, vol. i. p. 360. 42 ILLUSTRATIONS. we hear of the enormous masses of rocks and trees and masonwork which are carried away even by small rivers in times of flood.' Here are a few examples. In August, 1829, a frag- ment of sandstone, fourteen feet long, three feet wide, and one foot thick, was carried by the river Nairn, in Scotland, a distance of two hundred yards. On the same occasion the river Dee swept away a bridge of five arches, built of solid granite, which had stood uninjured for twenty years ; the whole mass of masonry sunk into the bed of the stream and was seen no more. And the river Don, as we are assured on the authority of Mr. Far- quharson, forced a mass of stones four or five hundred tons in weight up a steep inclined plane, leaving them in a great rectangular heap on the summit. A small rivulet called the College, in Northumberland, when swollen by a flood in August, 1827, "tore away from the abutment of a mill-dam a large block of greenstone- porphyry weighing nearly two tons, and transported it to the distance of a quarter of a mile."' But it is need- less to multiply examples of phenomena which are oc- curring every day around us and of which many among our readers have probably been eye-witnesses. The transporting power of rivers must not always be estimated by the bulk and velocity -of the current ; for ' See Jukes, Manual of Geology, pp. 108-10 ; Hopkins, Presidential Address to the Geological Society of London, 1852, p. xxvii. 2 For these facts see Lyell, Principles of Geology, vol. i., pp. 349, 350 ; Quarterly Journal of Science, No. xiii., New Series ; The English Cy- clopEedia, Natural History Division, Alluvium. FLOOD IN THE VALLEY OF BAGNES. 43 it is often greatly increased by some accidental obstruc- tion, which for a time blocks up the channel through which the river flows. An instructive illustration is afforded by the river Dranse, which flows through the valley of Bagnes, in Switzerland, and empties itself into the Rhone above the lake of Geneva. In the year 1 8 1 8 the avalanches which fell down from the mountain side formed a barrier across the valley, and thus effectually blocked up the course of the stream. The upper part of the valley was, in consequence, soon converted into a lake which gradually increased in size as the season ad- vanced. When summer came, and the melting of the snows began, the ice barrier suddenly gave way with a tremendous crash, and the lake was emptied in half an hour. The mass of water, thus in a moment disengaged, burst with destructive violence over the lower valley, sweeping away rocks, forests, houses, bridges, and cul- tivated lands. Thousands of trees were torn up by the roots, fragments of granite as large as houses were rolled along, and the whole flood presented the appearance of a moving mass of ruins. CHAPTER III. THEORY OF DENUDATION — FURTHER ILLUSTRATIONS. THE BREAKERS OE THE OCEAN — CAVERNS AND PAIKT ER:DGES OP KILKEE — ITALY AND SICILY — THE SHETLAND ISLANDS — EAST AND SOUTH COAST OF BRITAIN — TRACTS OP LAND SWALLOWED UP BY THE SEA — ISLAND OP HELI80LAND — NORTHSTRAND — TIDES AND CUR- RENTS — SOUTH ATLANTIC CURRENT — EQUATORIAL CURRENT — THE GULP STREAM — ITS COURSE DESCRIBED — EXAMPLES OP ITS POWER AS AN AGENT OP TRANSPORT. While the rain, the rivers, and the streams, are thus wasting away the mountains and plains of the interior country, the waves of the sea are exerting a power no less destructive on the coasts of islands and of continents. The breakers dashing against the foot of a lofty cliff, dissolve and decompose and wear away the lower strata ; and the overhanging rocks, thus undermined, fall down in course of time by their own weight. With the next returning wave these rocks are themselves hurled back against the cliff; and so, as some one has happily remarked, the land would seem to supply a powerful artillery for its own destruction. The effects of the breakers are often very unequal, even on the same line of cliffs. Some parts of the rock are more yielding than others, or perhaps they are more exposed to the action of the waves, or perhaps they are divided by larger joints and more freely admit the destructive element. These parts will be the first to give way, while the FAIRY BRIDGES OF KILKEE. 45 harder and less exposed rock will be left standing : and in this way forms the most capricious and fantastic are produced. No finer examples could be wished for than those which are seen in the neighbourhood of Kilkee, and along the promontory of Loop Head, in the county of Clare. Sometimes the ground is undermined with ca- verns, into which, when the tide is coming in, the waves of the Atlantic rush with resistless force, making new additions each day to the accumulated ruins of ages. Sometimes lofty pinnacles of rock are left standing in the midst of the waters, like giant sentinels stationed there by Nature to guard the coast. In one or two in- stances these isolated fragments are connected with the main land by natural arches of rock which are called fairy bridges by the people : but more commonly they appear as rocky islets, and answer exactly to the poet's description — " The roaring tides The passage broke that land from land divides ; And where the lands retired the rushing ocean rides." It is interesting to observe in passing, that, in the original verses of the ^neid, of which these lines are Dryden's translation, Virgil has recorded a belief which prevailed in his time, and which, upon scientific grounds, is now regarded as highly probable by Geologists, that the island of Sicily had been once connected by land with Italy, and was separated from it by the action of the waves : " Haeo loca, vi quondam et vasta convulsa ruina, Tantum aevi longinqua valet mutare vetustas ! 46 THE SHETLAND ISLANDS. Dissiluisse ferunt, quum protenus utraque tellus Una foret ; venit medio yi pontus et undis Hesperium Siculo latus atacidit, arvaque et urbes Litore deduotas angusto interluit aestu." ^neid, iii. 414-19. But whatever may be thought of this opinion thus rendered immortal by the genius of the poet, we shall not stop to discuss Its merits. For in the present stage of our argument, it is our object to deal not with vague and uncertain traditions, nor even with philosophical speculations, but rather with the facts which are actually going on in nature, and which any one of our readers may examine for himself. With this object in view, we shall take a few examples from the Eastern and Southern coasts of Great Britain, which have been carefully ex- plored by scientific men for the purpose of observing and recording the amount of destruction accomplished by the waves within recent times. The Shetland Islands, exposed to the whole fury of the Atlantic, present many phenomena not unlike those of Kilkee and Loop Head, but upon a far grander scale. Whole islands have been swept away by the resistless power of the waters, and of others nothing remains but massive pillars of hard rock, which have been well de- scribed as rising up " like the ruins of Palmyra in the desert of the ocean."* Passing to the mainland, it is re- corded that in the year 1795 a village in Kincardine- shire was carried away in a single night, and the sea advanced a hundred and fifty yards inland, where it has ever since maintained its ground. In England almost ENCROACHMENTS OF THE SEA. 47 the whole coast of Yorkshire is undergoing constant di- lapidation. On the south side of Flamborough Head Fig. I. Granitic rocks to the south of Hillswick Ness, Shetland. From Lyell's Principles of Geology. the cliffs are receding at an average rate of two yards and a quarter in the year, for a distance of thirty-six miles along the coast. This would amount to a mile since the Norman Conquest, and to more than two miles since the occupation of York by the Komans. It is not surprising, therefore, to learn that many spots marked in the old maps of the country as the sites of towns or villages, are now sandbanks in the sea. Even places of historic name have not been spared. The town of Kaven- spur, from which, in 1332, Edward Baliol sailed for the invasion of Scotland, and at which Henry the Fourth landed in 1399, to claim the throne of England, has long since been swallowed up by the devouring element. ENCROACHMENTS OF THE SEA. On the coast of Norfolk it was calculated, at the be- ginning of the present century, that the mean loss of the land was something less than one yard in the year. The inn at Sherringham was built on this calculation in 1 80 J, and it was expected to stand for seventy years. But unfortunately the actual advance of the sea exceeded the calculation. Sir Charles Lyell, who visited this spot in 1829, relates that during the five preceding years seventeen yards of the cliff had been swept away, and nothing but a small garden was then left between the building and the sea. The same distinguished writer tells us that in the harbour of this town there was at that time water sufficient to float a frigate where forty-eight years before had stood a cliff fifty feet in height with houses built upon it. And remarking upon these facts, he says, that "if once in half a century an equal amount of change were produced suddenly by the momentary shock of an earthquake, history would be filled with records of such wonderful revolutions of the earth's sur- face ; but if the conversion of high land into deep sea be gradual, it excites only local attention." In the neighbourhood of Dunwich, once the most con- siderable seaport on the coast of Suffolk, the cliffs have been wasting away from an early period of history. "Two tracts of land which had been taxed in the time of King Edward the Confessor, are mentioned in the Conqueror's survey, made but a few years afterwards, as having been devoured by the sea." And the memory of other losses in the town itself— including a monastery, several churches, the town-hall, the gaol, and many ENCROACHMENTS OF THE SEA. 49 hundred houses — together with the dates of their occur- rence, is faithfully preserved in authentic records. In 1 740 the sea reached the churchyard of Saint Nicholas and Saint Francis, so that the graves, the coffins, and the skeletons, were exposed to view on the face of the cliffs. Since that time the coffins, and the tombstones, and the churchyard itself, have disappeared beneath the waves. Nothing now remains of this once flourishing and populous city but the name alone, which is still at- tached to a little village of about twenty houses. The spot on which the Church of Reculver stands, near the mouth of the Thames, was a mile inland in the reign of Henry the Eighth; in the year 1834 it was overhanging the sea ; and it would long ago have been demolished, but for an artificial causeway of stones constructed with a view to break the force of the waves. It is estimated that the land on the north-east coast of Kent is receding at the rate of about two feet in the year. The promon- tory of Beachy Head in Sussex is also rapidly falling away. In the year 1 8 1 3 an enormous mass of chalk, three hundred feet in length and eighty in breadth, came down with a tremendous crash ; and slips of the same kind have often occurred, both before and since. To these examples from Great Britain we may add one or two from the German Ocean. Seven islands have completely disappeared within a very narrow area since the time of Pliny ; for he counted twenty -three between Texel and the mouth of the Eider, whereas now there are but sixteen. The island of Heligoland, at the mouth of the Elbe, has been for ages subject to great dilapida- E 50 ENCROACHMENTS OP THE SEA. tion. Within the last five hundred years three-fourths of it have been carried away; and since 1770 the frag- ment that remains has been divided into two parts by a channel which is at present navigable for large ships. A still more remarkable instance of destruction effected by the waves of the sea occurred in the island of North- strand, on the coast of Schleswig. Previous to the thirteenth century it was attached to the mainland, forming a part of the continent of Europe, and was a highly cultivated and populous district about ten miles long, and from six to eight broad. In the year 124Q it was cut off from the coast of Schleswig by an inroad of the sea, and it gradually wasted away up to the seven- teenth century, when its entire circumference was six- teen geographical miles. Even then the industrious inhabitants, — about nine thousand in number, — endea- voured to save what remained of their territory by the erection of lofty dykes ; but on the eleventh of October, 1634, the whole island was overwhelmed by another in- vasion of the sea in which 6000 people perished, and 50,000 head of cattle. Three small islets are all that now remain of this once fertile district.' The breakers of the ocean receive no small aid in their work of destruction from the action of tides and currents ' For these facts illustrating the destructive action of tie waves of the sea we are chiefly indebted to the following authorities : Hihbert, De- scription of the Shetland Isles; Phillips, Rivers, Mountains, and Sea- coast of Yorkshire ; Geology of Yorkshire, by the same author ; Pennant's Arctic Zoology, vol. i. ; Lyell's Principles of Geology, vol. i. chapters xx.andxxi.; Gardner's History of the borough of Dun wich; the English Cyclopffidia, AUuvium. TIDES AND CUEUEN'IS. J I which co-operate with the winds to keep the waters of the sea in constant motion. And though the winds may sleep for a time, the tides and currents are always actively at work, and never for a moment cease to wear away the land. But they are even more powerful auxiliaries as agents of transport. If it were not for them, the ruins which fall from the rocks -to-day would to-morrow form a barrier against the waves, and the work of destruction would cease. But Nature has or- dained it otherwise. When the tide advances it rolls the broken fragments towards the land, and when it recedes, it carries them back to the deep ; and so by unceasing friction these fragments are worn away to pebbles, and then, being more easily transported, they are carried off to sea and deposited in the bed of the ocean : or else, perhaps, they are cast up on the sloping shore to form what is so familiar to us all under the name of a shingle beach. This is a subject on which it is needless to enlarge. Every one knows that the tides have the power of trans- porting solid matter ; though most of us, perhaps, do not fully appreciate the magnitude of their accumulated effects, working as they do with untiring energies upon the coasts of islands and continents all over the world. It is not, however, so generally known that the ocean is traversed in all directions by powerful currents, which, from their regularity, their permanence, and their ex- tent, have been aptly called the rivers of the ocean. We do not mean hereto inquire into the causes of these currents, upon which the progress of physical science has E 2 52 THE GULF-STREAM. thrown considerable light : neither can we hope to de- scribe even the principal currents that prevail over the vast tracts of water which constitute about three-fourths of the entire surface of our globe. We shall content ourselves with tracing the course of one great system, which may serve to give some idea of their general character and enormous power. This system would seem to have its origin with a stream that flows from the Indian Ocean towards the south-west, and then doubling the Cape of Good Hope, turns northward along the African coast. It is here called the South Atlantic Current. When it encounters the shores of Guinea, it is diverted to the west, and stretches across the Atlantic, traversing forty degrees of longitude until it reaches the projecting promontory of Brazil in South America. In this part of its course it is known as the Equatorial Current, because it follows pretty nearly the line of the Equator : it varies in breadth from two hundred to five hundred miles, and it travels at the mean rate of thirty miles a day, though sometimes its velocity is increased to seventy or eighty. Next, under the name of the Guyana Current, it pursues a north- westerly direction, following the line of the coast ; and passing close to the island of Trinidad, becomes dif- fused, and almost seems to be lost, in the Caribbean Sea. Nevertheless it again issues with renewed energy from the Gulf of Mexico, and rushing through the Straits of Florida at the rate of four and five miles an hour, it issues once more into the broad waters of the Atlantic. From this out it is called the Gulf-stream, and is well THE GULF-STREAM. S3 known to all who are concerned in Transatlantic navi- gation ; for it sensibly accelerates the speed of vessels which are bound from America to Europe, and sensibly retards those sailing from Europe to America. The Gulf-stream, however, does not set out on its Transatlantic voyage directly that it issues from the Straits of Florida. It keeps at first a north-easterly course, following the outline of the American continent, passing by New York and Nova Scotia, and brushing the southern extremity of the great Newfoundland Bank. Then taking leave of the land it sweeps right across the Atlantic. After a time it seems to divide into two branches, one inclining to the south, and losing itself among the Azores, the other bending towards the north, washing the shores of Ireland, Scotland, Norway, and reaching even to the frozen regions of Spitzbergen. The breadth of the Gulf-stream when it issues from the Straits of Florida is about fifty miles, but it afterwards increases to three hundred. Its colour is a dark indigo blue, which, contrasting sharply with the green waters of the Atlantic, forms a line of junction distinctly visible for some hundreds of miles: afterwards, when this boundary line is no longer sensible to the eye, it is easily ascertained by the thermometer, for the tempera- ture of the Gulf-Stream is everywhere from eight to ten degrees higher than that of the surrounding ocean.' 1 Rennell's Investigation of the Currents in tlie Atlantic Ocean ; Maury's Physical Geography of the Sea, Chapters ii. and iii. ; Humboldt's Cosmos; The English Cyclopaedia, Atlantic Ocean; Lyell's Principles of Geology, vol. i. chapter xx. 54 GEOLOGICAL IMPOETANCE We leave our readers to infer from this brief descrip- tion how immense must be the power of transport which belongs to such currents as these. They sweep along the shores of continents, and carry away the accumu- lated fragments of rock, which had first been rent from the cliffs by the waves of the sea, and then borne out to a little distance by the tides : they pass by the mouths of great rivers, and receiving the spoils of many a fer- tile and populous country, and the ruins of many an in- accessible mountain ridge, they hurry off to deposit this vast and varied freight in the deep abysses of the ocean. There is one circumstance, however, which we ought not to pass over in silence ; for it is of especial impor- tance to the Geologist, and might easily escape the notice of the general reader. It is a well ascertained fact that plants and fruits and other objects from the West Indian Islands are annually washed ashore by the Gulf-stream on the north-western coasts of Europe. The mast of a man-of-war burnt at Jamaica was after some months found stranded on one of the Western Islands of Scot- land ;i and General Sabine tells us that when he was in Norway in the year 1823, casks of palm oil were picked up on the shore near the North Cape, which belonged to a vessel that had been wrecked the previous year at Cape Lopez on the African coast." It seems most pro- bable that these casks of oil must first have crossed the Atlantic from east- to west in the Equatorial Current, 1 Mantell's Wonders of Geology, p. 70. ' In his notes to the translation of Humboldt's Cosmos, p. xcvii. OF OCEAN CUERENTS. 55 then described the circuit of the West Indian Islands, and finally coming in with the Gulf- stream, recrossed the Atlantic, performing altogether a journey of more than eight thousand miles. From these facts it is clear that, by the agency of ocean currents, the productions of one country may be carried to another that is far distant. And Geologists do not fail to make use of this important conclusion when they find the animal and vegetable remains of different climates associated toge- ther in the same strata of the Earth. CHAPTER IV. THEORY OF DENUDATION — CONCLUDED. GIACIEKS THEIB NATURE AND COMPOSITION — THEIR VNCEABINO MOTION — POWEEPUL AGENTS OP DENUDATION — ICEBEEGS THEtll NUMEEE AND SIZE — EEEATIC BLOCKS AND LOOSE GEAVEL BPKBAD OUT OVER MOUNTAINS, PLAINS, AND VALLEYS, AT THE BOTTOM OP THE SEA — CHARACTERISTIC MARKS OP MOVING ICE — EVIDENCE OF ANCIENT GLACIAL ACTION — ILLUSTEATIONS PROM THE ALPS — PEOM THE MOUNTAINS OP THE JUEA — THEOEY APPLIED TO NOETHERN EUROPE — TO SCOTLAND, WALES, AND IRELAND — THE PACT OP DENU- DATION ESTABLISHED — SUMMARY OP THE EVIDENCE — THIS PACT THE FIRST STEP IN GEOLOGICAL THEOEY. The next agent of Denudation to which we invite the attention of our readers, is one of which our own coun- try affords us no example, but which may be seen in full operation amidst the wild and impressive scenery of Switzerland. And we know not how we can better intro- duce the subject than by the solemn address of a great poet, in whom an ardent love of nature was blended with a deep sense of religion. As he stood in the midst of the snow-clad mountains that shut in the valley of Chamouni, his spirit, " expanded by the genius of the spot," soared away from the scenes before him to the Great Invisible Author of all that is beautiful and sublime in nature, and he poured forth that well-known hymn of praise and worship in which he thus apostrophizes the massive Glaciers of Mont Blanc : — " Te icc-falla ! ye that from the mountain's hrow Adown enormous ravines slope amain — THE GLACIER. S7 Torrents, methinks, that heard a mighty voice, And stopped at onco amid their maddest plunge ! Motionless torrents ! silent cataracts ! Who made you glorious as the gates of Heaven Beneath the keen full moon ? Who bade the sun Clothe you with rainbows ? Who with living flowers Of loveliest blue, spread garlands at your feet ? God ! let the torrents, like a shout of nations, Answer ! and let the ice-plains echo, God ! God ! sing ye meadow-streams with gladsome voice ! Ye pine groves, with your soft and soul-like sounds ! And they too have a voice, yon piles of snow, And in their perUons fall shall thunder, God !"' A Glacier is an enormous mass of solid ice filling up a valley, and stretching from the eternal snows which crown the summits of the mountains, down to the smiling corn fields and rich pastures of the plains. It is con- stantly fed by the accumulated snows of winter, which, slipping and rolling down the slopes of the mountains, lodge in the valleys below, and are there converted into ice. For it must be remembered that the Glacier pro- perly so called does not commonly extend much higher than 9000 feet aboVe the level of the sea. Beyond that elevation the compact and massive ice gradually passes into frozen snow, called by the French Nev^, and by the Germans Firn. The change which takes place in the condition of the snow as it descends into the valley is chiefly owing to these two circumstances ; first, it is closely compacted together by the weight of the snowy masses pressing down upon it from above ; and secondly, in the summer months it is thawed upon the surface 1 A Hymn before Sunrise in the Vale of Chamouni, by Samuel Tay- lor Coleridge. 58 " THK glacier's COLD AND RESTLESS MASS during the day by the heat of the sun, and frozen again at night. On a small scale this process is practically familiar to every school-boy. When he makes a snow- ball he is practically converting a mass of snow into ice, and that by a series of operations very closely resem- bling those which Nature employs in the manufacture of a Glacier. In Switzerland the Glacier is often two or three miles in breadth, from twenty to thirty miles in length, and five or six hundred feet in depth. Though so vast in its bulk and so solid in its character, it is not, as might be supposed, a fixed, immovable mass. On the con- trary, it is moving incessantly, but slowly, down the valley which it occupies, at the rate of several inches — sometimes one or two feet, and even more — in the day. In Greenland a Glacier explored by Doctor Hayes, in his expedition to the North Pole, was found to move for a whole year at the average rate of a hundred feet a day. It may be thought, perhaps, that this fact requires further confirmation : but at all events it is certain that the language of the poet, when he ad&resses the Glaciers as " motionless torrents," though it conveys an accurate and beautiful idea of the appearance they present to the eye, is not rigorously true in a scientific sense. Indeed, it is just because the Glaciers are not motionless that they serve as instruments of Denudation. Their agency in this respect " consists partly in their power of transporting gravel, sand, and huge stones, to great distances, and partly in the smoothing, polishing, and scoring of their rocky channels, and the boundary MOVES ONWARD DAY BY DAY. 59 walls of the valleys through which they pass. At the foot of every steep cliff or precipice in high Alpine re- gions, a sloping heap is seen of rocky fragments detached by the alternate action of frost and thaw. If these loose masses, instead of accumulating on a stationary base, happen to fall upon a Glacier, they will move along with it, and, in place of a single heap, they will form in the course of years a long stream of blocks. If a Glacier be twenty miles long, and its annual progression about five hundred feet, it will require about two centuries for a block thus lodged upon its surface to travel down from the higher to the lower regions, or to the extremity of the icy mass. This terminal point usually remains un- changed from year to year, although every part of the ice is in motion, because the liquefaction by heat is just sufficient to balance the onward movement of the Gla- cier, which may be compared to an endless file of sol- diers, pouring into a breach, and shot down as fast as they advance. " The stones carried along on the ice are called in Switzerland the moraines of the Glacier. There is al- ways one line of blocks on each side or edge of the icy stream, and often several in the middle, where they are arranged in long ridges or mounds of snow and ice, often several yards high. The reason of their project- ing above the general level, is the non-liquefaction of the ice in those parts of the surface of the Glacier which are protected from the rays of the sun, or the action of the wind, by the covering of the earth, sand, and stones. The cause of medial moraines was first explained by 6o VALLEYS SCOOPED GOT BY GLACIERS. Agassiz, who referred them to the confluence of tribu- tary Glaciers. Upon the union of two streams of ice, the right lateral moraine of one of the streams comes in contact with the left lateral moraine of the other, and they afterwards move on together, in the centre, if the confluent Glaciers are equal in size, or nearer to one side if unequal. " Fragments of stone and sand which fall through ere- vasses m the ice, and get interposed between the moving Glacier and the fundamental rock, are pushed along so as to have their angles more or less worn off, and many of them are entirely ground down into mud. Some blocks are pushed along between the ice and the steep boundary rocks of the valley, and these, like the rocky channel at the bottom of the valley, often become smoothed and polished, and scored with parallel furrows, or with lines and scratches produced by hard minerals, such as crystals of quartz, which act like the diamond upon glass. The effect is perfectly different from that caused by the ac- tion of water, or a muddy torrent forcing along heavy stones ; for these not being held like fragments of rock in ice, and not being pushed along under great pressure, cannot scoop out long rectilinear furrows or grooves parallel to each other. The discovery of such markings at various heights far above the surface of existing Glaciers, and for miles beyond their present termina- tions, affords geological evidence ofthe former extension ot the ice beyond its present limits in Switzerland and other countries."' ' LyeU's Principles of Geology, vol. i. pp. 374-3, ICEBERGS. 6l Sometimes, however, it happens, especially in extreme northern and southern latitudes, that the glacier valley leads down to the sea. In such cases, huge masses of ice are floated off, and, with their ponderous burden of gravel, mud, and rocks, are carried away by currents towards the equator. Immense numbers of these floating islands of ice, or Icebergs, as they are called, are seen by mariners drifting along in the Northern and Southern oceans. In 1822 Scoresby counted five hundred be- tween the latitudes 69° and 70° N., many of which mea- Fig. 2. Iceberg seen in mid ocean 1400 miles from any known land. sured a mile in circumference, and rose two hundred feet above the surface of the sea.' The annexed draw- ing, copied by kind permission of the author from Sir 1 Voyage in 1822, p. 233. 62 TRANSPORTING POWER OF ICEBERGS. Charles Lyell's Principles of Geology, affords a good idea of the appearance that such Icebergs present to the eye. The one represented in the foreground was supposed to reaqji a height of nearly three hundred feet, and was observed with many others floating about in the Southern Ocean at a distance of 1400 miles from any known land. An angular mass of rock was visible on the surface. The part exposed was twelve feet high and from five to six broad : but it was conjectured, from the colour of the surrounding ice, that the greater part of the stone was concealed from view. How enormous must be the magnitude of those pon- derous masses may be learned from the fact that the bulk of ice below the level of the water is about eight times as great as that above : and in point of fact, Captain Sir John Ross saw several of them aground in Baffin's Bay, where the water was 1500 feet deep. It has been calculated that the beds of earth and stones which they carry along cannot be less than from 50,000 to 100,000 tons in weight. Sir Charles Lyell, writing in 1865 from the results of the latest investigations on this subject, says : " Many had supposed that the magnitude commonly attributed to icebergs by un- scientific navigators was exaggerated ; but now it ap- pears 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 two to five miles in length. Captain d'Urville ascertained one of ANCIENT GLACIAL PERIOD. 63 them, which he saw floating, to be thirteen miles long, and a hundred feet high, with walls perfectly vertical."' They have been known to drift from Baffin's Bay to the Azores, and from the South Pole to the Cape of Good Hope.' As they approach the milder climate of the temperate zones, the ice gradually melts away, and thus the moraines of arctic and antarctic glaciers are de- posited at the bottom of the deep sea. In this way, sub- marine mountains and valleys and table lands, are strewn over with scattered blocks of foreign rocks, and gravel, and mud, which have been transported hundreds of miles across the unfathomable abysses of the ocean. Though we are chiefly concerned with Glaciers and Icebergs as agents of Denudation, yet we cannot pass away from the subject without referring to the Geolo- gical theory of an ancient Glacial Period. This little digression from the main purport of our present argu- ment will not be unacceptable, we hope, to our readers. The theory is in itself interest'ing and ingenious ; and it offers an admirable illustration of the kind of reasoning by which Geologists ate guided in their speculations. It is well known that the action of moving ice leaves a very peculiar and characteristic impress on the surface of the rocks, and even on the general aspect of the country, over which it passes. This is no mystei-y of science but a plain fact which any one that chooses may observe for himself. Every Glacier carries along 1 Elements of Geology, pp. 145, 146- 2 Captain Horsburg, On Icebergs in Lo-vr Latitudes. Phil. Trans. 1830. 64 CHARACTERISTIC MARKS in its course a vast quantity of loose gravel, hard sand, and large angular stones. A considerable proportion of these materials in course of time fall through crevasses in the ice, and become firmly imbedded in the under surface of the Glacier. Then, as the moving mass slowly descends the valley, they are shoved along under enor- mous pressure, and the surface of the rocks beneath is Fig- 3- Block of Limestone furrowed, scratched, and polished, from the Glacier of Rosenlaui, Switzerland. (Lyell.) aa. White streaks or scratches, hi. Furrows. furrowed, scratched, and polished, in a remarkable and unmistakable manner. The furrows and scratches are rectilinear and parallel to an extent never seen in the OF MOVING ICE. 65 marks produced by any other natural agency : and they always coincide more or less in their direction with the general course of the valley. A reciprocal action often takes place : the large blocks of stone, frozen into the under surface of the Glacier, are themselves scored and polished by friction against the floor and sides of the valley. Similar effects are produced by Icebergs; not of course when drifting about in the deep sea, but when they come into contact with a gently shelving coast and grate along the bottom. These mountains of ice, laden with the debris of the land, are often carried along with the velocity of from two to three miles and hour : and before their enormous momentum can be entirely de- stroyed, an extensive surface of rock must have been rounded, grooved, and scarred pretty much in the same way as by the action of a Glacier. There can be no failure of the grinding materials. During the process of melting the Iceberg is constantly turning over according as the centre of gravity shifts its position : and thus a new part of its surface with fresh angular blocks of stone, together with fresh masses of sand and gravel, is constantly brought into contact with the floor of the ocean. And this is not mere theory. All these phe- nomena may be witnessed any day on the shores of Baffin's Bay and Hudson's Bay, and along the coast of Labrador. Again the evidence of glacial action may be dis- covered in the materials themselves which have been transported by ice. Many of the large erratic blocks, after F 66 GEOLOGICAL THEORY OF having travelled immense distances, exhibit the same sharp angular appearance as if they had only just fallen down from the cliff on the mountain side. By this cir- cumstance they are at once distinguished from blocks of stone transported by running water ; for in these the angles are sure to be rounded off by friction. Sometimes, too, they are deposited not only far away from the same rock, but in regions where no rock of the same kind exists. In the case of Icebergs they are not unfrequently carried many hundreds of miles before being dropped into the depths of the ocean, and, in the course of their long journey, borne over the lofty ridges of submarine mountain chains. Furthermore, it often happens that a Glacier shrinks backwards up the valley, and sometimes even disappears altogether. When the melting of the ice at the lower extremity exactly balances its onward progress, then the Glacier seems stationary to the eye, and occupies from year to year the same position. But, when a number of hot seasons follow one another in immediate succession, the ice is melted more rapidly than the Glacier ad- vances, and in consequence it gradually becomes shorter, and seems to the eye to recede towards the upper parts of the valley. In this case the long lines of moraines, which before had rested on the ice, arc left spread out on the plains or deposited on the slopes of the moun- tain. Immense blocks of stone are by this means fre- quently set down on the summits of lofty crags, and in such Hke positions, to which they could not be brought by any other natural agency. These Perched Blocks, as AN ANCIENT GLACIAL PERIOD. 67 they are called, and also those long regular mounds of earth and stones abound in several of the Swiss valleys and constitute a very striking feature of Alpine scenery. Now it appears that all these various characteristic marks of glacial operations can be distinctly traced in many countries where the action of moving ice has been unknown within the period of history. And on this fact is founded the Geological theory of an ancient Glacial Period. We are confidently assured that a great ^art of Northern Europe, including even our own is- lands, not to speak of America and other countries as well in the northern as in the southern hemisphere, were, in some far distant age, the scene of those same pheno- mena which are witnessed at the present day amid the solemn grandeur of the Alps, and in the frozen wastes of the Arctic regions. In that age enormous Glaciers moved slowly downwards from snow-clad heights over innumerable valleys now rich with the fruits of the earth; ponderous Icebergs floated over wide areas of the ocean where now the dry land appears ; and vast piles of promiscuous rubbish, with great angular blocks of stone, were deposited on the slopes and crests of submarine mountains that now tower hundreds of feet above the level of the sea. To illustrate this theory we would begin with a country where the vestiges of glacial operations in past times may be studied side by side with the glacial phe- nomena of the present day. In Switzerland it needs but little skill to discern many marks and tokens of moving ice where moving ice is no longer found. In descend- F 2 68 GREAT MASSES OF ALPINE ROCKS ing, for example, the valley of the Hasli or the valley of the Rhone, the intelligent traveller can hardly fail to ob- serve how the rocks all around are scarred and furrowed, precisely after the same fashion as the rocks in the higher parts of the same valleys are now being scarred and furrowed by the Glacier of the Aar and the Glacier of the Ehone. At intervals, too, may be seen long mounds of unstratified gravel and mud, with large fragments of rock, in every way resembling the terminal moraines how daily accumulating at the extremities of existing Glaciers. When these facts are once distinctly brought home to the mind, it is impossible to resist the conclu- sion that several of the Alpine Glaciers once extended far beyond their present limits down the valleys of Swit- zerland. If we proceed a little distance to the mountains of the Jura, now wholly devoid of Glaciers, we shall find that the same glacial phenomena with which we have become so familiar in the Alps, are still everywhere presented to the eye. And we feel instinctively impelled to pursue the same line of inductive reasoning. Moving ice we know from abundant observation is capable of producing these effects : nor have we ever seen effects of this kind produced by any other cause : nay, there is no other natural -agent known that is capable of producing such effects : it is therefore reasonable to infer that moving ice was the cause of these effects ; and that, in some by- gone age, great masses of ice moved slowly over the vaUeys of the Jura as they now move slowly over the valleys of the Alps. DEPOSITED ON THE MOUNTAINS OF THE JUBA. 69 Another circumstance may here be noticed which is well worthy of consideration. The Alps are composed of granite, gneiss, and such like crystalline rocks : the Jura, of limestone and various other formations, altogether dif- ferent from those of the Alps. Now scattered loosely over the valleys of the Jura, and perched upon its lofty crests, we find immense angular blocks — some of them as large as cottages — of the Alpine rocks. The question naturally arises how have they been transported to their present site. Certainly not by the action of water : for in that case the projecting angles would have been rounded off, and the sharp edges worn away. But the work might have been easily accomplished by the power of moving ice, and could not have been accomplished by any other natural agency with which we are acquainted. Thus we are led to conclude that the Glaciers of the Alps must, by some means or another, have once made their way northwards across the great valley of Switzer- land, fifty miles wide, and deposited their ponderous burdens of gravel, sand, and erratic blocks on the moun- tains of the Jura. It would carry us too far from our present purpose to draw out this theory in all its details. But we cannot forbear briefly to touch upon some of the bold and start- ling conclusions to which it has led. The Geologist hav- ing by patient and varied exercise, in the regions of existing Glaciers, trained his eye and his judgment in the observation of those phenomena that mark the ac- tion of moving ice, soon begins to discover that they are not wanting in other countries. They are not to be 70 THE MOUNTAINS OF WALES found, indeed, beneath the burning sun of Africa, nor on the borders of the Mediterranean Sea. But as he travels northwards they begin by degrees to appear ; and when at length he reaches the shores of the Baltic, they are spread out profusely before him as they were in the bosom of the Alps. All this had puzzled Geolo- gists for years : but the clue has been found at last. What is going on to-day in Switzerland, and in Green- land, and on the shores of Labrador, must have been go- ing on, ages ago, in Germany, tod in Denmark, and on the shores of the Baltic. We may argue from the effect to the cause. Here are the moraines, the erratics, the perched blocks, and the surfaces of rock furrowed and scratched with ice : at some past time there must have been the moving Glaciers and the floating Icebergs. Following out this line of argument, and applying it to countries nearer home, Geologists have come to the conclusion that the Grampian Hills in Scotland, the mountains of Kerry in Ireland, the Snowdonian heights in Wales, and many other ranges of hills in these is- * lands were in former times subjected to the action of moving ice. Nay it is contended, with much show of reason, that these islands must have been, for a con- siderable time, in great part submerged beneath the sea, and traversed by floating Icebergs. When large erratic blocks are found in the immediate neighbourhood of the formation from which they have been derived, then it is easy to explain their origin and to trace their course. But it often happens that the nearest rock of the same mineral composition, and, therefore, the nearest rock ONCE TRAVERSED BY FLOATING ICE. 7 1 from which they can possibly have been derived, is sepa- rated from the site which they now occupy by a lofty chain of mountains. By what means, then, have they been transported hither ? Not by moving water ; for their sharp edges and projecting angles are still pre- served. Not by Glaciers ; for a Glacier cannot climb a steep mountain ridge. It would seem, indeed, that, in the present geographical distribution of land and water, there is no natural cause which could carry them from the parent rocks to their present position. But if we suppose that, in some long passed age of the world, Great Britain and Ireland were submerged beneath the sea, and that Icebergs floated in the waters above, the problem is solved at once. The fragments of far distant rocks frozen into the Icebergs might then have been carried over the summits of what are now lofty moun- tains, and, as the ice melted away, might have been de- posited all along their slopes and even on their highest crests. The presence of marine shells, belonging chiefly to species which now exist only in the arctic seas, aSbrds a strong confirmation of this hypothesis. For they are found intimately associated with the erratic blocks, not merely in valleys, to which the sea might be supposed to have had access in times of extraordinary flood, but upon lofty mountains at a height of five hundred, six hundred, and even thirteen hundred feet above the level of the sea. There is no difficulty in accounting for this pheno- menon if we suppose the country to have been at one time submerged, and the glacial drift in which the shells 72 DENUDATION AN ESTABLISHED FACT. are found imbedded to have been deposited by Icebergs on the floor of the ocean. If we refuse to make this sup- position the difficulty is simply insurmountable.' But it is somewhat beside our purpose to wander so far into the region of theory and speculation. Our main object in these chapters has been to establish the fact that Denudation is actually taking place to an almost incredible extent, in the present age of the world. For this purpose we have enumerated the principal agents by which this process is carried on : and we have en- deavoured to show from the authenticated researches of travellers and scientific men that they have been at work within the period of history, and are stiU at work around us. Our summary is, indeed, brief: but it is still sufficient to demonstrate that, even during the pre- sent age, the whole surface of the Globe has been ever in a constant state of change ; that mountain heights have been worn away, and valleys have been scooped out, and lofty cliffs have disappeared, and bold headlands have been rent in twain, and rocks and earths have day by day been broken up and dissolved and decomposed, by the never ceasing operation of natural causes ; and that the broken fragments are at every moment moving along over the surface of the land or through the depths of the sea. • Agassiz, Etudes bux les Glaciers ; Tyndall, Glaciers of the Alps ; also Heat as a mode of Motion, by the same Author; Lyell, Principles of Geology, vol. i. chapter xvi. ; Elements of Geology, chapters xi., xu. ; "Wallace, Ice Marks in North "Wales, in the Quarterly Journal of Science^ No. XIII. THE RAW MATERULS OF NEW STRATA. 73 Now Geologists tell us that these are the raw materials of a new building which is going on in these latter times under the guiding hand of Nature. Indeed, they say it is not so much a new building as the uppermost story of an old building. If we descend into the Crust of the Earth we may trace this building even from the founda- tions, which are laid upon the solid granite, up through each successive stage of limestone, and sandstone, slate, conglomerate, and clay, until we come to the surface, where new strata, composed of the same elements, and exhibiting the same general characteristics, are slowly growing up before our eyes. Thus will the idea gradu- ally steal upon the mind, that the works of ages long gone by are reproduced once again in our own days, and that we may study the history of the past in the mirror of the present which nature holds up to our view. This is the branch of Geological argument upon which we are now about to enter. We have visited Nature, as it were, in her quarry, and we have seen how she collects her materials, how she fashions them to her purpose, how she transports them to the place for which they are designed. If it be true, as alleged, that with these ma- terials she is actually engaged, at the present moment, in building upon the existing surface of our Globe a new series of stratified rocks, which are the exact counterpart of those beneath, this fact affords at least a very strong presumption in favour of one very important principle in the theory of Geologists. Let us, then, follow the course of her operations and judge for ourselves. CHAPTER V. STRATIFIED EOCKS OF MECHANICAL ORIGIN — THEORY DE- VELOPED AND ILLUSTRATED. FORMATION OF STKATIFIED BOCKS ASCRIBED TO THE AGENCY OP NA- TURAL CAUSES — THIS THEORY SUPPORTED BY PACTS — THE ARGUMENT STATED — EXAMPLES OP MECHANICAL ROCKS — MATERIALS OP WHICH THEY ARE COMPOSED — ORIGIN AND HISTORY OP THESE MATERIALS TRACED OUT — PROCESS OP DEPOSITION — PROCESS OP CONSOLIDA- TION — INSTANCES OP CONSOLIDATION BY PRESSURE — CONSOLIDATION PERPEOTED BY NATURAL CEMENTS — CURIOUS ILLUSTRATIONS — CON- SOLIDATION OP SANDSTONE IN CORNWALL — ARRANGEMENT OP STRATA EXPLAINED BY INTERMITTENT ACTION OP THE AGENTS OP DENUDA- TION. The Stratification of Rocks is one of the most remark- able features which the Crust of the Earth presents to our notice ; and the principles by which this phenome- non is explained belong to the very foundation of Geo- logical theory. It is now universally agreed that the successive layers or strata, which constitute such a very large proportion of the Earth's Crust, and which cannot fail to attract the notice even of the most careless ob- server, have been slowly built up during a long series of ages by the action of natural causes. In support of this bold and comprehensive theory geologists appeal to the operations which are going on in nature at the present day, or which have been observed and recorded within historic times. There is a vast machinery, they say. ORIGIN OF STRATIFIED ROCKS. 75 even now at work all over the world, breaking up the rocks that appear at the surface of the Earth, transport- ing the materials to different sites, and there construct- ing new strata, just the counterpart of those which we see piled up one above the other, wherever a section of the Earth's Crust is exposed to view. It is given to us, therefore, on the one hand to contemplate the finished work as it exists in the Crust of the Earth, and on the other, to examine the work still in progress upon its surface ; and if both are found to agree in all their most remarkable characteristics, it is not unreasonable to in- fer that the one was produced in bygone ages by the very same caiises that are now busy in the production of the other. In the examination of this argument we first turned our attention to the numerous and powerful agents that are now employed in the breaking up and transporting of existing rocks. It was impossible within our narrow limits to enumerate them all. But we selected those which are at the same time the most familiar in their ope- rations, and the most striking in their results : — mighty rivers discharging daily and hourly into the sea the ac- cumulated spoils of vast continents ; the breakers of the ocean dashing with unceasing energy against all the cliffs and coasts of the world ; the tides and currents of the sea taking up the ruins which the breakers have made, and carrying them far away to the lonely depths of the ocean ; the frozen rain bursting massive rocks asunder with its expansive force, and sending the frag- ments over lofty cliffs and steep precipices to become 76 DEMOLITION ^ND EECONSTKUCTION. the prey of roaring mountain torrents, or perhaps, more fortunate, to find a place of tranquil rest on the bosom of the glitter ing Glacier ; then this wondrous Glacier itself, a moving sea of ice, bearing along its ponderous burden from the summits of lofty mountains far down into the smiling plains, and meanwhile, with tremendous power, grinding, and furrowing, and wear- ing away the floor of the valley, and leaving behind it an impress which even time cannot efface ; and lastly, the massive Icebergs which stud the northern and south- ern seas, drifting along like floating islands above the fathomless abysses of the ocean, and scattering their huge boulders over the surface of submarine mountains and valleys. All these phenomena have been learned from actual and repeated observation. They are not philosophical speculations, but ascertained facts. We cannot doubt, therefore, that the work of demolition is going on ; it remains for us now to inquire about the work of recon- struction. The reader will remember that Geologists divide the stratified rocks into three distinct classes, Mechanical, Chemical, and Organic. This distinction, they say, is founded on the actual operations of Nature. From a close examination of the natural agents now at work in the world, it appears that some strata are being formed chiefly by the action of mechanical force ; others chiefly by the influence of chemical laws ; and others again chiefly by the intervention of organic life. Thus we have three distinct classes of rock at present coming EXAMPLES OF MECHANICAL ROCKS. 77 into existence, each exhibiting its own peculiar cha- racteristics, and each, moreover, having its counterpart among the strata that compose the Crust of the Earth. We shall now proceed to set forth some of the evidence that may be advanced in favour of these important con- clusions, beginning with those rocks that are called Me- chanical. And first it is important to have, at least, a general idea of the appearance which Mechanical Rocks present to the eye. We shall take three familiar examples, Con- glomerate, Sandstone, and Clay. Conglomerate or Pudding-stone, as it is sometimes called, is composed of pebbles, gravel, and sand, more or less compacted to- gether, and generally forming a hard and solid mass. The various materials of which it is composed, though united in the one rock, nevertheless retain their own external forms, and may be distinctly recognised even by the unpractised eye. Sandstone, as the name im- plies, is made up of grains of sand closely compressed and cemented together. The quality and appearance of this rock vary very much according to the size and character of its constituent particles. Often the grains of sand are as large as peas, or even larger ; sometimes they are so minute that they cannot be distinguished without the aid of a lens. For the most part they con- sist of quartz, with grains of limestone intermixed ; and they are. usually rounded as if by the action of running water. Clay is a rather vague and general term, now commonly employed to denote any finely divided mineral matter which contains from ten to thirty per cent of 78 VARIETIES IN THE FORM AND TEXTURE Alumina, and is thereby rendered plastic, and capable, when softened with water, of being moulded like paste with the hand. It occurs in many different forms among the strata of the Earth, according to the different minerals that enter into its composition and the diffe- rent influences to which it has been subjected. Marl and Loam may be taken as well known illustrations : the former is a clay in which there is a large proportion of calcareous matter ; the latter is a mixture of clay and sand. Sometimes by pressure clay is condensed into a kind of slaty rock called Shale, which has the property of being easily split up into an immense number of thin plates or laminae. It should be remembered that there is not always a perfect uniformity in the structure of these rocks. In Conglomerate, for example, the pebbles may be as large as cannon balls, or they may be only the size of walnuts. So, too, we have every variety of fineness and coarse- ness in the quality of Sandstone. Again, both Conglo- merate and Sandstone are often largely adulterated with clay, and on the other hand, clay will sometimes con- tain more than its usual proportion of sand or lime. Lastly, these materials are in one place compacted into hard and solid rock, in another they are found in a loose and incoherent condition. But amidst all these varieties of form and texture, the rocks we have been describing generally preserve their peculiar characteristics, and with a little experience can be easily recognised. They are found to constitute a very large part, perhaps we might say the larger part. OF MECHANICAL ROCKS. 79 of the stratified rooks in every country that has hitherto been explored by Geologists. Wherever we go we are met by the same familiar appearances ; — beds of Conglo- merate, Sandstone, Clay, Marl, Shale, recurring again and again through a series of many hundred strata, sometimes in one order, and sometimes in another; sometimes without any formation of a different kind intervening, and sometimes alternating with limestone or other rocks of which we shall speak hereafter. Such is the general character and appearance of those strata which are known among Geologists as Aqueous Eocks of Mechanical origin. Now it must at once strike the reader, that these rocks are made up of just those very materials — the same both in kind and in form — that we have already shown to be daily prepared and fashioned by a vast and complex machinery in the great workshop of Nature. He will remember how enormous blocks are detached from the mountain side, or from the cliffs on the sea-shore, and broken up into fragments ; how the fragments in time become pebbles, sand, and mud ; and how these are caught up by rivers, tides, and currents, and carried far away to sea. Here we have certainly all the materials that are necessary for the building up of Conglomerate, Sandstone, and Shale. We have seen how they are prepared by the hand of Nature, how they are moulded into shape, how they are transported from place to place. Let us now pursue the sequel of their history, and follow them on to the end. It is plain they cannot remain for ever suspended in 8o DEPOSITION OF STRATA. water ; sooner or later they must fall to the bottom. Yet they will not all fall together. For though all are carried downwards by the one force of gravity, those materials that are smaller and lighter will be more im- peded by the resistance of the water. The pebbles and coarse gravel will be the first to reach the bottom, then the sand, and last of all the fine impalpable mud. Thus, as the current sweeps along in its course, the sediment which it bears away from the land will be in a manner sorted, and three distinct layers of different materials will be deposited in the bed of the ocean ; — first, near- est to the shore, a layer of pebbles and coarse gravel, then a layer of sand, and last of all a layer of fine mud or clay. This is the first step in the construction of stratified rock. To complete the work nothing more is necessary than the consolidation of these loose and in- coherent materials. If this could be accomplished, then we should have a solid stratum of Conglomerate, a solid stratum of Sandstone, and a solid stratum of Shale formed in the bed of the ocean. With regard to this operation, however, we cannot hope for the advantage we have hitherto enjoyed, of actual observation. The process of consolidation, if it take place at all, is going on in the depths of the Sea, But though it is thus removed beyond the reach of our senses, it is not beygnd the reach of our intelligence. We may borrow the torch of Science, and search even into the hidden recesses of Nature's secret laboratory. In the first place, a partial consolidation of clay and sand, and even of gravel, may take place under the in- CONSOLIDATION OF STRATA. fluence of pressure alone. Many of us are familiar with this truth, but few perhaps are aware how extensively it is illustrated in the practical arts of life. Here are some curious and interesting examples. The minute fragments of coal which are produced by the friction of larger blocks against one another, and which may be obtained abundantly in the neighbourhood of every coal mine, are now manufactured into a solid patent fuel by the simple process of forcible compression. Again, the dust and rubble of black lead, formerly cast aside as useless, are now carefully collected, and by no other force than pressure are converted into a solid mass, fit to be employed in the manufacture of lead pencils. " The graphite or black lead of commerce," says Sir Charles Lyell, " 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 as com- pact 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 fit- tings. It is then struck several blows, each of a power of a thousand tons : after which operation the powder is so perfectly solidified that it can be cut for pencils, and exhibits when broken the same texture as native gra- phite." ' An instance yet more to our purpose occurs in the experiments made to try the force of gunpowder. Leathern bags filled with sand are put into the mortar I Elements of Geology, p. 38. G 82 ACTION OF MINERAL CEMENTS. that is to receive the cannon ball at a distance of fifty feet from the mouth of the gun ; and the sand is often com- pressed by the percussion of the ball into a solid mass of Sandstone.' Now the deposits of which we are speaking cannot fail to be subjected to a very powerful and a very constant compressing force. For since the process of de- position is always going on, the matter which is deposited to-day will to-morrow be covered with a new layer, and in the course of ages it may lie beneath an immense pile of mineral matter, hundreds or even thousands of feet in thickness. But in fact there is another and a more important agent at work. When the harder and more compact blocks of Conglomerate and Sandstone are subjectedto a close analysis in the laboratory of the chemist, it is found that they are strongly cemented together, sometimes by a solution of lime filling up the interstices between the grains or pebbles, sometimes by a solution of silica, sometimes by a solution of iron. Now this discovery afibrds a useful clue when we come to study the pre- sent operations of Nature. It is to the agency of a mineral cement we must look for the perfect consoli- dation of Mechanical Eocks. Let us see if such a cement can be found. It is well known that the water of rivers, lakes, and springs, is more or less charged with carbonic acid gas : and therefore, when it comes in contact with limestone, it dissolves a portion of the lime and holds it in solution. ' Mantell, Wonders of Geology, vol. i., p. 102. ACTION OF MINERAL CEMENTS. 83 Hence it follows that in every part of the world there exists an abundant store of calcareous cement. Again, our readers must have observed the brownish rusty- colour sometimes produced by streams on the surface of rocks and herbage. This is the result of the iron with which the streams are impregnated: and we are in- formed by scientific inquirers that water containing a solution of iron prevails very generally in almost all countries. The solution of silica in water is not so com- mon ; because pure silica cannot be dissolved by water except at a very high temperature. Nevertheless, it has been clearly demonstrated by observation, that silica, when it occurs in certain combinations with other mine- ral substances, may be dissolved readily enough : for instance, in the decomposition of felspar, and of all rocks in which felspar is an ingredient, silica is carried off in a state of solution.' And since these rocks are very numerous, and distributed over every part of the earth, we may fairly conclude that a solution of silica exists very abundantly in nature. Now when we bear in mind that we have on the one hand in the Crust of the Earth, solid strata of Conglo- merate and Sandstone, exhibiting the evident operation of these mineral cements ; and on the other hand, near the surface, the loose materials of Conglomerate and Sandstone as if ready to be cemented, and close at hand the cementing mineral itself in a convenient form, it is not unreasonable to assume that the process should ac- 1 Lyell, Klements of Geology, p. 4* ; also Principles, vol. i., p. 410. G 2 84 EXAMPLES OF CONSOLIDATION. tually take place ; — that water highly charged with iron, or lime, or silica, should filter through the loose gravel and sand, depositing its mineral cement as it passes along, and converting the newly formed strata into compact and solid rock. But this conclusion does not rest upon antecedent probability alone. We have proof unquestionable that a process such as we have described is actually going on. In the dredging of the river Thames large masses of solid Conglomerate are found from time to time firmly co'mpacted together by a ferruginous cement. And there is internal evidence that the process of solidification has been effected by natural causes within historic times ; for it happens not unfrequently that Roman coins and frag- ments of pottery are found imbedded in the solid block of stone. Similar discoveries were made in deepening the bed of the river Dove in Derbyshire, about the year 1832. Thousands of silver coins were found about ten feet under the surface, firmly cemented into a hard Conglomerate. Several of these coins bear dates of the thirteenth and fourteenth centuries ; and therefore the pebbles which form the rock must have been deposited and converted into a solid mass since that time. But we must not sup- pose that so long an interval is necessary for the conso- lidation of rocks. In the early part of the present cen- tury a vessel called the Thetis was wrecked off cape Frio on the coast of Brazil. A few months afterwards, when an attempt was successfully made to recover the dollars and other treasures which had gone to the bottom with the wreck, they were found completely enveloped in EXAMPLES OF CONSOLIDATION. 8S solid masses of quartzose Siandstone. The materials of the newly formed stone were In this case manifestly de- rived from the granitic rocks of the Brazilian coast.' In many parts of the Mediterranean and along its shores this process is known to be going on with equal rapidity. " The new-formed strata of Asia Minor," writes Sir Charles Lyell, " consist of stone not of loose incohe- rent materials. Almost all the streamlets and rivers, like many of those in Tuscany and the south of Italy, hold abundance of carbonate of lime in solution, and pre- cipitate Travertine, or sometimes bind together the sand and gravel into solid Sandstones and Conglomerates ; every delta and sand-bar thus acquires solidity, which often prevents streams from forcing their way through them, so that their mouths are constantly changing their position."'' In the Museum at Montpeller is exhibited a cannon Imbedded in a crystalline calcareous rock which was taken up from the bed of the Mediterranean near the mouth of the Rhone.' To these examples of the solidification of rock within recent times we are tempted to add one more, taken from a Memoir published by the late Dr. Paris in the Transactions of the Royal Geological Society of Corn- wall. " A sandstone occurs in various parts of the north- ern coast of Cornwall, which affords a most Instructive example of a recent formation, since we here actually detect Nature at work in converting loose sand into ' Mantell's Wonders of Geology, pp. 70, 81, 82, 83. » Lyell, Principles of Geology, vol. i. p. 43'- '- Id., ib., p. 429. 86 SOLIDIFICATION OF SANDSTONE IN CORNWALL. solid rock. A very considerable portion of the northern coast of Cornwall is covered with calcareous sand, con- sisting of minute particles of comminuted shells, which, in some places has accumulated in quantities so gr^at, as to have formed hills of from forty to fifty feet in ele- vation. In digging into these sand-hills, or upon the occasional removal of some part of them by the winds, the remains of houses may be seen ; and in places where the churchyards have been overwhelmed, a great num- ber of human bones may be found. The sand is sup- posed to have been originally brought from the sea by hurricanes, probably at a remote period. It first ap- pears in a state of slight but increasing aggregation on several parts of the shore in the Bay of St. Ives ; but on approaching the Gwythian River it becomes more extensive and indurated. ... It is around the promon- tory of New Kaye that the most extensive formation of Sandstone takes place. Here it may be seen in different stages of induration, from a state in which it is too friable to be detached from the rock on which it reposes, to a hardness so considerable that it requires a very violent blow from a sledge to break it. Buildings are con- structed of it ; the church of Cranstock is entirely built with it ; and it is also employed for various articles of domestic and agricultural uses." No reasonable doubt can, therefore, remain that the loose beds of gravel, sand, and clay, which, as we have already seen, are deposited from day to day, and from year to year, and from century to century, beneath the waters of the ocean, may be converted in the course of ORIGIN OF STRATIFICATION EXPLAINED. 87 time by natural agents into solid rocks of Conglomerate, of Sandstone, and of Shale. But this is not enough. It yet remains for us to explain how these solid rocks come to be arranged in a series of distinct layers or strata. The reader will remember that the supply of materials in any given area of the ocean is not fixed and con- tinuous, but, on the contrary, variable and intermit- tent. During the periodical rains within the tropics, and during the melting of the snows in high latitudes or in mountain regions, the rivers become enormously swollen, and carry down a far greater quantity of sedi- ment than at other seasons. The waste of cliffs, too, by the action of the waves, is much greater in winter than in summer. Thus while at one season a particular river or current may be comparatively free from sediment, at another it will carry along in its turbid course an almost incredible freight of mineral matter. We have a nota- ble example in the case of the Gangfes. The bulk of earthy matter which this river discharges into the sea, during the four months of rain, averages about 50,000,000 of cubic feet per day; whereas the daily discharge during the three months of hot weather is considerably less than one hundredth part of that amount.' Besides this variety in the quantity of materials car- ried, there is also a great variety in the velocity both of ' The figures given by Sir Charles Lyell and derived from the ohser- vations of Mr. Everest are these : total discharge during the four months of rain, 6,082,041,600 cubic feet; total discharge during the three months of hot weather, 38,154,240 cubic feet.— Principles of Geology, vol. i., p. 4S1. 88 ORIGIN OF STRATIFICATION EXPLAINED. rivers and of currents ; and therefore they will not al- ways carry the same materials to the same distance ; for the less rapid the stream, the sooner will the sediment fall to the bottom. We may add that currents, as is well known, often change their direction from various causes, and thus at different times they will carry the waste of the land to different parts of the ocean. From these considerations two conclusions may be fairly deduced : First, that the process of deposition may often go on very rapidly for a time over a given area, and then altogether cease, and after an interval begin again. In this way time may be allowed for one depo- sit to acquire more or less consistency before the next is superimposed ; and thus a succession of distinct beds will be produced. Secondly, we may infer that the same precise materials will not always be deposited over the same area ; at one time it will be sand, at ano- ther gravel, at another clay, at another some combina- tion of these or other mineral substances. And thus it may happen that the strata deposited in successive pe- riods of time shall not only be distinct one from the other, but composed of different materials;— that there shall be, in fact, as we so often see that there are, beds of Conglomerate, Sandstone, Clay, Marl, and other rocks, succeeding one another in every variety of order. CHAPTER VI. STRATIFIED ROCKS OF MECHANICAL ORIGIN — FURTHER ILLUSTRATIONS. IMPOSSIBLE TO WITNESS THE FORMATION OP STRATIFIED ROCKS IN THE DEPTHS OF THE OCEAN — ON A SMALI. SCALE EXAMPLES ARE EXHIBITED BY RIVERS AND LAKES — ALLUVIAL PLAINS — THEIR EX- TRAORDINARY FERTILITY — OUEAT BASIN OF THE NILE — EXPERIMENTS OF THE ROYAL SOCIETY — THE MISSISSIPPI AND THE ORINOCO — SOME RIVERS FILL UP THEIR OWN CHANNELS — -CASE OP THE EIVBR PO — ARTIFICIAL EMBANKMENTS — LARGE TRACT OF ALLUVIAL SOIL DEPO- SITED BY THE RHONE IN THE LAKE OF GENEVA DELTAS — THE DELTA OP THE GANGES AND BRAHMAPOOTRA — DELTA OF THE NILE. The argument set forth in the last chapter is simple, in- genious, and persuasive. Nay we must fairly confess that to us it seems conclusive. We do not mean to say that it amounts to a rigorous demonstration. But it af- fords at least a strong presumption that the process of deposition, the process of consolidation, and the process of stratification, are going on to a vast extent beneath the waters of the ocean ; and that, in these latter ages of the world's history, Aqueous Rocks are slowly growing up under the influence of natural causes, which resemble in every important feature those that are now attracting so much attention within the Crust of the Earth. We are therefore prepared to accept this conclusion, if it be not found at variance with any well-established fact, or with any known and certain truth. But in matters of physical science the evidence of our senses is, after all. 90 ALLUVIAL PLAINS. the most satisfactory argument. And our readers, no doubt, would like to witness, if possible, with their eyes the building up of Stratified Bocks. Now, though it is not given to us to see this process in all its colossal magnitude as it goes on within the depths of the mighty ocean, it is yet possible to behold it exhibited, as it were, in miniature, in certain cases where the sediment of rivers is deposited within reach of observation. Every one is familiar with the fact that many rivers overflow their banks at certain seasons, and spread them- selves out over a wide area, sometimes reaching to the foot of the hills that bound the valleys through which they flow. This is the origin of those Alluvial Plains so remarkable for their surpassing richness and fertility. In each successive year a thin film of sediment is depo- sited on the surface of the land; and thus in course of ages a soil is formed capable of producing, season after season, the most luxuriant crops without manifesting any symptoms of exhaustion. The soil of the Alluvial Plain near St. Louis on the Mississippi is thus spoken of by a modern traveller : " As to the quality of the land, any given number of crops might be grown off it. Corn has been raised on it for a hundred years toge- ther — as far back as the settlement is known. To in- quire about the system of farming in the West is not productive of information which would be of service on the continent of Europe. There is no system : the farmer scratches the ground and throws in the seed, and his bountiful harvests come up year after year without further thought or trouble. Thousands of centuries have GREAT BASIN OF THE NILE. 9 1 made the soil for him, and it defies him to make too heavy demands upon it. It gives him all he asks and is never known to disappoint or fail."' The great basin of the Nile offers an admirable ex- ample of an Alluvial Plain on a scale of considerable magnitude. Even in the days of Herodotus Egypt was regarded as the " gift of the Nile :" and the correctness of this opinion has been placed beyond all reasonable doubt by the investigations of modern science. The river bears along in its current, especially during the flood season, a large quantity of fine earthy sediment obtained by the process of Denudation from the mountains of central Africa. Once a year, between the months of July and November, it overflows its banks, and this se- diment is deposited on the adjoining plains. Thus a new layer of rich soil is spread out every year over the existing surface ; and the whole country is, in a man- ner, growing upwards at the average rate, according to a rough estimate, of about six inches in the century. Near Cairo, where excavations have been made, the successive layers of annual deposit are distinctly visible to the eye. And it is worthy of remark that, although each one of these is no thicker than a sheet of paste- board, the stratum of alluvial soil which overlies the sands of the desert, and which to all appearance has come into existence by the very same process, is often forty, fifty, and even sixty feet in depth. A series of interesting observations and experiments • From a Special Correspondent, in the Times Newspaper, December 7, 1866. 92 EXPERIMP^NTS OF THE ROYAL SOCIETY. have been recently made under the auspices of the Royal Society, which afford some useful information on this subject. The colossal statue ofRameses, near Memphis, was found to be partly imbedded in a stratum of mud which had gradually accumulated around it. Upon sinking a shaft, it was discovered that from the present surface of the plain to the base of the pedestal is a dis- tance of nearly ten feet. Now Eameses flourished, ac- cording to Lepsius, about one thousand three hundred and sixty years before the Christian Era : and therefore, since that time, or within a space of 3200 years, it is pretty clear that a thickness of ten feet has been added at this spot to the Alluvial Plain of the Nile. It is hard to resist the conclusion that the next stratum of ten feet as we proceed downwards, which in every re- spect resembles the first, must have been produced in the same way by natural causes : and so on till we reach the barren sand of the desert, which is here just forty- two feet below the present level of the plain.' It should seem, therefore, that Egypt is nothing more than a great Alluvial Plain, slowly built up in the long lapse of ages by the annual inundations of the Nile. Vast tracts of the same kind are to be found in other parts of the world. The Mississippi, which drains about one seventh of the whole North American continent, has formed an Alluvial Plain more than a thousand miles in length, and from thirty to eighty in breadth. And in South America the Orinoco once a year spreads out its 'Horner, Alluyial Land of Egypt, Phil. Trans, part i. for 1855; Lyell, Principles of Geology, vol. i. pp. 43 1 - 9. DESERTED RIVER COURSES. 93 swollen and turbid waters over an area not unfrequently seventy miles broad ; leaving behind, when it subsides, a substantial layer of muddy sediment to enrich the soil.' It would be easy to accumulate examples. But we shall be content with having referred the reader to the Great Basin of the Nile which affords special op- portunities for the study of alluvial phenomena ; being illustrated at once by the historical monuments of re- mote antiquity and the scientific researches of recent times. There is another process by which Alluvial Plains are formed. It often happens that a river fills up the channel in which it has been moving for years, and is forced to shift its course and seek a new passage to the sea. In progress of time this channel is tilled up like the former and deserted, and then a third, and then a fourth. At each change a new stratum is formed, almost always distinguished for its extraordinary ferti- lity. This phenomenon is chiefly to be looked for when an extensive and almost level plain lies between some lofty range of mountains and the sea. In such a case, the river which bears away the waste of the mountains, will move onward in its course with a sluggish current, and will, of necessity, deposit the greater part of its burden on the way. There is scarcely a country in the world that does not abound in formations of this kind ; and we could point to many notable instances in which herds of cattle are now grazing on the very spot where, The English Cyclopsedia, Alluvium. 94 EXAMPLE FROM THE RIVER PO. within quite recent times, the turbid waters of some great stream flowed sullenly along. The river Po, which receives through a thousand mountain torrents an enormous quantity of mineral sedi- ment from the Alps, affords an instructive example. Since the beginning of the fifteenth century it has many times changed its course, often committing great devastation, and always leaving behind unmistakable traces of its movements. Several towns that once stood on the left bank of the river are now on the right. In some in- stances parish churches and religious houses were pulled down when the devouring stream was seen slowly to approach, and then rebuilt with the same materials at a greater distance. An old channel may be easily recog- nized at the present day near Cremona, which bears the name of Po Morto, and another, called Po Vecchio, in the territory of Parma. It may be interesting to our readers to learn that these movements have been checked in modern times. By a system of artificial embankment the waters of the river are now confined within definite and narrow limits : thus the velocity of the current is increased, and a very considerable portion of the sediment is carried on to the sea. Nevertheless, much is still deposited in the bed of the river, which is in consequence raised higher and higher each successive year. Hence it has become necessary, in order to prevent inundations, to add every season to the height of the embankments, so that the river now presents the appearance of an enormous aque- duct, of which some idea may be formed from the fact ALLUVIAL PLAIN IN THE LAKE OF GENEVA. pj that, in the neighbourhood of Ferrara, the surface of the stream is higher than the roofs of the houses. This sys- tom of embankment is carried on very extensively in Northern Italy to check the overflowing of rivers, and to prevent them from changing their courses. It is as old as the time of Dante, who tells us that the inhabitants of Padua erected barriers along the Brenta when the snows began to melt and the season of the floods was approach- ing. " Per difender lor Tille e lor oastelli, Anzi che Chiarentana il oaldo senta." Inferno, Canto xv. As a river sometimes fills up its own channel, so too may it fill up a lake through which it flows, and convert it likewise into a great Alluvial Plain. Thus it is said several extensive lakes have been transformed into dry land in modern times near Parma, Piacenza, and Cre- mona. Elsewhere the process may be seen in actual operation. The Rhone when it enters the lake of Ge- neva is a turbid discoloured stream ; the natural con- sequence of the immense quantity of earthy sediment with which it is charged. But as it slowly moves along, the sediment falls to the bottom, and when, at length, " by Leman's waters washed," it emerges at the town of Geneva, and shoots beneath the magnificent bridge that joins the opposite shores, it has already as- sumed that beautiful azure blue which travellers love to gaze on, and poets love to sing. The sediment left behind goes to form a great alluvial tract which is slowly but steadily advancing into the lake. An ancient town called g6 DELTAS. Port Vallais, which, eight centuries ago, stood at the water's edge, is now a mile and a half inland. And if the world were to last long enough, and the natural agents at present in operation were to remain un- changed, the time would come, we can scarcely doubt, when the whole lake of Geneva would have been con- verted into an Alluvial Plain of vast extent and inex- haustible fertility. This last example leads us on to the phenomenon of Deltas, which afford, perhaps, the best opportunity of observing the actual formation of stratified rocks. Some large rivers, as we have already seen, enter the sea with such extreme velocity as to bear away their sediment to a distance of several hundred miles from the land. But in other cases the onward rush of the stream is much sooner arrested, and the sediment, if it be not caught up by ocean currents, is deposited near the mouth of the river, and forms a triangular tract of alluvial land. This kind of deposit is called a Delta from the resemblance it bears to the letter (A) of that name in the Greek Al- phabet. The apex of the triangle points up the stream, the base is towards the sea. Hence, when a Delta is formed the river naturally divides into two branches, one flowing to the right, the other to the left. In pro- gress of time new channels are almost always made, and the great stream empties itself into the sea by many mouths. The Delta formed in the Bay of Bengal by the two great rivers of India, the Ganges and the Brahmapootra, offers an illustration of this phenomenon on a scale of DELTAOF THK GANGES. 97 unusual magnitude. Indeed, strictly speaking, it is not one Delta only, but rather two Deltas lying side by side ; the one deriving its origin from the Ganges, the other from the Brahmapootra. This double Delta extends its base for two hundred and fifty miles along the Bay of Bengal, and stretches inwards into the continent of India to an almost equal distance. Here then is a vast tract of country manifestly composed of earthy sediment, ob- tained by the process of Denudation from the Hima- layan mountains, and afterwards transported to its present site by the agency of moving water. But the deposition of earthy matter does not suddenly come to an end when we reach the present line of the coast. The sea is vi- sibly discoloured by the sediment far beyond the actual base of the Delta ; and a sloping bank of mud is found to stretch beneath the waters of the Bay to a distance of a hundred miles. Even within the short period of a man's life the do- main of dry land is often visibly enlarged. Sandbanks are first formed in some of those numerous winding channels through which the two rivers find their way to the sea. The sandbanks, receiving fresh accessions dur- ing each succeeding flood, in a short time become is- lands; and the islands have been known, in a few years, to attain a superficial extent of many square miles. Then begins to appear a wild and luxuriant vegetation- reeds, long grass, shrubs, and trees ; and those impene- trable thickets are formed to which the buffalo, the rhi- noceros, and the tiger soon resort for shelter. A very extensive tract of this kind, adjoining the sea-coast, and H 98 DELTA or THE NILE. known as the Sunderbunds, is said to be as large as the principality of Wales. The Delta of the Nile, though not quite one-half as large as the Delta of the Ganges, presents nevertheless some features of peculiar interest. In many places where a vertical section is exposed to view, the pheno- menon of stratification may be distinctly recognized. The upper part of the deposit belonging to each year is composed of earth of a lighter colour than the lower part ; and the whole forms a distinct layer of hardened clay, which may be easily separated from those above and below. This formation, therefore, corresponds exactly with those strata of shale which we so often meet with in the Crust of the Earth. Again, many of the old channels through which the Nile made its way to the sea in ancient times, have been since filled up and con- verted into solid land. The two extreme arms of the river, which formerly enclosed the Delta, were two hun- dred miles apart where they entered the Mediterranean. But these channels are now Alluvial Plains, and the base of the Delta is but ninety miles in length. Hence, though the quantity of land which has been formed by the sediment of the Nile is much greater now than it formerly was, the size of the Delta properly so called has not been increased but diminished. If we turn to the great continent of America, we are met by results not less striking and important. The Delta of the Mississippi is two hundred miles in length, and one hundred and forty in breadth. This vast stratum of mud is between five and six hundred feet thick, and DELTA OF THE MISSISSIPPI. 99 covers an area twelve thousand square miles in extent. Each year it receives from the great Father of Rivers a new accession of sediment which is computed at 3,700,000,000 of cubic feet. And besides this annual deposit of inorganic matter, we must not omit from our estimate the countless trees of various species and of gigantic size, which are torn up by the floods, carried along by the impetuous stream, and buried at last with the bones of animals, and works of human art, and other spoils of the land, in the mud of the Delta at the river's mouth.' ' Lyell, Principles of Geology, vol. i. chapters xviii., xix. H2 CHAPTER VII. STRATIFIED ROCKS OF CHEMICAL ORIGIN, CHEMICAL AQENCT EMPLOYED IN THE POEMATION OE MECHANICAL BOCKS — BUT SOME KOCKS PRODUCED ALMOST EXCLUSIVELY BY THE ACTION OP CHEMICAL LAWS— DIPFERENCE BETWEEN A MIXTURE AND A SOLUTION — ^A SATURATED SOLUTION — STALACTITES AND STALAG- MITES — PANTASTIC COLUMNS IN LIMESTONE CAVERNS— THE GROTTO OF ANTIPAROS IN THE GRECIAN ARCHIPELAGO — WYER'S CAVE IN THE BLUE MOUNTAINS OP AMERICA — TRAVERTINE ROCK. IN ITALY — GROWTH OP LIMESTONE IN THE SOLPATARA LAKE NEAR TIVOLI — INCRUSTATIONS OP THE ANIO — FORMATION OP TRAVERTINE AT THE BATHS OP SAN PILIPPO AND SAN VIQNONE. The Aqueous Eocks of which we have spoken in the last two chapters are called by Geologists Mechanical ; inas- much as they owe their existence chiefly to the agency of Mechanical force. It should be observed, however, that a very considerable share in the production of these Eocks must be ascribed, not unfrequently, to Chemical influence. Chemical action helps to prepare the mate- rials of which they are composed : and Chemical action likewise furnishes the calcareous, siliceous, and other mineral cements by which they are, in a great measure, consolidated. There is, however, a second class of Aqueous Eocks which are produced almost exclusively by the operation of Chemical laws, and which we have accordingly denominated Stratified Rocks of Chemical Origin. It is of these that we purpose to speak in the present chapter. They constitute a much smaller pro- A MIXTURE AND A SOLUTION. lor portion of the Earth's Crust than either the Mechanical or the Organic Rocks. But the history of their forma- tion is curious and instructive. We shall confine our- selves to one or two simple and familiar illustrations. In the course of these illustrations we shall have a good deal to say about Carbonate of Lime in a state of solution : and it may perhaps be useful to explain, first of all, what is meant by a solution, in the technical lan- guage of Chemistry. If a spoonful of salt is put into a tumbler of water, the particles of salt, after a little time, cease to cohere together, and become so diffused through the water as to be no longer visible to the eye, although their presence in every part may be easily discerned by the taste. The salt is then said to be dissolved, and the water in which it is dissolved is called a solution of salt.. It is important to distinguish the case of a solution from the case of a mere mechanical mixture. If, instead of the salt, we were to put into the tumbler of water a spoon- ful of very fine sand, then we should have a mixture but not a solution. By stirring briskly the contents of the tumbler we might, indeed, effect a very close union be- tween the particles of water and the particles of sand : but this union would be altogether different in kind from the union that was observed in the former case be- tween the particles of water and the particles of salt. First, the sand would remain visible to the eye, making the water turbid and discoloured ; whereas the salt en- tirely disappeared, leaving the water limpid and transpa- rent as before. Again, ifthe water be allowed to rest I02 ORIGIN OF CHEMICAL ROCKS EXPLAINED. the sand will in time fall to the bottom, whereas the salt will not. But there is a limit to the capacity of water for holding salt in solution. If spoonful after spoonful be added, it will be found, when a certain point has been reached, that the water can at length dissolve no more. It is then called a saturated solution of salt. If, in this case, a portion of the water were to pass away by eva- poration, it is clear, we should have the same quantity of salt as before, in a smaller quantity of water. The consequence would be that all the salt could not then be held in solution, and some of it would fall to the bottom ; or, in chemical language, a precipitate of salt would be formed on the bottom of the tumbler. Now, according to the theory of Geologists, many rocks, hun- dreds of feet thick, and solid enough to form the walls of our palaces, our churches, and our castles, have been produced in the Crust of the Earth by just such a pro- cess as this. In support of their theory we are about to show that the process is actually going on in our own time, and is open to the examination of all who may desire to study it for themselves. We shall begin with the formation of Stalactites and Stalagmites. The mode in which these singular masses of rock are brought into existence is very clearly ex- plained, and the picturesque appearance they so often" present to the eye is very graphically described, by Doctor Mantell in his Wonders of Geology, from which the following passages are taken :— " One of the most common appearances in limestone caverns is the forma- STALACTITES AND STALAGMITES. tion of what are called Stalactites, from a Greek word signifying distillation or dropping. Whenever water filters through a limestone rock it dissolves a portion of it; and on reaching any opening, such as a cavern, oozes from the sides or roof, and forms a drop, the moisture of which is soon evaporated by the air, and a small circular plate or ring of calcareous matter remains ; another drop succeeds in the same'place, and adds, from the same cause, a fresh coat of incrustation, In time, these successive additions produce a long, irregular, co- nical projection from the roof, which is generally hol- low, and is continually being increased by the fresh accession of water, loaded with calcareous or chalky matter: this is deposited on the outside of the Stalac- tite abeady formed, and, trickling down, adds to its length by subsiding to the point, and evaporating as before ; precisely in the same manner as, during frosty weather, icicles are formed on the edges of the eaves of a roof. When the supply of water holding lime in so- lution is too rapid to allow of its evaporation at the bottom of the Stalactite, it drops on the floor of the cave, Und drying up gradually, forms in like manner a Stalactite rising upwards from the ground, instead of hanging from the roof ; this is called for the sake of dis- tinction Stalagmite. "It frequently happens, where these processes are uninterrupted, that a Stalactite hanging from the roof, and a Stalagmite formed immediately under it from the * superabundant water, increase until they unite, and thus constitute a natural pillar, apparently supporting the 104 GROTTO OF ANTIPAROS. roof of the grotto. It is to the grotesque forms assumed by Stalactites and these natural columns, that caverns owe the interesting appearances described in such glow- ing terms by those who witness them for the first time. One of the most beautiful stalactitic caverns in England is at Clapham, near Ingleborough. In the Cheddar Cliifs, Somersetshire, there has been discovered a similar cave richly incrusted with sparry concretions. There are others in Derbyshire. " The Grotto of Antiparos in the Grecian Archipelago, not far from Paros, has long been celebrated. The sides and roof of its principal cavity are covered with im- mense incrustations of calcareous spar, which form either Stalactites depending from above or irregular pillars rising from the floor. Several perfect columns reaching to the ceiUng have been formed and others are still in progress, by the union of the Stalactite from above with the Stalagmite below. These, being composed of mat- ter slowly deposited, have assumed the most fantastic shapes ; while the pure, white, and glittering spar beau- tifully catches and reflects the light of the torches of the visitors to this subterranean palace, in a manner*which causes all astonishment to cease at the romantic tales told of the place — of its caves of diamonds and of its ruby walls ; the simple truth, when deprived of all ex- aggeration, being sufficient to excite admiration and awe. " Sometimes a linear fissure in the roof, by the direc- tion it gives to the dropping of the lapidifying water, forms a perfectly transparent curtain or partition. A WYER's cave in the blue mountains. 105 remarkable instance of this kind occurs in a cavern in North America called Wyer's Cave. This cave is situ- ated in a ridge of limestone hills running parallel to the Blue Mountains. A narrow and rugged fissure leads to a large cavern, where the most grotesque figures, formed by the percolation of water through beds of limestone, present themselves, while the eye, glancing onward, watches the dim and distant glimmers of the lights of the guides — some in the recess below, and others in the gal- leries above. Passing from these recesses, the passage conducts to a flight of steps that leads into a large cavern of irregular form and of great beauty. Its di- mensions are about thirty feet by fifty. Here the incrus- tations hang just like a sheet of water that was frozen as it fell ; there they rise into a beautiful stalactitic pil- lar ; and yonder compose an elevated seat, surrounded by sparry pinnacles. Beyond this room is another more irregular, but more beautiful ; for besides having sparry ornaments in common with the others, the roof overhead is of the most admirable and singular formation. It is entirely covered with Stalactites, which are suspended from it like inverted pinnacles ; and they are of the finest material, and most beautifully shaped and embossed. In another apartment an immense sheet of transparent Stalactite, which extends from the floor to the roof, emits when struck deep and mellow sounds like those of a muffled drum. " Farther on is another vaulted chamber, which is one hundred feet long, thirty-six wide, and twenty-six high. Its walls are filled with grotesque concretions. The I06 WYER'S cave in the blue MOUNXA.INS. effect of the lights placed by the guides at various ele- vations, and leaving hidden more than they reveal, is extremely fine. At the extremity of another range of apartments, a magnificent hall, two hundred and fifty feet long, and thirty-three feet high, suddenly appears. Here is a splendid sheet of rock-work running up the centre of the room, and giving it the aspect of two se- parate and noble galleries. This partition rises twenty feet, above the floor, and leaves the fine span of the arched roof untouched. There is here a beautiful con- cretion, which has the form and drapery of a gigantic statue ; and the whole place is filled with stalagmitical masses of the most varied and grotesque character. The fine perspective of this room, four times the length of an ordinary church, and the amazing vaulted roof spreading overhead, without any support of pillar or column, produce a most striking effect. In another apartment, which has an altitude of fifty feet, there is at one end an elevated recess ornamented with a group of pendant Stalactites of unusual size and singular beauty. They are as large as the pipes of a full-sized organ, and ranged with great regularity : when struck they emit mellow sounds of various keys, not unlike the tones of musical glasses. The length of this extraordinary group of caverns is not less than one thousand six hundred feet." In the case of Stalactites and Stalagmites the actual formation of limestone by the influence of Chemical ac- tion is brought home forcibly to the mind, and, in a manner, made palpable to the senses. We shall now TRAVERTINE, THE BUILDING STONE OF ROME. 107 pass to Other examples in which the process is scarcely- less open to observation, and in which the limestone as- sumes a somewhat more massive and rock-like form. Every one who has been in Italy is familiar with the limestone rock called Travertine. It is seen in the an- cient walls and the venerable temples of Psestum, which have withstood unharmed the wasting hand of time for upwards oftwenty centuries. In Rome, too, this stone is associated in our minds as well with the enduring mo- numents of antiquity, as with the imposing splendour of Christian art. The Coliseum, the most stupendous of ruins, and St. Peter's, the most sublime of temples, are built of Travertine. In fact it seems to have been, in every age, the chief building stone employed in the ar- chitecture of the Eternal City ; and the quarries from which it was taken in ancient times may still be seen at Ponte Lucano, near Tivoli. Now it is an interesting fact, that close to this very spot, at the Solfatara lake on the one side, and at Tivoli itself on the other, the forma- tion of Travertine is going on in our own time, by the precipitation of lime from a state of solution. The Solfatara lake, situated about fourteen miles from Rome, on the road to Tivoli, is supplied with an un- failing stream of tepid water, impregnated with carbonic acid gas and saturated with carbonate of lime. The amount of carbonate of lime which the water is capable of holding in solution depends chiefly on three things : first, on the presence of carbonic acid ; secondly, on the high temperature of the water ; and thirdly, on its quan- tity. Now the carbonic acid is ever rising in bubbles Io8 EXPERIMENT OF SIR HUMPHREY DAVY. to the surface and passing away ; the temperature of the water is lowered by contact with the coaler atmosphere ; and its quantity is diminished by evaporation. Thus the capacity which the water at first had for holding the carbonate of lime in solution is notably diminished, and a part of the lime is precipitated to the bottom in a solid form, or clings to the vegetable matter with which it comes in contact. A very simple and interesting experiment, made in the early part of the present century by Sir Humphrey Davy, will illustrate the rapidity with which the forma- tion of solid stone is even now taking place. In the month of May he fixed a stick in the bed of the lake, and left it standing until the following April, when he found that it was covered with an incrustation of limestone several inches thick. ^ In precisely the same way new layers of Travertine are annually deposited in the bed of the lake, and incrusted on its rocky margin ; and so the lake itself is becoming smaller and smaller from year to year. We are told that in the middle of the seventeenth century it was a mile in circuit, and now it is little more than a quarter of a mile.^ Here, therefore, we have an immense mass of compact limestone rock, built up by natural agents within the last two centuries. At Tivoli, about four miles beyond the Solfatara, and two miles from the quarries of Ponte Lucano, phenomena of the same kind are exhibited. The waters of the Anio, which are saturated with carbonate of lime, form incrus- 1 Consolations in Travel, p. 127. 2 Handbook of Rome and its EnTirona : Murray, 1858, p. 315. FORMATION OF LIMESTONE IN TUSCANY. 109 tations oi Travertine on the banks of the river ; and at the celebrated falls, where the whole volume of the stream leaps at a bound from a height of three hundred and twenty feet, the most beautiful stalactites are formed by the foam. The formation of Travertine is going on with no less activity in other parts of the Italian Peninsula. At the baths of San Filippo, in Tuscany, there are three warm springs which contain a very large amount of mineral matter in solution. The water which supplies the baths falls into a pond where it has been known to deposit a solid stratum of rock thirty feet thick in twenty years. In the same neighbourhood are the mineral baths of San Vignone. The source from which the water flows is situated on the summit of a hill not more than a few hundred yards from the Jiigh road between Sieima and Rome ; and so rapid is the formation of stone, that half a foot of solid Travertine is deposited every year in the pipe that conducts the water to the baths. At this spot we have a very good illustration of the argument we are now considering. As the stream of water flows down the slopes of the hill, a thin layer of Travertine rock is pro- duced on the surface of the earth, almost before our eyes ; and so it was previous to our own time, and so it has been for ages, as history and tradition testify. The quantity produced in each year and in .each century is comparatively small, but we can have no doubt that it has been produced by the means described. Now, be- neath the surface of the Earth, immediately below these modern formations, of which we have so clearly ascer- no INFERENCE OF GEOLOGISTS. tained the origin, we find strata of the same kind, com- posed of the same materials, and arranged in the same way, layer resting upon layer, down to a depth of two hundred feet: and the Geologist accounts for the for- mation of the one according to the same laws which he has seen at work in the production of the other.' ' Lyell, Principles of Geology, vol. i. 400-3. CHAPTEK VIII. STRATIFIED EOCKS OF ORGANIC ORIGIN— ILLUSTRATIONS FROM ANIMAL LIFE. NATDKE OP OBQANIO EOCKS CAKBONATE OP IIMB EXTRACTED PBOM THE SEA BT THE INTEBVENTION OF MINUTE ANIMALCULES — CHALK EOCK — ITS VAST EXTENT— SUPPOSED TO BE OP ORGANIC ORIGIN — A STRATUM OP THE SAME KIND NOW GEOWINO UP ON THE FLOOR OP THE ATLANTIC OCEAN — CORAL REEFS AND ISLANDS — THEIR GENERAL APPEARANCE — THEIE GEOGRAPHICAL DISTEIEUTION — THEIR ORGA- NIC ORIGIN STEUCTUEE OP THE ZOOPHYTE — TAEIOUS ILLUSTRA- TIONS — AGENCY OP THE ZOOPHYTE IN THE 00N3TBUCTI0N OF COEAL BOCK — HOW THE SUNKEN EEEP IS CONVERTED INTO AN ISLAND — AND PEOPLED WITH PLANTS AND ANIMALS — DIFFICULTY PEOPOSED AND CONSIDERED — HYPOTHESIS OF MR. DARWIN — CORAL LIMESTONE IN THE SOLID CEUST OP THE EARTH. We now pass to the third division of Aqueous Rocks, those, namely, which are believed to have come into existence chiefly through the agency of animal and ve- getable life, and are therefore called Organic. The study of these rocks has been prosecuted with no inconsidera- ble ardour during the last thirty years ; and the facts which have been brought to light are certainly amongst the most curious and interesting in the whole range of physical science. Indeed we are convinced that a simple narrative of the researches which have recently been made upon this subject, and the discoveries to which these researches have led, would be no less attractive, and scarcely less wonderful, than a fairy tale. But it is 112 not for us to wander at large over this vast and tempting field of inquiry. We must be content with one or two examples, which may help to illustrate the process of inductive reasoning upon which the general principles of geological science are founded. It is argued, then, that the present operations of Na- ture afford the best key for the interpretation of her works in bygone times. We observe various beds of rocks now in course of formation on the surface of the Earth ; and within the Crust of the Earth we discover corresponding strata of the self same rocks already com- plete, and laid by, as it were, in Nature's storehouse. Side by side, therefore, we may study and compare the finished work and the work that is yet in progress ; and if, on a close examination, they are found to agree in all essential characters, we have doubtless a strong presump- tion, that the same causes which are now producing the one, must in former times have produced the other. This line of argument we have already considered in re- ference to those two classes of Aqueous Rocks which are said to be respectively of Mechanical and of Chemical origin. We now proceed to show that it is no less ap- plicable to those which are called Organic. And although we may not hope to unfold all the secret wonders of Nature's laboratory, that have come to light in recent times, yet we may afford a passing glimse at her opera- tions, which can scarcely fail to be interesting and in- structive. We have shown how strata of solid rock are sometimes formed in lakes by the precipitation of lime from a state THK KEY TO HER WORKS IN PAST AGES. 113 of solution. Now this process cannot take place in the sea ; for though lime is present in the sea, the quantity of carbonic acid with which it is there associated, is far more than sufficient to render its precipitation impos- sible.' But Nature has another contrivance for gather- ing together the solid elements of her building. The depths of the ocean are teeming with life : and countless tribes of minute animals are furnished with the power of extracting the lime from the waters they inhabit, and of reproducing it under a new form. Sometimes, through this mysterious operation of organic life, the lime is con- verted into a calcareous shell, like that of the oyster ; sometimes into a stony skeleton, as in the case of the nu- merous families of coral-producing animalcules. After death the soft fleshy substance of these animals melts away and disappears ; but the limestone shells and ske- letons remain, accumulating during the long course of ages to an almost incredible extent. And, if we are to believe Geologists, out of these accumulated materials, sometimes preserving their original form and structure, sometimes altered more or less by chemical action, some- times broken up into fragments by mechanical force, has been produced a very large proportion of the lime- stone rocks which occur so abundantly in the Crust of the Earth. No better illustration can be found than the white earthy limestone familiar to every one under the name of Chalk. An undulating stratum of Chalk Rock, attaining ' Jukes, Manual of Geology, p. 127. I 114 ■ CHALK BOCK OF EUROPE. not unfrequently a thickness of one thousand feet, may be said, speaking roughly, to underlie the south-eastern half of England. Sometimes it appears at the surface : sometimes it dips downwards, and forms a kind of great basin, over which are regularly spread out various other groups of Stratified Rocks. On the southern coast it rises to a height of several hundred feet above the level of the sea in a line of perpendicular cliffs, conspicuous from a distance by their dazzling whiteness. But the White Chalk of England is only an insignificant part of a great rook-formation, which may be traced over ex- tensive areas throughout all Europe, from Ireland to the Crimea, from the Baltic Sea to the Bay of Biscay ; and which everywhere preserves in a remarkable degree the same mineral character, and presents to the eye the same general appearance. Now it had often been suggested by Geologists that this wide-spread formation derived its existence chiefly from the accumulated remains of organic life. For in many instances the broken shells of minute animalcules could be distinctly observed to constitute a part of the rock. And even where the organic structure could not be so clearly traced, the carbonate of lime composing the Chalk presented just that appearance which would naturally result from the decomposition of such shells. This theory, however, was long put forward with diffi- dence and received with incredulity. Even scientific men found it hard to persuade themselves that a solid rock of such great extent and thickness could have been the work of agents apparently so insignificant. But it ATLANTIC SOUNDINGS. "S has been confirmed and illustrated in a very interesfing and unexpected manner within the last few years. When the project of connecting Europe apd America by a telegraph cable was first set on foot, it became ne- cessary to ascertain, as far as possible, the general con- figuration of the ocean bottom and the exact nature of the bed on which the cable was to lie. Accordingly in the year 1857 ^^ expedition was fitted out for this purpose under the command of Captain Dayman ; and a careful series -of soundings was taken between Valentia, on the West Coast of Kerry, and Trinity Bay on the shores of Newfoundland. It was found that the floor of the ocean between Ireland and America is a vast irre- gular plain, and that by far the greater part is covered over with a kind of soft mud or ooze. Samples of this ooze were scooped up, even at the most profound depths, by means of an ingenious apparatus attached to the sounding lines, and brought undisturbed to the surface. Afterwards they were carried home to England and sub- mitted for examination to Professor Huxley. The result has been to show that the materials of a limestone rock, resembling in every essential feature the White Chalk of Europe, are being spread out at the present day over an area of immense extent on the floor of the Atlantic Ocean. With the permission of our readers we shall allow Professor Huxley, as far as may be, to tell his own story.' As to the ocean floor itself, " It is," he says, " a prodi- ' See his Lecture Ou a Piece of Chalk, delivered during the Meeting of the British Association at Norwich, i868. I 2 1 1 6 BED OF THE ATLANTIC OCEAN. gious plain — one of the widest and most even plains in the world. If the sea were drained off, you might drive a wagon all .the way from Valentia to Trinity Bay. And, except upon one sharp incline about two hundred miles from Yalentia, I am not quite sure that it would even be necessary to put the skid on, so gentle are the ascents and descents upon that long route. From Valentia the road would lie down hill for about two hundred miles to the point at which the bottom is now covered by 1700 fathoms of sea-water. Then would come the central plain, more than a thousand miles wide, the inequalities of the surface of which would be hardly perceptible, though the depth of water upon it now varies from 10,000 to 15,000 feet; and there are places in which Mont Blanc might be sunk without showing its peak above water. Beyond this the ascent on the American side commences, and gradually leads, for about three hundred miles, to the Newfoundland shore." The central plain here described, which has been since found to extend many hundred miles north and south of the cable line, is covered almost everywhere by that soft mealy sort of mud of which we have already spoken : and this, it is now confidently believed, is nothing else than a stratum of Chalk Rock in an early stage of for- mation. When thoroughly dried it assumes a whitish colour, and exhibits a texture which even to the super- ficial observer appears closely to resemble fine chalk. Nay, we are told that, if so disposed, one may take a bit of it in his fingers and write with it upon a black-board. Like chalk, too, when chemically analysed it is found to be almost pure carbonate of lime. CHALK UNDER THK MICROSCOPE. 1 1 7 But there is a yet more striking analogy between the mud of the Atlantic and the White Chalk of Europe. Both have been submitted to the magnifying power of the Microscope ; and, after an examination conducted with scrupulous care, a wonderful and almost startling identity of mineral, or rather we should say of organic, composition has been established between them. To the naked eye Chalk is simply a soft, earthy sort of stone. But when a thin transparent slice is placed under the Microscope, the general mass is found to be made up of very minute particles, in which are imbedded a vast number of other bodies possessing a well-defined form and structure. These are of various sizes, but on a rough average may be said not to exceed a hundredth of an inch in diameter. Hundreds of thousands of them are sometimes contained in a cubic inch of Chalk, together with countless millions of the more minute granules. Professor Huxley succeeded in separating these bo- dies from the mass of granules in which they were imbedded, and by examining them apart, he has ascer- tained still more fully their exact structure and composi- tion. " Each one of them," he says, " is a beautifully constructed calcareous fabric, made up of a number of chambers communicating freely with one another. They are of various forms. One of the commonest is some- thing like a badly-grown raspberry, being formed of a number of nearly globular chambers of different sizes congregated together. It is called Globigerina ; and some specimens of Chalk consist of little else than Glo- bigerinse and granules." 1 1 8 REMARKABLE IDENTITY OF COMPOSITION Previous to 1857 the Globigerinse of the Chalk were a matter of no small controversy among Geologists and Naturalists. Some contended that they were the organic remains — the shells or skeletons — of ancient animalcules. Others were disposed to regard them simply as aggrega- tions of lime which, so to speak, chanced to assume the form of these little chambered bodies : though it was not easy to explain, on this hypothesis, how these chance concretions, however much they varied in size, preserved over the whole of Europe the same exact form and struc- ture. But the controversy is now at an end. The spe- cimens of the Atlantic ooze brought home by Captain Dayman, when examined under the higher powers of the Microscope, are found like Chalk to be composed almost entirely of Globigerinse. And that no doubt may remain as to their organic origin, a portion of the fleshy integument of the little animalcules is seen, in many cases, still adhering to the calcareous skeleton. " Globigerinse of every size," we are told, " from the smallest to the largest, are associated together in the Atlantic mud, and the chambers of many are filled by a soft animal matter. This soft substance is, in fact, the remains of the creature to which the Globigerina shell, or rather skeleton, owes its existence — and which is an animal of the simplest imaginable description. It is, in fact, a mere particle of living jeUy, without defined parts of any kind — without a mouth, nerves, muscles, or dis- tinct organs ; and only manifesting its vitality to ordinary observation by thrusting out and retracting, from all parts of its surface, long filamentous processes which serve BETWEEN CHALK ROCK AND ATLANTIC MUD. 1 19 for arms and legs. Yet this amorphous particle devoid of everything which in the higher animals we call or- gans, is capable of feeding, growing, and multiplying ; of separating from the ocean the small proportion of car- bonate of lime which is dissolved in sea-water ; and of building up that substance into a skeleton for itself, ac- cording to a pattern which can be imitated by no other known agency." That the same process is going on in other parts of the ocean appears by observations made by Sir Leopold M'Clintock during the cruise of the Bulldog in i860. He discovered that a calcareous ooze having the con- sistency of putty is spread out over extensive areas be- tween the Faroe Islands and Iceland, and also between Iceland and Greenland. Of this mud about ninety-five per cent is composed of Globigerinae, which in some in- stances were brought up actually living to the surface, and busily engaged in secreting, by their vital powers, carbonate of lime from the waters of the sea.' Professor Huxley goes yet one step further in follow- ing out the resemblance between the Chalk rock that exists in the Crust of the Earth and the stratum of Chalk that is now growing up in the depths of the Atlantic. Not only are the Globigerinae, of which the one is in great part composed, identical with the animalcules that makeup about nine-tenths of the other, but even the mi- nute granules that constitute the residue of each forma- tion, correspond in a very remarkable manner. " In working over the soundings collected by Captain Day- man, I was surprised to find that many of what I have ' Lyell, Elements of Geology, p. 318. 1 20 OKGANIC ORIGIN OF CHALK DEMONSTRATED. called the Granules of that mud, were not, as one might have been tempted to think at first, the mere powder and waste of Globigerinse, but they had a definite form and size. I termed these bodies Coccoliths, and doubt- ed their organic nature. Doctor Wallich verified my observation, and added the interesting discovery that, not unfrequently, bodies similar to these Coccoliths were aggregated together into spheroids, which he termed Coocospheres. So far as we knew, these bodies, the nature of which is extremely puzzling and problematical, were peculiar to the Atlantic soundings. " But a few years ago Mr. Sorby, in making a careful examination of the Chalk by means of thin sections and otherwise, observed, asEhrenberg had done before him, that much of its granular basis possesses a definite form. Comparing these formed particles with those in the At- lantic soundings he found the two to be identical ; and thus proved that the Chalk, like the soundings, contains these mysterious Coccoliths and Coccospheres. Here was a further and a most interesting confirmation, from internal evidence, of the essential identity of the Chalk with modern deep-sea mud." We may, therefore, set it down as certain, first, that the formation of Chalk Rock is going on very extensively at the present day ; and secondly, that the chief agency employed in its production is no other than the vital ac- tion of minute animalcules. This is no longer merely a plausible theory or an ingenious hypothesis : it is sim- ply a matter of fact ascertained by direct observation. If then it is just and philosophical to ascribe like effects to like causes, the conclusion is plain that the White COEAL EEEFS. 1 2 1 Chalk of Europe came into existence in some far distant age by just such a process as that which is now in ope- ration on the bed of the Atlantic Ocean. From the Chalk mud of the Atlantic we will now pass to the Coral Reefs that are growing up beneath the waters of thePacific and thelndian Oceans. Everyone has heard of Coral Reefs and Coral Islands : yet we fancy many per- sons have but vague and indefinite notions about them. We shall, therefore, in the first place, give a brief ac- count of their general appearance, their extent, and their geographical distribution. Afterwards we shall give some of the evidence which goes to show that these huge masses of rock owe their existence to the organic powers of minute living animalcules. The Coral Reef is familiar to the navigator of tropical seas under a great variety of forms, and in many diffe- rent stages of development. In one case it is a chain of hidden rocks rising not quite to the level of the sea ; in another it appears just above the waters, but is washed over by each returning tide ; while in another it rises up beyond the reach of the waves, is clothed with luxuriant vegetation, and inhabited by various species of animals, even by man himself. Again there is great diversity of outline among these rocks, whether they are sunk be- neath the surface of the waters, or lifted above them. But all may be reduced to four classes, of which we pro- pose to give a short description. First is the Atoll, or lagoon island. It is a circular strip of limestone rock enclosing a shallow lake within, and surrounded by a deep and often unfathomable ocean 122 GENERAL CHARACTER AND OUTWARD APPEARANCE without. The scene presented by some of these circular reefs is described hy travellers as equally striking for its singularity and its beauty. " A strip of land a few hun- dred yards wide is covered by lofty cocoa-nut trees, above which is the blue vault of heaven. This band of verdure is bounded by a beach of glittering white sand, the outer margin of which is encircled with a ring of snow-white breakers, beyond which are the dark heav- ing waters of the ocean. The inner beach encloses the still clear water of the lagoon, resting in its greater part on white sand, and, when illuminated by a vertical sun, of a most vivid green." These lagoon islands are often found in groups stretching, with little interruption, for many hundred miles across the ocean. The Maldives, for example, which lie a little distance to the south-west of Hindostan, form a continuous chain, running due north and south, four hundred and seventy miles in length and fifty miles in breadth. Each successive link in this chain does not consist, as might be supposed, of a single circular reef, but it is rather a ring of small coral islets, sometimes more than a hundred in number, each of which is itself a perfect Atoll or lagoon island such as we have just de- scribed. Of these miniature islets many are from three to five miles in diameter ; while the larger rings of which they form a part are from thirty to fifty. The Lac- cadive islands, a little more to the north exhibit a simi- lar arrangement, and indeed would seem to be a conti- nuation of the same group. In the Pacific are found some chains of coral islands yet more extensive ; as for OF CORAL REEFS. 123 instance the Dangerous Archipelago, which is upwards of eleven hundred miles in length, and from three to four hundred in breadth ; but the islands within these spaces are thinly scattered, and insignificant in size. Sometimes the annular strip of coral rock encloses within itself a lofty island, which rises up from the cen- tre of the lagoon. In this case it is called an Encircling Eeef; the lagoon being simply a broad channel sur- rounding the island in the centre, and encompassed itself by the coral rock. An example occurs in the is- land of Vanikoro, celebrated for the shipwreck of La Peyrouse, where the Encircling Keef runs at a distance of two or three miles from the shore, the channel be- tween it and the land having a general depth of between two and three hundred feet. The well-known moun- tainous island of Tahiti in the South Pacific Ocean is also encompassed by an Encircling Keef, from which it is separated by a broad belt of tranquil water. A third class of Coral Eeefs consists of those which run parallel to the shores of continents or great islands, from which they are cut off by a broad channel, to which the sea has free access through certain open pas- sages in the rock. They are called Barrier Reefs ; and differ from the former only in this, that they do not sur- round the land, but run parallel to it at a distance of some miles. The Great Barrier Eeef of Australia offers a noble example. It has been described as a huge, massive, submarine wall or terrace, fronting the north- eastern coast of that continent, varying from ten to ninety miles in breadth, and extending, with some trifling 1 24 DISTRIBUTION OF COBAL REEFS. interruptions, to a length of 12 jo miles. Another reef of the same kind, 400 miles in length, faces the western coast of the long narrow island of New Caledonia. When a chain of Coral rocks approaches close to the shore, so as to leave no intervening channel of deep water, they are called Fringing Keefs ; and these con- stitute the fourth and last class of the the Coral forma- tion. They prevail everywhere in tropical regions, and appear as banks of coral encrusting the rocky shores of islands and continents. As regards the geographical distribution of Coral Reefs, the first circumstance that claims our notice, is that they are exclusively confined to the warmer regions of the globe. They exist in great profusion within the tropics, and are rarely to be found beyond the thirtieth parallels of latitude on each side of the Equator. The only remarkable exception is in the case of the Bermuda Islands in 32° north latitude; but here, it is to be ob- served, the ocean is warmed by the waters of the Gulf Stream. Another singular fact is the almost total ab- sence of Coral Reefs from the Atlantic Ocean. In fact, the Bermudas, we believe, constitute here again the only exception. The Pacific, on the contrary, is won- derfully productive of coral ; also the Indian Ocean, the Persian and Arabian Gulfs, and the Red Sea. It may gratify, perhaps, the curiosity of some readers, if we add a word on the Red Coral which is now so fa- vourite an ornament in the fashionable world. Though it never attains to the magnitude of those reefs and is- lands we have been describing, it partakes neverjtheless of ORIGIN OF CORAL REEFS. 125 the same peculiar structure ; and no doubt is entertained that, like them, it derives its existence from animal life, in the manner we shall presently explain. It is produced chiefly in the Mediterranean, in the Red Sea, and in the Persian Gulf; and is brought up from great depths by means of a grappling apparatus attached to boats. The largest pieces have a shrub-like branching form, and are supposed to grow to the height of one foot in about eight years.' So much for the existence of the Coral Formation. Next comes the question of its origin, with which, of course, we are chiefly concerned. It is now the received belief of all distinguished Naturalists, that these huge and wide-spread masses of limestone rock, against which the breakers of the ocean are ever thundering in vain, are the work of tiny marine animalcules, and chiefly of those seemingly insignificant creatures known by the name of Polyps or Zoophytes. The Zoophyte, they tell us, is a mason who himself produces the stones that he employs in his building. " He has neither plane, nor chisel, nor trowel ; there is no sound of hammer in his city. He erects mighty and enduring edifices, yet has no mechanical power by which to raise his rocks to their summits. He can answer thee nothing — no tongue, no eyes, no hands, no brains, has he — yet from the caves of old ocean has he raised that which fills you with admiration." Surely, if all this be true, these countless 1 Lyell, Principles of Geology, vol. ii. chap. xlix. ; Mantell, Wondera of Geology, Lecture vi. ; Jukes, Manual of Geology, pp. 130-3. 2 Sacred Philosophy of the Seasons, by the Eev. Henry Duncan, D. D. ; Summer, p. 168. 1 26 THE POLYP ANIMAL AND THK POLYP EDIFICE. myriads of animalcules call aloud to us from the depths of the ocean in language that cannot be mistaken : " Know ye that the Lord He is God ; it is He that hath made us, and not we ourselves."' The Zoophyte belongs to the simplest form of the ani- mal creation. Its body consists merely of a pouch or sto- mach, with tentacles arranged round the margin, which it can extend at pleasure to supply itself with food. In many species the individuals grow together on a com- mon stem, from which new members are constantly shooting forth like buds from the branches of a tree. Hence the origin of the name Zoophyte, which literally means a plant-like animal. The common stem on which they grow is sometimes composed of a horny substance, but more generally it is pure carbonate of lime, which they secrete by the powers of organic action from the waters of the sea. It forms, therefore, a kind of internal skeleton or framework, to which the soft, ge- latinous parts of the animal adhere, pretty much as, in the case of other animals, the flesh adheres to the bones. Thus we have, as it were, a community of liv- ing creatures, growing together upon one common stony framework, called a Polypidom or Polyp edifice, which they themselves build by the very fact of living. The peculiar structure of these wonderful little com- munities may perhaps be made more intelligible by the aid of a few illustrations. Figure 4 exhibits the branch- ing skeleton and, at the extremities of the branches, the several Polyps by whose vital action the skeleton has ' Ps. xcix. 3. EXAMPLES OF THE LIVING ZOOPHYTE. 127 been constructed. Some of the animalcules are shown in a state of activity with their tiny arms spread out in search of food : others are withdrawn within their cells, and appear in a state of repose. This species of Zoo- Fig. 4. Fig. S. Campanularia Gelatinosa. Gorgonia Patula. phyte, which is highly magnified in the figure, flourishes abundantly on the shores of Ireland and England. It has received the name of Campanularia, from the bell- like form of its cells. Our next cut represents a Gorgo- nia from the Mediterranean, which is also considerably magnified. The fleshy integument of this specimen is of a brilliant red colour : the Polyps are arranged in rows on each side of the stem, and are shown in a state of ex- pansion. A mass of Coral animalcules, which are known by the name of Frustra Pilosa, is represented of the natural size in Figure 6. To the naked eye it seems hke a piece of 128 EXAMPLES OF THE LIVING ZOOPHYTE. fine net- work, disposed around a fragment of sea- weed, which may be observed protruding in the upper part of our illustration. With the aid of an ordinary magnifier Fig. 6. Frustra Pilosa. Madrepora Plantaginea. the net-like surface is seen to abound in minute pores arranged with much regularity. Each of these pores is the cell of a Zoophyte. And if a fragment of Flustra be examined with a powerful microscope, when immersed in sea- water, the curious little inhabitants themselves may be seen darting in and out of their cells, expanding and contracting their long feelers, and exhibiting altogether a wonderful activity. In the adjoining woodcut, Figure 7, is shown another interesting species of the arborescent Zoophyte. It belongs to the family of Madrepores, and abounds in almost all Coral Reefs. Alive under water it appears clothed in a gelatinous coating of rich and va- ried hues. But when removed from its native element RED AND PINK CORAL. 1 29 this gelatinous coating, which is the living animal sub- stance, quickly melts away ; and, in some instances, runs off from the calcareous skeleton in a kind of watery slime. A good idea of the celebrated red and pink Coral of commerce, so much admired for its brilliant colour, and the high polish of which it is susceptible, may be ga- thered from our next illustration. As in the other spe- Fig. 8. CoraUium Eubrum. cies to which we have referred, the calcareous skeleton is enveloped in a living gelatinous substance, from which the Zoophytes seem to shoot out like buds from the bark of a tree. Several of these animalcules are exhibited in our figure, in the active enjoyment of life ; gathering in, with their expanded tentacles, the elements of their stony edifice from the surrounding waters. After death the 'K 130 THE COKAL ANIMAL IN TROPICAL SEAS. fleshy integument is wasted away by the action of the sea : and the framework that remains behind, washed ashore by the waves, or hooked up by the Coral fisher- man, is wrought into brooches, bracelets, necklaces, and other ornaments of various kinds. Not a few varieties of the Coral-producing Zoophytes are to be found in actual living reality on our own coasts, where the curious student may examine for himself their habits and general structure. But it is in the warmer regions of the Earth that they are developed in the greatest numbers, and decked in the brightest hues. Those who have seen them through the crystal waters of tropical seas, swarming in countless multitudes on the clear white sand below, speak with enthusiasm of their luxuriant profusion and of their striking beauty. Com- bining to a picturesque elegance of form a rich variety and pleasing harmony of colours, they present to the eye a scene which has been compared to a magnificent garden, laid out in diverse beds of rare and splendid flowers. So far we have spoken only of the Polypidom, that is to say, the community of Polyps living together on a common stem of their own construction. Now this Po- lypidom is the first element of the Coral Reef. In some species of Zoophytes, the Eed Coral for instance, the calcareous stem never attains a size greater than that of a diminutive shrub. But in others, and they are very numerous, especially in tropical seas, there seems to be no limit to the growth of the solid stony framework. As the existing generation of Zoophytes is dying out new GROWTH OF CORAL REEFS. I 3 1 individuals are ever budding forth, -which continue un- ceasingly to secrete carbonate of lime, as their prede- cessors had done before them, from the waters of- the ocean ; and thus the tree-like form spreads its branching arms on every side, growing upwards and outwards day by day. The soft gelatinous parts of those generations that have passed away are, in a short time, dissolved, and the stony skeleton alone remains behind. Ages roll on : the calcareous framework, ever increasing in size, becomes at length a formidable rock ; and this rock is the Coral Eeef. Let it not be supposed we are here advancing a theory : we are only stating a fact that has been established by close and repeated observations. All the phenomena exhibited in the development of the Polypidom, are ex- hibited no less plainly in every Coral Eeef that has yet been examined. On the surface of the Reef are the living Zoophytes, clinging to the calcareous skeleton which is ever growing larger through the unconscious action of their vital functions ; while immediately be- neath may be seen the same stony skeleton, already di- vested of its fleshy integument, and beginning to assume the appearance of compact and massive rock. We can behold, therefore, the mason at work on the upper story of his building, and the structure already finished below. And so we have little less than ocular demonstration that the Coral Keef is the work of the Zoophyte. It must not be supposed, however, that in every part of the Coral Eeef, the form and outline of the stony skeleton are exactly preserved. Fragments of the rock K 2 132 THE SUNKEN REEF CONVERTED are broken oflF by tbe force of the waves, and mixed up with the comminuted shells of oysters, mussels, and other crustaceous animals inhabiting the same waters. In this way a sort of calcareous gravel, sometimes a calcareous paste, is formed, which fills up the interstices, and con- nects the tree-like coral into a compact rock. We have yet to explain how the Coral Reefs come, in many cases, to rise above the surface of the ocean, and to form dry land : for it has been found that the reef-building Zoophytes require to be continually im- mersed in salt water, and therefore, by their own efforts, they cannot raise their structure above the ordinary level of the sea. This question was for a long time involved in obscurity ; but it has been cleared up by the actual observations of Naturalists in modern times. The fol- lowing description, which is given to us by Chamisso, the companion of Kotzebue on his voyages, will convey a good idea of the process by which a sunken reef is often converted into a smiling, fruitful island. " When the reef is of such a height that it remains almost dry at low water, the corals leave off building. Above this line a continuous mass of solid stone is seen composed of the shells of moUusks and echini, with their broken- off prickles and fragments of coral, united by calcareous sand, produced by the pulverization of shells. The heat of the sun often penetrates the mass of stone when it is dry, so that it splits in many places, and the force of the waves is thereby enabled to separate and lift blocks of coral, frequently six feet long and three or four in thickness, and throw them upon the reef, by which INTO A FRUITFUL ISLAND. 1 3 3 means the ridge becomes at length so high that it is covered only during some seasons of the year by spring tides. After this the calcareous sand lies undisturbed, and offers to the seeds of trees and plants cast upon it by the waves, a soil upon which they rapidly grow, to overshadow its dazzling white surface. Entire trunks of trees, which are carried by the rivers from other countries and islands, find here at length a resting place after their long wanderings : with these come some small animals, such as insects and lizards, as the first inhabi- tants. Even before the trees form a wood, the sea-birds nestle here ; stray land-birds take refuge in the bushes ; and, at a much later period, when the work has been long since completed, man appears and builds his hut on the fruitful soil."' Another question that seems to call for some explana- tion is suggested by the well known habits of the Zoo- phytes themselves. From the observations of Kotzebue and Darwin it appears that those species which are most effective in the construction of Eeefs cannot flourish at a greater depth than twenty or thirty fathoms ; whereas the coral rocks rise up in many cases from the bottom of an unfathomable ocean. How, then, it may be asked, have the foundations of these wonderful structures been laid ? This question opens a wide field for philosophical speculation ; and we freely admit that no theory of Coral Eeefs can be regarded as complete and satisfactory, which does not furnish a reasonable answer. But so far 1 Kotzebue's Voyages, 1815-18, vol. iii., pp. 331-33- 134 ME. DARWIN'S HYPOTHESIS OF SUBSIDENCE. as the purpose of our argument is concerned, it is quite sufficient if a stratum of solid limestone twenty fathoms thick has been formed mainly through the agency of these minute animalcules. And this conclusion, so abundantly demonstrated by facts, is left quite untouched by the difficulty to which we now refer. It will be interesting, however, to notice in passing the explanation of this phenomenon first suggested by Mr. Darwin, and now very generally accepted. He maintains that the whole Coral Keef — foundations and superstructure alike — ^is, in most cases, the result en- tirely of organic agency. The reef-building Zoophyte always begins his labours in water that is comparatively shallow. But as he is building upwards it often hap- pens that the bed of the sea is sinking downwards in pretty nearly the same proportion : and thus the reef is ever increasing in height from its original base, while the living mass of Zoophytes on its upper surface re- mains in about the same depth of water as when the building first began. This theory is supported by a vast amount of curious and ingenious reasoning. In the first place, there is nothing more remarkable in the physical conformation of the Globe, than the immense predominance of water over land throughout those extensive tracts of ocean where Coral Eeefs abound. Now this is just what we should naturally expect if the hypothesis of Mr. Darwin were admitted : for wherever the Crust of the Earth has been subsiding for many ages on a large scale, the do- main of the sea must of necessity have been considerably ME. DAEWIN'S hypothesis OF SUBSIDENCE. 1 3 5 enlarged, and that of the land contracted in proportion. Again, this hypothesis will be found to harmonize most perfectly with all the phenomena' of Fringing Eeefs, Barrier Keefs, Encircling Eeefs, and Lagoon Islands. The Fringing Reef represents as it were the first stage of progress. The building operations have just com- menced near the shore of some island or continent, and but little space intervenes between the land and the in- crusting wall of coral. Then, as the Crust of the Earth gradually subsides, the water encroaches on the land, and forms a channel between it and the reef. Meanwhile the Zoophytes are at work, and the coral rock is grow- ing upwards as the foundation on which it rests is sink- ing downwards : each year it is higher from the bed of the sea, and yet no nearer to the surface of the waters. And when at length the channel, which is ever growing wider and wider, has reached a certain limit, the Fringing Keef becomes a Barrier Reef, or if it encompasses an island, an Encircling Reef. Lastly the Encircling Reef will finally become a Lagoon Island, when the highest peaks of the land it encloses have slowly disappeared beneath the surface of the waters. In confirmation of this reasoning Mr. Darwin has pointed out numerous examples to illustrate each inter- mediate stage through which, according to his hypo- thesis, the Coral Reef must pass in the progress of its construction. He traces a gradual transition from the low bank of coral incrusting a rocky shore to the En- circling Reef that compasses round a lofty island, like Tahiti, with a broad channel between. Then he shows 136 CORAL BOOKS IN THE CRUST OF THE EARTH. how this channel insensibly becomes wider and wider, encroaching more and more upon the land, until at length only a few high peaks remain above water. Finally he leads us on to the case of a perfect Atoll, within which no trace of land remains to be seen ; and the channel, now become a lagoon, is encompassed by a Keef of Coral Kock that rises steeply from an unfathomed ocean. > We do not mean to dwell upon this ingenious specu- lation, which would carry us too far from the object at which we are aiming. It seems to us, however, that the arguments in its favour are at least deserving of careful consideration : and we may add that they receive new strength from the facts we shall have occasion hereafter to bring forward, when we come to speak of the undu- lating movements to which the Crust of the Earth has been subject at many different times, and in many dif- ferent localities, even within the historic period. The formation and structure of existing Coral Keefs being once fairly established. Geologists have little dif- ficulty in ascribing a similar origin to many of the lime- stone strata that are found in the Crust of the Earth. For though the internal texture has been considerably modified in the long course of ages, by chemical and other influences, nevertheless the stony skeletons of the reef-building Zoophytes can be distinctly recognized in great abundance. Indeed it is not an uncommon thing to meet with limestone rock exhibiting plainly to the eye all the appearance of Coral Reefs lifted up from the bed of the ocean. " The Oolite," says Doctor Mantell, CORAL ROCKS IN THE CRUST OF THE EARTH. 137 " abounds in corals, and contains beds of limestone which are merely coral reefs that have undergone no change but that of elevation from the bottom of the deep, and the consolidation of their materials. The Coral-rag of Wilts presents in fact all the characters of modern reefs : the polypifera belong chiefly to the Astrseidee, the genera of which family principally contribute to the formations now going on in the Pacific. Shells, echinoderms, teeth, and bones of fishes, and other marine exuviae, occupy the interstices between the corals, and the whole is con- solidated by sand and gravel, held together in some in- stances by calcareous, in others by siliceous infiltrations. Those who have visited districts where the Coral-rag forms the immediate subsoil, and is exposed to view in the quarries or in natural sections, must have been struck with the resemblance of these rocks to modern coral banks."' Even in many of our finest marbles the coral skeletons may be traced distinctly enough, and contribute not a little to that variegated colour which is so much ad- mired. Nay it is recorded by Mr. Parkinson that he discovered in a piece of sold marble, the animal inem- brane itself by which the lime was originally abstracted from the sea. He immersed the marble in dilute mu- riatic acid ; and he relates with delight how, as the calcareous earth dissolved, and the carbonic acid gas escaped, he observed the animal tissue begin distinctly to appear in the form of light elastic membranes.' ' Wonders of Geology, p. 648. » Organic Eemains of a Former 'World, Tol. ii. p. 16. CHAPTER IX. STRATIFIED ROCKS OF ORGANIC ORIGIN — ILLUSTRATIONS FROM VEGETABLE LIFE. OKIGIN OP COAL — EVIDENT TKAOES OF PLANTS ANB TBEES IN COAL- MINES — COAL MADE UP OP THE SAME ELEMENTS AS WOOD — BEDS OP COAL POUND KESTINO UPON CLAT IN WHICH ARE PRESERVED THE ROOTS OP TREES — INSENSIBLE TRANSITION FROM WOOD TO COAL POREST-OOVERED SWAMPS — ACCUMULATIONS OF DRLFI WOOD IN LAKES AND ESTUARIES — PEAT BOGS — BEDS OP LIGNITE— SEAMS OP Pt'RE COAL WITH HALF CARBONIZED TREES, SOME LYING PROSTRATE, SOME STANDING ERECT — SUMMARY OF THE ARGUMENT HITHERTO PURSUED — OBJECTION TO THIS ARGUMENT PROM THE OMNIPOTENCE OP GOD — ANSWER TO THE OBJECTION. As animals by organic action extract lime from the waters of the ocean they inhabit, which being converted in the first instance into minute shells, or stony skele- tons, afterwards passes into a compact and solid rock, so in like manner do plants and trees extract carbon from the atmosphere in which they vegetate, and convert it into coal. No reasonable doubt can now be entertained, that coal derives its existence, almost entirely, from the woody tissue of sunken swamps and forests. Though the nature of the process by which this transformation takes place, is yet but imperfectly understood, and is, indeed, at the present momenta subject of much discus- sion and controversy, nevertheless the fact that the change has taken place is fully accepted by all as an established truth, and is supported by an accumulation of evidence which it is not easy to resist. IMPRESSIONS OF PLANTS AND TREES IN COAL. 1 39 The first circumstance to which we shall call attention, is the wonderful profusion of vegetable life that is always associated with coal. Every one who has descended at any time into a coal mine, or who has examined the spe- cimens usually exhibited in a well furnished museum, must have been struck by the countless forms of trees and plants, which still remain vividly impressed on this black and unsightly mineral. Dr. Buckland has described this phenomenon with much vigour and beauty in his ce- lebrated Bridgewater Treatise : " The finest example I have ever witnessed is that of the coal mines of Bohemia just mentioned. The most elaborate imitations of living foliage upon the painted ceilings of Italian palaces, bear no comparison with the beauteous profusion of extinct vegetable forms with which the galleries of these instruc- tive coal mines are overhung. The roof is covered as with a canopy of gorgeous tapestry, enriched with fes- toons of most graceful foliage, flung in wild irregular profusion over every portion of its surface. The effect is heightened by the contrast of the coal-black colour of these vegetables with the light ground-work of the rock to which they are attached. The spectator feels him- self transported, as if by enchantment, into the forests of another world ; he beholds trees of forms and characters now unknown upon the surface of the earth, presented to his senses almost in the beauty and vigour of their primeval life ; their scaly stems and bending branches, with their delicate apparatus of foliage, are all spread forth before him, little impaired by the lapse of countless ages, and bearing faithful records of extinct systems of CHEMICAL COMPOSITION OF WOOD AND COAL. 141 vegetation, which began and terminated in times of which these relics are the infallible historians." The next important fact that points to the vegetable origin of Coal is, that wood and Coal are both composed of the same ultimate elements — carbon, hydrogen, and oxygen. This analogy is the more remarkable when we are told that no other rock except Coal exhibits anything approaching to this composition. It is true that the elements just enumerated do not exist in the same pro- portions in wood and in Coal. But the difference, when rightly understood, rather tends to confirm our theory that the one is derived from the other. There is more carbon in Coal than in wood ; while there is less oxygen and less hydrogen. To explain how this may have come to pass during the process of transition, we must call in the assistance of the chemist. It appears from the re- searches of Liebig that, when vegetable matter is buried in the earth, exposed to moisture, and partially or en- tirely excluded from the air, the process of decomposi- tion sets in, and that under this process carbonic acid gas and carburetted hydrogen gas are slowly evolved. At the same time a portion of the oxygen when set free would naturally enter into a new combination with a portion of the hydrogen, and form water. The result of these several changes would necessarily be, that the accumulation of vegetable matter buried in the earth would part, in course of time, with no small share of its carbon, its hydrogen, and its oxygen, but not with all in the same proportions : for the new combinations would use up more of the oxygen than of the hydrogen, and 142 CHOKE-DAMP AND FIRE-DAMP. more of the hydrogen than of the carbon.' In other words, if the process should have gone on for a sufl&cient lapse of ages, these elements would no longer exist to- gether in the proportions which are necessary to consti- tute wood, but would rather exist in the proportions which are found to constitute coal.* This explanation is confirmed by a fact with which our readers are no doubt familiar. According to the expla- nation, carbonic acid and carburetted hydrogen are evolved during the process by which coal is produced from wood. We should therefore expect to find these gases closely associated with Coal. If they are not so associated, their absence is a serious objection against our theory ; but if they are so associated, their presence is a strong evidence in its favour. Now on this point, as every one knows, practical miners bear testimony that the fact corresponds exactly with our theory. They tell us that reservoirs of Choke-damp, which is carbonic acid, and of Fire-damp, which is carburetted hydrogen, are found very commonly pent up in the crevices and cavities of coal beds, and are the cause, when tapped, of many of the accidents which take place. They even assure us that ' Carbonic acid gas contains two equivalents of oxygen to one of car- bon, the chemical expression for the compound being COa ; carburetted hydrogen, vhich is the gas we employ in illuminating our streets and houses, contains four equivalents of hydrogen to two of carbon, and is chemically expressed by the symbols C2H1 ; water is composed of one equivalent of oxygen, and one of hydrogen, the symbolic form being HO. 2 See Jukes, Manual of Geology, pp. 138-141. Lyell, Elements of Geology, p. 500. ALTERNATE BEDS OF COAL AND CLAY. 143 some beds of coal are so saturated with gas that, when cut into, it may be heard oozing from every pore of the rock, and the coal is called singing coal by the colliers.' To sum up, then, what we have said on this point : it appears, first, that the same constituent elements are found in wood and Coal ; secondly, though they do not exist in the same proportions in the two substances, the difference is fully accounted for by the changes which we should naturally expect to take place when large ac- cumulations of vegetable matter are buried in the earth ; thirdly, in the hypothesis of these changes, carbonic acid and carburetted hydrogen would certainly be developed ; and in point of fact, these gases are found intimately associated with Coal all over the world. There is another remarkable fact which fits in most admirably with our theory. Coal is found at the present day in the Crust of the Earth, disposed in thin seams or beds, and each bed is almost uniformly found to rest upon a stratum of fine clay sometimes several feet in thickness. This is just what our theory would lead us to expect. If coal is produced from plants and trees, these plants and trees must have grown upon some suitable soil; and, therefore, in this hypothesis we should expect, ordinarily speaking at least, to find abed of clay beneath every bed of Coal. But this is not all. When we examine more closely the stratum on which the Coal reposes, we find the roots and stems of trees mingled with the clay in the greatest profusion. In the ' Jukes, Manual of Geology, p. 140- 1 44 PRACTICAL ARGUMENT. Welsh coal field, in a depth of twelve thousand feet, there are from fifty to a hundred beds of Coal, each lying on a stratum of clay abounding in these remains.' We now come to an argument of a practical kind which appeals to common sense and common experience. Let us suppose that a person wholly unacquainted with the art of manufacturing paper, were to enter a paper mill when the work-men are away, and the process of manu- facture for a time suspended. At first sight he would probably find it difficult to persuade himself, that the piles of clean white paper, which attract his notice at one end of the building, are produced from the heaps of filthy rags which he sees accumulated at the other. But if he be a sagacious observer, he will soon find evidence to convince him that this is really the case. For he will perceive, upon close examination, that the self-same ma- terial is exhibited in every intermediate state of progress from one extreme to the other. First, there is the great chest with its numerous compartments, in which the rags are seen carefully sorted, according to their various de- grees of quality and texture. Next comes the fulling mill where they are washed and bleached. Then the revolving cylinder, furnished on the exterior surface with sharp blades or cutters ; and the vat in which it moves is filled with the rags, which now assume the form of a tlyn liquid pulp. Advancing still further he will see this pulp evenly spread out upon a wire-gauze frame, 'See ManteU, 'Woiiders of Geology, pp. 680-2; also 760 ; Lyell, Elements of Geology, 464, 465. GRADUAL TEANSITION FROM WOOD TO COAL. 145 and now at last it is beginning to exhibit some likeness to the form and substance of paper. Further on it is seen pressed and dried ; and last of all cut into sheets and laid aside in lofty piles. Now it seems to us that we are placed in somewhat of the same position, as regards the manufacture of Coal, We cannot observe the process actually going on : for though, in this process, the work is never suspended, the workmen never at rest, yet extending as it does over a space of many centuries, it is too slow to be sensible ; and besides it is conducted in great part beneath the sur- face of the Earth. Nevertheless we can trace the pro- gress of change through each intermediate stage of the transition, from one extreme to the other, — from the primeval swamps and forests through the numerous varieties of Peat and Lignite to the richest beds of pure Coal. First, then, we have the great forest-covered swamps, like those which now occupy the valley and delta of the Mississippi. They are composed in many cases of pure vegetable matter without any intermixture of earthy sedi- ment. A dense growth of reeds, and shrubs, and herb- age of every kind, covers the whole surface of the land, mixed up with the decaying leaves and prostrate trunks of forest trees. Sir Charles Lyell mentions a very re- markable fact observed in the swamps of Louisiana. During an unusually hot season, when any part of a swamp is dried up, if the surface be set on fire, a pit is burned into the ground many feet deep, in fact as far down as the fire can descend without meeting water; L 146 ACCUMULATIONS OF DRIFT-WOOD. and it is then found that scarcely any residuum or earthy matter is left.' Vegetable strata of this kind are produced, not only upon dry land by the growth and decay of forests, but also beneath the waters of lakes and estuaries, by the ac- cumulation of Drift-timber borne along in the current of swollen rivers. The Mackenzie River, which drains a great part of North-western America, affords many ad- mirable illustrations. Flowing as it does from south to north, it is subject to annual inundations when the snows begin to melt in the higher parts of its course, while the channel lower down, situated in colder latitudes, is still blocked up with ice. At this season then it over- flows its banks, and, sweeping through vast forests, car- ries away thousands of uprooted trees in its impetuous torrent. "As the trees," says Dr. Richardson, "retain their roots, which are often loaded with earth and stones, they readily sink, especially when water-soaked ; and accumu- lating in the eddies, form shoals, which ultimately aug- ment into islands. A thicket of small willows covers the new-formed island as soon as it appears above water, and their fibrous roots serve to bind the whole firmly, toge- ther. Sections of these islands are annually made by the river; and it is interesting to study the diversities of appearances they present according to their different ages. The trunks of the trees gradually decay until they are converted into a blackish-brown substance resem- bling peat, but still retaining more or less of the fibrous ' Elements of Geology, p. 488. ACCUMULATIONS OF DRIFT- WOOD. 147 structure of the wood ; and layers of this often alternate with layers of clay and sand, the whole being pene- trated, to a depth of four or five yards or more, by the long fibrous roots of the willows. A deposition of this kind, with the aid of a little infiltration of bituminous matter, would produce an excellent imitation of Coal, with vegetable impressions of the willow roots. " It was in the rivers only that we could observe sec- tions of these deposits ; but the same operation goes on, on a much more magnificent scale, in the lakes. A shoal of many miles in extent is formed on the south side of Athabasca Lake by the Drift-timber and vegetable de- bris brought down by the Elk River ; and the Slave Lake itself must in process of time be filled up by the matters daily conveyed into it from Slave River. Vast quanti- ties of Drift-timber are buried under the sand at the mouth of the river, and enormous piles of it are accumu- lated on the shores of every part of the lake." Not unfrequently it happens that these strata of vege- table matter, with the roots and trunks of trees, their branches, fruits, and leaves, more or less perfectly pre- served, are covered over by subsequent deposits. Such accumulations, we are assured by Doctor Mantell, have been found deep in the soil on the coast of England, in places that are still subject to periodical inundations. " The trees are chiefly of the oak, hazel, fir, birch, yew, willow, and ash ; in short, almost every kind that is in- digenous to this island occasionally occurs. The trunks and branches are dyed throughout of a deep ebony colour by iron ; and the wood is firm and heavy, and occasion- L 2 148 PEAT BOGS OP IRELAND. ally fit for domestic use ; in Yorkshire and elsewhere, timber of this kind is sometimes employed in the con- struction of houses."' Here, then, is the first stage of the conversion of wood into Coal, — a stratum more or less compacted together of vegetable matter, spread out sometimes over the surface of the dry land, sometimes on the floor of lakes and estuaries, and often buried be- neath an accumulation of subsequent deposits. The next stage in the process of transformation may be represented by those Peat Bogs which constitute one of the most remarkable physical characteristics of Ire- land, covering as they do an area equal to one-tenth of the whole island. In these the vegetable matter is more closely condensed, but the structure of the plants from which the Peat is derived is still preserved, and may be distinctly recognized by the naked eye. Nay we have still the prostrate trunks of trees lying around on every side as they fell to the ground in their ancient forests. The researches recently pursued upon this subject have brought to light a fact which is very much to our pre- sent purpose ; for it seems to prove our thesis by direct evidence. " In Limerick in the district of Maine, one of the states of North America, there are Peat Bogs of considerable extent, in which a substance exactly similar to cannel coal is found at the depth of three or four feet from the surface amidst the remains of rotten logs of wood and beaver sticks : the peat is twenty feet thick, and rests upon white sand. This coal was discovered on ' ManteU, Wonders of Geology, p. 67. TRANSITION FROM PEAT TO LIGNITE. 149 digging a ditch to drain a portion of the bog, for the purpose of obtaining peat for manure. The substance is a true bituminous coal, containing more bitumen than is found in any other variety. Polished sections of the com- pact masses exhibit the peculiar structure of coniferous trees, and prove that the coal was derived from a species allied to the American fir."' A similar phenomenon was observed by Doctor Dieffenbach in the Chathain Islands. In the same bed of peat he was able distinctly to trace a gradual transition from pure vegetable matter to a mi- neral substantially identical with common coal.^ But though Peat may thus, as it should seem, pass di- rectly into pure Coal, there are many cases in which it first assumes a more imperfect form, known under the name of Lignite. This substance is described as of a brownish colour, " soft and mellow in consistence when freshly quarried, but becoming brittle by exposure, the fracture following the direction of the fibre of the wood."' It clearly occupies an intermediate position between Peat and Coal. Like the former it still exhibits the stems and woody fibre of the plants from which it is derived, very little altered in their structure ; while on the other hand it is already beginning to acquire some of the con- sistency and density of Coal ; to which also it approaches much more closely in its chemical composition. It should be remembered, moreover, that Lignite does not designate a substance of a fixed invariable character. 1 Mantell, Wonders of Geology, p. 66. 2 Id. ib. ' Chemical Technology, Eonalds and Eiohardson, yol. i. p. 32. 150 TRANSITION FROM LIGNITE TO COAL. On the contrary, under the one general name are com- prised a definite number of varieties, leading from one extreme to the other by a series of almost insensible gradations ; the extreme variety on one side being scarcely distinguishable from Peat, while the extreme variety on the other is practically identical with ordinary Coal. It can hardly be doubted, therefore, that Coal must have the same origin as Lignite, while it is at least equally certain that Lignite has been derived from Peat ; and we have already seen what overwhelming evidence may be adduced to show that the origin of Peat is to be sought for in the sunken swamps and forests of a long past age. Lastly, when we come to examine the texture of Coal itself, we find much to confirm the conclusion at which we have thus arrived. In beds of pure Coal the remains of many species of plants have been detected, and some- times in such abundance as to constitute visiblythe bulkof the Coal. Even large trees are sometimes found standing erect in the Coal fields with their bark actually converted into this mineral. The annexed Figure represents a portion of the stem together with the roots of a tall fo- rest tree, Sigillaria, discovered not long ago in a Coal mine at Saint Helens, near Liverpool. The stem, which was nine feet high, was found erect in the seam of Coal, while the roots, ten in number, stretched away into the vegetable soil beneath. Not less than thirty such trees, some of them four or five feet in diameter, and all incrusted with Coal, were laid bare, a short time since, in a Colliery near New- TREES STANDING ERECT IN COAL. 151 castle, within an area of fifty yards square. " In 1830," writes Sir Charles Lyell, " a slanting trunk was exposed Fig. II. Stem and roots of a Forest Tree, Sigillaria. From a Coalmine, near Liverpool. a. The trunk traversing a bed of Coal. *. The roots spreading out in the underolay. in Cragleith quarry near Edinburgh, the total length of which exceeded sixty feet. Its diameter at the top was about seven inches, and near the base, it measured five feet in its greater, and two feet in its lesser, width. The bark was converted into a thin coating of the purest and finest Coal." Again, " in South Staffordshire, a seam of Coal was laid bare in the year 1844, in what is called an open work at Parkfield Colhery, near Wolverhampton. In the space of about a quarter of an acre, the stumps of I $2 FOREST TREES CONVERTED INTO COAL. no less than seventy-three trees with their roots at- tached, appeared, some of them more than eight feet in circumference. The trunks, broken off close to the root, were lying prostrate in every direction, often crossing each other. One of them measured fifteen, another, thirty 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 ten inches thick, which rested on a layer of clay two inches thick, below which was a second forest resting on a two-foot seam of Coal. Five feet below this again was a third forest, with large stumps of Lepidodendra, Oalamites, and other trees."' We have now brought to a close a very important line of argument in the Science of Geology. We have pointed out that, in the strata which compose the Crust of the Earth, there are rocks of various kinds, distin- guished from one another as well by the nature of the materials which compose them, as by the manner in which these materials are arranged together : and we have shown that rocks presenting the same general ap- pearances, and composed of exactly the same materials, are being produced in the present age upon the Surface of the Earth, through the agency of natural causes. Moreover, we have closely examined, in certain cases, the nature of the process by which the formation of these ' See Lyell, Elements of Geology, 477-81 ; Jukes, Manual of Geology, 138, 149-53; The EngUsh Gyclopsedia, Natural History Department, Article, Coal; Mantell, Fossils of the British Museum, Chapter I., Part I. PREJUDICE AGAINST GEOLOGICAL REASONING. 153 rooks is accomplished at the present day ; and we have seen how difficult it is, when the facts of the case are once clearly before us, to resist the conclusion that the rocks which we now find buried in the Earth, were produced in some former age, by the same causes which are stiU at work. We shall next proceed to inquire how far this conclusion is confirmed by the independent evi- dence of Fossil Remains. But before entering on a new line of argument, it is fit we should take notice of an objection which has sometimes been urged against the reasoning we have hitherto pursued, and which has done much to create and to keep alive a prejudice unfavourable to the Science of Geology. Religious writers have not un- frequently insinuated, and sometimes have plainly as- serted, that, in ascribing the present structure of the Earth's Crust to the operation of natural causes, Geolo- gists would seem to make no account of God's Omnipo- tence. A moment's reflection will convince the reader that this charge is utterly unphilosophical. Is it not plain that the more fully we appreciate and acknow- ledge the wonderful works of Nature, the more deeply must we become impressed with the power and wisdom of Him who is the Author and the Ruler of Nature ? To say that secondary causes exist, and to point out the monuments that bear witness to their operation in long -passed ages, is not to deny, but rather to affirm, the existence of a Great First Cause, upon whom they all depend for their existence, their preservation, and their guidance 1 54 OMNIPOTENCE OF GOD NOT IGNORED, We are everywhere reminded by abundant evidence, that it has pleased the Great Creator to employ the agency of His creatures in the fashioning and the adorn- ing of this material universe. He does not create at once, as He well might do, the great oak of the forest ; but He allows the seed to sink into the earth, where it is watered by the gentle dews of Heaven, and fructified by the genial warmth of the sun ; soon it puts forth a tender germ ; the germ in time, imbibing the ele- ments of its support from the air and the earth, be- comes a sapling, and the sapling a tree, which spreads its huge branches on every side, and serves for many purposes of ornament and of use. Or let us take the case of the honeycomb, that most curious and ingenious work, at once the palace and the storehouse of a vast and busy community. It is not produced in a moment by a simple act of creation. God has not made it Himself, but He has taught the bee to make it. In like manner He has provided for the little birds, not by building their nests, but by infusing into their nature that mysterious instinct which prompts them to build, and guides them in their work. Geologists, therefore, when they undertake to explain the existence of Stratified Eocks, not by the immediate action of the Creator, but by the intervention of natural causes, are not on that account to be accused of im- piety. They do not disparage, but rather magnify His glory, when they expatiate upon the endless variety of agents which, according to their theory, He has em- ployed in the structure of the material world. If the BUT RATHER MAGNIFIED BY GEOLOGY. 155 honeycomb, as a work of contrivance and design, ex- cites the wonder and admiration of the philosopher, what must we think of the contrivance and design exhi- bited by Him who has made not the honeycomb only, but the bee that builds the honeycomb ? And so, too, we get novel and unexpected views of God's Omnipo- tence, when, through the science of Geology, we come to understand the vast and harmonious series of secon- dary causes by which He has brought the Crust of the Earth into its present form and shape. The impress of His hand is stamped upon His works ; and all that is wonderful and attractive in Nature is but the token of His power and the shadow of His beauty. And so our national poet has sung : " Thou art, God, the life and light Of all this vondioua world we see ; Its glow by day, its smile by night, Are but reflections caught from Thee. Where'er we turn, Thy glories shine, And all things fair and bright are Thine." CHAPTER X. FOSSIL REMAINS — THE MUSEUM. llECAPITrLA.TION— SCOPE OP OUE ARGUMENT — THEORY OF STHATI- PIED BOCKS THE PBAMEWORK OP BEOLOQICAL SCIENCE — THIS THEOET BRINGS GEOLOGY INTO CONTACT WITH REVELATION — THE LINE OP EEASONINQ HITHERTO PDE8UED CONPIKMED BY THE TESTIMONY OP POSSIL REMAINS — ^MEANING OP THE WOED POSSIL INEXHAUSTIBLE ABUNDANCE OP POSSILS — TAEI0U8 STATES OP PRESERVATION — PETRI- PACTION — EXPERIMENTS OP PEOPESSOE GOPPERT — OEOANTO EOCKS APFOED SOME INSIGHT INTO THE POSSIL WORLD — THE EEALITY AND SIGNIFICANCE OP POSSIL REMAINS MUST BE LEARNED FROM OBSERVA- TION — THE BRITISH MUSEUM— COLOSSAL SKELETONS— BONES AND SHELLS OP ANIMALS — FOSSIL PLANTS AND TREES. " Reader, you are beginning to suspect us. ' How long do we purpose to detain people ? ' For anything that ap- pears we may be designing to write on to the twentieth century. ' And whither are we going? ' Towards what object ? which is as urgent a quoere as how far. Per- haps we may be leading you into treason. You feel symptoms of doubt and restiveness ; and like Hamlet with his father's ghost, you will follow us no further unless we explain what it is that we are in quest of." These words of Thomas De Quincey to his readers, in the middle of one of his discursive essays, which, inte- resting as they certainly are in all their parts, yet some- times beget a feeling of weariness from the uncom- fortable apprehension that they will never come to an RECAPITULATION. 1 5 7 end, are, perhaps, scarcely less appropriate in our own case. It may be that our readers have been left too long in the uneasy state of suspense and hope deferred. They came to our pages to look for a practical solution of the question. Is Geology at variance with the Bible ? and what avails it, they may ask, to discourse to them of the Gulf Stream, and Rivers, and Glaciers, and Alluvial Plains, and Coral Rocks, and Coal Mines ? With pain- ful steps they have been toiling after us through tedious disquisitions, straining their eyes to see the end, but the end is not yet in sight. "Well, then, if they will rest for a few minutes by the way, we will pause, too, and tell them what we are about, and try to bring out more clearly the object at which we are aiming. Our design from the beginning was to consider the points of contact between Geology and Revelation ; to examine the relations that exist between these two de- partments of knowledge, — one resting upon reason and observation, the other given to us from Heaven ; and to inquire how far it may be possible to adopt the conclu- sions of the former, while we adhere, at the same time, with unswerving fidelity, to the unchangeable truths of the latter. With this end in view, we proceeded at once to sketch out the more prominent features of Geological theory ; not the particular theory of one writer, or of one school, but that more general theory which is adopted by all writers, and prevails in every school. This theory, we were well aware, is in many points widely at vari- ance with the common notions of sensible and even well-informed men who have not devoted much attention 1 5 8 EECAPITULATION. to the study of Physical Science. And it occurred to us that, possibly, many of our readers might be disposed to cut the controversy short, by rejecting in a summary way the whole system of Geology, and treating it as an empty shadow or an idle dream. This, we were con- vinced, would be a mistaken and a mischievous course. Geology is not a house of cards that it may be blown down by a breath. It is a hypothesis, a theory, if you will ; but no one can in fairness deny that behind this theory there are facts, — unexpected, startling, significant facts ; that these facts, when considered in their relation to one another, when illustrated by the present pheno- mena of Nature, and skilfully grouped together, as they have been, by able men, disclose certain general truths, and suggest certain arguments, which do seem to point in the direction of those conclusions at which Geologists have arrived. It follows that he who would investigate fairly the claims of Geology, must first learn to appreciate the significance of these facts, and to estimate the value of these arguments. And this is precisely what we have been trying to do. We are not writing a treatise on Geology. Certainly not : it would be presumptuous in us, with our scanty knowledge, to attempt it. Besides, Geology has its own professors, and its lecture halls, and its manuals. Neither do we mean to assume the cha- racter of the advocates or champions of Geology. It does not ask our services ; in its cause are enrolled no small proportion of the most illustrious names which for the last fifty years have adorned the annals of Physical KEOAPITULATION. 159 Science. Nor do we want even to enforce upon our readers that more general theory of Geology which we are endeavouring to explain and to illustrate. Our pur- pose is merely to collect from various sources, and to string together, the evidence that may be adduced in its favour ; that so, when we come hereafter to consider this theory in its relation with the History of the Bible, we may not incur the risk of discomfiture by denying that which has been proved by facts, but rather approach the subject with such knowledge as may help us to dis- cover the real harmony, that we know must exist be- tween the truths inscribed on the works of God, and those which are recorded in His Written Word. In the accomplishment of this task we have devoted ourselves chiefly to the study of the Aqueous or Stratified Eocks. According to Geologists, these rocks, such as we find them now, were not the immediate work of creation, but were slowly produced in the long lapse of ages, and laid out one above another, by a vast and complex machinery of secondary causes. The elements of which they are composed were gathered together from many and various sources ; from the ocean, from the air, from other pre-existing rocks ; and, for aught we know,' may have had a long and eventful history before they came to assume their present structure and arrangement. Thus, for example, the Conglomerates, and Sandstones, with which we are so familiar, are made up of broken fragments derived from earlier rocks, and then transported to distant sites by the mountain torrents, or the stately rivers of vast continents, or the silent currents of the sea ; l6o THEORY OF STRATIFIED ROCKS. the Limestone with which we build our houses is the work of living animals that once swarmed in countless myriads beneath the waters of the ocean ; and the Coal which supplies the motive power to our manufactories, our railways, our ships of war and commerce, is but the modern representative of ancient swamps and forests, which, having been buried in the earth, and there, by the action of chemical laws, endowed with new properties, were laid by for the future use of man in the great store- house of Nature. This mode of accounting for the origin and formation of Stratified Rocks constitutes in a manner the frame- work that supports and binds together the whole system of Geology. If it be once fairly established. Geology is entitled to take high rank as a Physical Science. If on the contrary it should prove to be without foundation, then Geology is no longer a science, but a dream. More- over, it is this theory of stratification which, from the first, has brought Geology into contact with Revelation, For Geologists have been led to infer the extreme Anti- quity of the Earth, from the immense thickness of the Stratified Rocks on the one hand, and, on the other, the very slow and gradual process by which each stratum in the series has been, in its turn, spread out and consoli- dated. Those likewise who claim for the Human Race a greater Antiquity than the Bible allows, seek for their proofs in the supposed origin and antiquity of those sur- perficial deposits, in which the remains of Man or of his works are sometimes found entombed. It is not to be wondered at, therefore, that the theory LINE OF REASONING HITHERTO PURSUED. i6l of Stratified Rocks should engage the largest share of our attention when we undertake to discuss the relation in which Geology stands to Revealed Religion. For the present we say nothing about the conclusions that flow from this theory, or the errors to which it has led when hastily or ignorantly applied : we are only investigating the evidence by which it is supported. In our former chapters we have drawn out at some length the line of reasoning which is derived from the character of the Aqueous Rocks themselves, when considered in the light of Nature's present operations. We have shown that Stratified Rocks of many different kinds, just such as those which compose the Crust of the Earth, have been produced by natural causes within historic times ; and we have explained some of the more simple and intelligible parts of that complex machinery, which, even now, is busily at work gathering, sorting, distributing, piling up together, and consolidating the materials of new strata all over the world. These considerations, as we took oc- casion to point out, beget a strong presumption in favour of Geological theory. Here we have Nature at work, actually bringing into existence a stratum of rock before our eyes. And there, in the Crust of the Earth, we find another stratum of precisely the same kind already finished. "V\Tiat can be more reasonable than to ascribe the one to the action of the same causes which we see at work upon the other ? And thus, by extending the area of our observations from one class of Aqueous Rocks to another, the idea gradually grows upon us that these rocks have been spread out, stratum upon stratum, M 1 62 INDEPENDENT TESTIMONY OF FOSSIL REMAINS. during many successive ages, by the agency of secondary causes similar to those which are still in operation ; and that each stratum, in its turn, as it first came into exist- ence, was for a time the uppermost of the series. In support of this conclusion we are now about to bring forward a new and independent argument founded on the testimony of Fossil Eemains. An eminent writer has summed up in a few words the value and importance of Fossil Remains in reference to Geological theory. " At present," he says, " shells, fishes, and other animals are buried in the mud or silt of lakes and estuaries ; rivers also carry down the carcases of land animals, the trunks of trees, and other vegetable drift; and earth- quakes submerge plains and islands, with all their vege- table and animal inhabitants. These remains become enveloped in the layers of mud and sand and gravel fbrmed by the waters, and in process of time are petri- fied, that is, are converted into stony matter like the shells and bones found in the oldest strata. Now, as at present, so in all former time must the remains of plants and animals have been similarly preserved ; and, as one tribe of plant is peculiar to the dry plain, another to the swampy morass ; as one family belongs to a temperate, another to a tropical region, so, from the character of the imbedded plants, we are enabled to arrive at some knowledge of the conditions under which they flourished. In the same manner with animals : each tribe has its loca- lity assigned it by peculiarities of food, climate, and the like ; each family has its own peculiar structure for run- ning, flying, swimming, plant-eating or flesh-eating, as MEANING OF THE WORD FOSSIL. 163 the case may be; and by comparing Fossil Remains with existing races, we are enabled to determine many of the past conditions of the world with considerable cer- tainty."' On this branch of our subject we do not mean to offer much in the way of argument strictly so called. We shall content ourselves with a simple statement of facts, and leave them to produce their own impression. It will be necessary at the outset to explain some technical matters, that what we have to say hereafter may be the better understood : and if in this we are somewhat dry and tiresome, we will try to make amends by the curious and interesting story of Nature's long buried works, which we hope in the sequel to unfold. When the word Fossil was first introduced into the English language, it was employed to designate, as the etymology suggests, whatever is dug out of the earth.' But it is now generally used in a much more restricted sense, being applied only to the remains of plants and animals imbedded in the Crust of the Earth and there preserved by natural causes. When we speak of re- mains, we must be understood to include even tho'fee seemingly transient impressions, such as foot-prints in the sand, which having been made permanent by acci- dental circumstances, and thus engraved, as it were, on the archives of Nature, now bear witness to the former existence of organic life. ' Page, Advanced Text-Book of Geology, n. 7, pp. 20, 21. ' From the Latin Fossilis, dtig up. M 2 1 64 FOSSIL EEMAINS PRESERVED IN VARIOUS STATES. Now in every part of the world where the Stratified Rocks have been laid open to view, remains of this kind are found scattered on all sides in the most profuse abundance. In Europe, in America, in Australia, in the frozen wastes of Siberia, in the countless islands scattered over the waters of the Pacific, there is scarcely a single formation, from the lowest in the series to the highest, that, when it is fairly explored, does not yield up vast stores of shells, together with bones and teeth, nay sometimes whole skeletons of animals ; also frag- ments of wood, impressions of leaves, and other organic substances. These Fossil Remains do not always occur in the same state of preservation. Sometimes we have the bone, or plant, or shell, in its natural condition; still retaining not only its own peculiar form and structure, but likewise the very same organic substance of which it was originally composed. Examples innumerable may be seen in the British Museum, or, indeed, in almost any Geological collection : the fine skeletons of ancient Irish Deer, which are exhibited in the Mu- seum of Trinity College, Dublin, and of which all the bones are in excellent preservation, must be familiar to many of our readers. It happens, however, more frequently that the organic substance itself has disappeared, but has left an impres- sion on the rock, that now bears witness to its former presence. Thus, for instance, when a shell has been dissolved and carried away by water percolating the rock, it has very often left after it, on the hard stone, a FOSSIL REMAINS PEESEEVED IN VAEIOUS STATES. 1 65 mould of its outer surface and a cast of its inner surface, with a cavity between corresponding to the thickness Fig. 12. Fossil Irish Deer (County Fermanagli). In the Museum of Trinity College, Dublin. From Haughton'a Manual of Geology. of the shell. In such cases we have the form, the size, and the superficial markings of the organic body, but we have no part of its original substance, and 1 66 PKOCESS OF PETRIFACTION. no traces of its internal structure. This form of fossili- zation, as Sir Charles Lyell has well put it, " may be easily 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 consis- tency in 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."' In many cases the space first occupied by the shell is not left empty when the shell has been removed, but is filled up with some mineral substance such as lime or flint. The mineral thus introduced becomes the exact counterpart of the organic body which has dis- appeared ; and has been justly compared to a bronze statue, which exhibits the exterior form and lineaments, but not the internal organization nor the substance of the object it represents. There is a third form, more wonderful still, in which Fossil Remains are not uncommonly found. The origi- nal body has passed away as in the former case, and yet not only does its outward shape remain, but even its internal texture is perfectly preserved in the solid stone which has taken its place. This kind of change is exhibited most remarkably in the vegetable kingdom. Fossil trees of great size have been discovered of which the whole substance has been changed from wood to stone : yet with such exquisite skill has the change been effected that the minute cells and fibres, and the rings ' Elements of Geology, p. 38. PROCESS OF PETRIFACTION. 1 67 of annual growth, may still be clearly traced ; nay, even those delicate spiral vessels which, from their extreme minuteness, can be discerned only by the aid of the microscope. Thus the tree remains complete in all its parts ; but it is no longer a tree of wood ; it is, so to speak, a tree of stone. The mystery of this extraordinary tranformation has not yet been fully cleared up by scientific men ; but the general principle, at least, is sufficiently under- stood. It is thus briefly explained by Sir Charles Lyell : " 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 ele- ments, consisting usually of oxygen, hydrogen, nitrogen, and carbon. These will readily be absorbed by the atmosphere or be washed away by rain, so that all vestiges of the dead animal or plant disappear. But if the same substances be submerged in water, they de- compose more gradually, and if buried in the earth, still more slowly, as in the familiar example of wooden piles or other buried timber. Now, if as fast as each particle is set free by putrefaction in a fluid or gaseous state, a particle equally minute of carbonate of lime, flint, or other mineral is at hand and ready to be pre- cipitated, we may imagine this inorganic matter to take the place just before left unoccapied by the or- ganic 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 sufier a like transmutation."' This exposition, so simple and 1 Elements of Geology, p. 40. 1 68 EXPERIMENTS OF PROFESSOE GOPPERT. luminous in itself, may, perhaps, be rendered still more intelligible to the general reader by an ingenious illus- tration of Mr. Jukes. " It is," he says, " as if a house were gradually rebuilt, brick by brick, or stone by stone, a brick or a stone of a different kind having been substituted for each of the former ones, the shape and size of the house, the forms and arrangements of its rooms, passages, and closets, and even the number and shape of the bricks and stones, remaining un- altered."' • This singular kind of petrifaction, by which not only the external form, but even the organic tissue itself, is converted into stone, has been illustrated, in a very in- teresting way by Professor Goppert of Breslau. With a view to imitate as nearly as he could the process of Nature, " 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, were immersed in a moderately strong solution of sulphate of iron. When they had been thoroughly soaked in the liquid for several days, they were dried and exposed to a red heat until the vegetable matter was burnt up and no- thing remained but an oxide of iron, which was found to have taken the form of the deal so exactly that casts ' Manual of Geology, p. 375. GUNEBAL DESCRIPTION OF FOSSIL REMAINS. 169 even of the dotted vessels peculiar to this family of plants were distinctly visible under the microscope."' If we have succeeded in making ourselves under- stood, the reader will now have a pretty accurate no- tion of what is meant, in modern Geology, by Fossil Remains. They are the remains or impressions of plants and animals, buried in the earth by natural causes, and preserved to our time in any one of the three forms we have just described. Either the body itself remains, still retaining its own natural substance, together with its external form and its internal structure. Or secondly, the organic substance and the organic structure have both disappeared, but the outward form and the super- ficial markings have been left impressed on the solid rock. Or thirdly, the substance of the body has been converted into stone, but with such a delicate art, that it is in all respects, outwardly and inwardly, still the same body, with a new substance. We should observe, however, that these three different forms of fossilization, which we have successively described, are not always clearly distinct in actual fossil specimens, but are often curiously blended together according as the original organic substance has been more or less completely dis- placed, or the process of petrifaction has been more or less perfectly accomplished. ' Lyell, Elements of Geology, pp. 40-41. The reader will find a singu- larly clear and simple exposition of this subject in Doctor Haughton's Manual of Geology, Lecture III. ; an exposition which it was not our good fortune to have read until oiu' own brief summary was already in type. 1 yo A VISIT TO THE ORGANIC REMAINS It will probably have occurred to the intelligent reader that we have already had some insight into the Fossil world, when investigating the origin of Organic Rocks. We have seen, for instance, that Coal is the representative to our age of swamps and forests which once covered the earth with vegetation ; that Mountain Limestone is in great part formed from the skeletons of reef-building corals ; that the White Chalk of Europe is almost entirely derived from the remains of marine shells. But it should be observed that these and such like rocks, while they afford us much valuable infor- mation about the ancient organic condition of our planet, are not, strictly speaking, Fossil Kemains. For, not only does the substance of the organic bodies they represent exhibit an altered character, but the internal structure has been in great part effaced, and even the outward forms and superficial markings have disappeared. They contain, it is true, great multitudes of Fossils. In the Coal, for example, are found, as we have seen, trunks of trees, together with the impressions of plants and leaves : in the Chalk and Mountain Limestone, fragments of shells and corals are often discovered in a state of perfect preservation. But the bulk of these formations is made up not so much of Fossil Remains, as of that into which Fossil Remains have been con- verted. Coal, for instance, is something more than Fossil wood ; Chalk, and Limestone, and Marble, are something more than Fossil shells and corals. Fossil Remains properly so called present a very much more lively picture of the ancient inhabitants OF THE BRITISH MUSEUM. 171 of our Globe. But it is a picture that can but faintly be conveyed to the mind by the way of mere verbal de- scription. He who would appreciate aright the reality and the significance of Fossil Remains must gather his impressions from actual observation. Let him go, for instance, to the British Museum, and walk slowly through the long suite of noble galleries which are there exclusively devoted to this branch of science. He will feel as if transported into another world, the reality of which he could scarcely have believed if he had not seen it with his own eyes. Before him, and behind him, and on each side of him, as he moves along, are spread out in long array forms of beasts, and birds, and fish, and amphibious animals, such as he has never seen before, nor dreamt of in his wildest dreams. Yet much as he may wonder at these strange figures, he never for a moment doubts that they were once indued with life, and moved over the surface of the earth, or disported in the waters of the deep. Nay more, though the forms are new to him, he will be at no loss, however inexperienced in Natural History, to find many analogies between the creation in the midst of which he stands, and the creation with which he has been hitherto familiar. There are quadrupeds, and bipeds, and reptiles. Some of the animals were manifestly designed to walk on dry land, some to swim in the sea, and some to fly in the air. Some are armed with claws like the lion or the tiger, others have the paddles of a turtle, and others again have the fins of a fish. Here is an enormous beast that might almost 172 A VISIT TO THE ORGANIC REMAINS pass for an elephant, though an experienced eye will not fail to detect an important difference ; and there is an amphibious monster that suggests the idea of a cro- codile ; and again a little further on is an unsightly creature which unites the general characteristics of the diminutive sloth with the colossal proportions of the largest rhinoceros. If left to mere conjecture, the visitor would perhaps suppose that these uncouth monsters had been brought together by some adventurous traveller from the remote regions of the world. But no: he will find on inquiry that the vast majority belong to species which for centu- ries have not been known to flourish on the Earth ; and that many of the strangest forms before him have been dug up almost from beneath the very soil on which he stands,— from the quarries of Surrey, of Sussex, and of Kent, and from the deep cuttings on the many lines of railway that diverge from the great metropolis of Lon- don. The life they represent so vividly is, indeed, widely different from that which flourishes around us ; but it is the life not so much of a far distant country as of a far distant age. It must not be supposed, however, that such skeletons as those which first arrest the eye in the galleries of the British Museum — so colossal in their proportions and so complete in all their details — fairly exhibit the general character of Fossil Kemains. Perfect skeletons of gigan- tic animals are rarely to be found. They are the excep- tion and not the general rule,— the magnificent reward of long and toilsome exploration, or, it may be, the OF THE BRITISH MUSEUM. 173 chance discovery that brings wealth to the humble home of some rustic labourer. Very different are the common every day discoveries of the working Geologist. Dis- jointed bones and skulls, scattered teeth, fragments of shells, the eggs of birds, the impressions of leaves, — these are the ordinary reHcs that Nature has stored up for our instruction in the various strata of the Earth's Crust : and these likewise constitute by far the greater part of the treasures which are gathered together in our Geological Museums. We will suppose, then, that the visitor has gratified his sense of wonder in gazing at the larger and more striking forms, few in number, that rise up prominently before him, and seem to stare at him in return from their hoUow sockets: he must next turn his attention to the cases that stand against the walls, and to the cabinets that stretch along the galleries in distant perspective. Let him survey that multitude of bones of every shape and size, and those countless legions of shells, and then try to realise to his mind what a profusion and variety of animal life are here represented. And yet he must re- member that this is but a single collection. There are thousands of others, public and private, scattered over England, France, Germany, Italy, and, beyond the Atlantic, on the continent of America, and even in Aus- tralia; all of which have been furnished from a few isolated spots, — scarcely more than specks on the surface of the Globe, — where the interior of the Earth's Crust has chanced to be laid open to the explorations of the Geologist. I 74 A VISIT TO THE ORGANIC REMAINS Lastly, before he leaves this splendid gallery, let him take a passing glance at the Organic Remains of the vegetable world. There is no mistaking the forms here presented to his view. He will recognize at once the massive and lofty trunks of forest trees with their spread- ing branches ; the tender foliage of the lesser plants ; and, in particular, the graceful fern, which cannot fail to attract his eye by its unrivalled luxuriance. But if the forms are familiar, how strange is the substance, of this ancient vegetation ! The forest tree has been turned into sandstone ; many of the plants are of the hardest flint ; and the rich green of the fern has given place to the jet black colour of coal. Let him take a magnifying glass and scrutinize the internal structure of these mineralized remains ; for the more closely they are examined the Fig. 13. Foasil "Wood, from the Carboniferons Limestone of Mayo, showing the rings of Annual Growth. more wonderful do they appear. He can observe with- out difficulty their minute cells and fibres, the exact counterpart of those which may be seen in the plants that OF THE BRITISH MUSEUM. '75 are now growing upon the earth ; he may detect the little seed-vessels on the under surface o£the coaly fern ; nay, if he gets a polished transverse section of the sand- stone tree, he may count the rings that mark its an- nual growth, and tell the age it attained in its primeval forest. CHAPTER XI. FOSSIL RKMAINS— THE EXPLORATION. PROM THE MUSEUM TO THE dUAKBT — FOSSIL FISH IN THE LIMESTONE HOOKS OF MONTE BOLCA — IN THE QnARMES OP AIX — IN THE CHALK OF SUSSEX — THE ICHTHYOSAURUS OR FISH-LIKE LIZARD— GIGANTIC DIMENSIONS OF THIS ANCIENT MONSTER — ITS PREDATORY HABITS — THE PLESIOSAURUS — THE MEGATHERIUM OR GREAT WILD BEAST — HISTORY OF ITS DISCOVERY — THE MYLODON — PROFUSION OF FOSSIL SHELLS PETRIFIED TRE^B ERECT IN THE LIMESTONE ROCK OF PORT- LAND — FOSSIL PLANTS OF THE COAL MEASURES — THE SIGILLARIA — THE FERN — THE CALAMITB — THE LEPIDODENDRON— COAL MINE OF TREUIL — FOSSIL REMAINS AFFORD UNDENIABLE EVIDENCE OP FORMER ANIMAL AND VEGETABLE LIFE — THEIR EXISTENCE CANNOT BE AC- COUNTED FOR BY THE PLASTIC POWER OP NATUUE — NOR CAN IT REASONABLY BE ASCRIBED TO A SPECIAL ACT OP CREATION. From the galleries of the Museum we must now de- scend into the subterranean recesses of the mine and the quarry. For it is not enough to be familiar with the appearance of Fossil Kemains, as they are laid out for show by human hands : we must see them also as they lie embedded in the successive strata of the Earth's Crust, which are the shelves of Nature's cabinet. We shall begin with the celebrated quarries of Monte Bolca, in Northern Italy, not far from Verona. Here, in the hard limestone rock, fifty miles, from the nearest sea, entire skeletons of many diflferent species of fish are found imbedded in profuse abundance, and in a won- derful state of preservation. They lie parallel to the layers of the rock ; and, though flattened by pressure. FOSSIL FISH OF MONTE BOLCA. '77 still retain their scales, bones, fins, nay, even their muscular tissue, undisturbed and unharmed. Their Fig 14. Platax Papilio. From the limestone of Mqnte Boloa. N 178 FOSSIL FISH OF MONTE BOLCA. colour is a deep brown, which forms a remarkable contrast with the creamy hue of the limestone in Fig- 15. SemiophoruB Velicaos. From the limestone of Monte Bolca. which they are enveloped. The quarries have been worked only by students of Natural History for the sake of the Organic? remains, and are, therefore, of very FOSSIL FISH OP MONTE BOLCA. 179 limited extent ; yet so abundant are these fossil treasures that upwards of a hundred different species have been discovered, and thousands of specimens have been dis- persed over the cabinets of Europe. So closely are they sometimes packed together that many individuals are contained in a single block. From these facts Geologists have been led to con- clude; — that the strata in question were deposited on the bed of an ancient sea in which these fishes swam ; that the waters of the sea were suddenly ren- dered noxious, probably by the eruption of volcanic matter ; that the fishes in consequence perished in large numbers, and were then almost immediately im- bedded in the calcareous deposits of which the strata are composed. These views receive no small con- firmation from a very remarkable phenomenon to which we may be allowed, in passing, to call attention. In the year 1831a volcanic island was suddenly thrown up in the Mediterranean between Sicily and the African coast ; and the waters of the sea were at the same time observed to be charged with a red mud over a very wide area, while hundreds of dead fish were seen floating on the surface. Is it not pretty plain that when the mud subsided many of the fish were enveloped in the de- posit, and thus preserved to future times ? If so, then, we should liave an exact modern parallel to the fossil fishes of Monte Bolca. But for the present it is our pur- pose rather to describe facts than to develop theories.' 1 Buekland, Bridgewater Treatise, vol. i. p. 123 ; Mantell, Wonders of Geology, p. 269 ; Lyejl, Elements of Geology, p. 687. N 2 i8o FISH IN THE LIMESTONE ROCK OF AIX. Near the town of Aix, the ancient capital of Pro- vence, in the south of France, is a group of strata, con- sisting chiefly of Clonglomerate, Marl, Gypsum and Limestone, which has earned for itself no small fame in the annals of Geology. Besides many curious relics of an extinct vegetation, these strata yield also an abun- dance of Fossil Insects, which emerge from the rocky bed in which they have slept for ages, with a surprising freshness, and a life-like reality. But the quarries of Aix, like those of Monte Bolca, are chiefly famous for their Fossil Fish. And in this case too, as in the former, it would seem as if vast multitudes had suddenly perished together, from some mysterious cause, and Fig. i6. Fossil Fish from Aix. were then as suddenly entombed. They exhibit no mark of mechanical violence : and yet they are found, FISH IN THE CHALK OF SUSSEX. l8l not unfrequently, crowded together as closely as they can fit, in every variety of position, on the same slab of limestone. A good example of such a block is repre- sented in our wood-cut. The White Chalk Rock of Sussex has been rendered classical to the students of Geology by the skilful and laborious researches of the late Doctor Mantell. Pre- vious to his time the Fish of the Chalk were known only by their teeth and bones, which abounded in every quarry. But he succeeded in bringing to light many whole skeletons, and disengaging them without injury from their chalky envelopment. In many cases these Fossil Fish appear to have suffered little from compres- sion : the body still retains its rounded form ; and even Fig. 17. Beiyx Lewesiensis, from the Chalk, near Lewes, the most delicate scales and fins are as little disturbed or distorted as if the original had been surrounded by soft Plaster of Paris while floating in the water. For many 1 82 THE ICHTHYOSAURUS. years Doctor Mantell devoted himself with indefatigable zeal to the gathering of these interesting remains : and his masrnificent collection now stdorns the Galleries of the British Museum. In the annexed illustration is figured a specimen belonging to one of the most abundant species. It is closely allied to the common perch; and is popularly called Johnny Dory by the quarrymen of Sussex, but is entitled Beryx Lewesiensis by the learned." From Fossil Fish we now turn to Fossil Reptiles. Many of our readers have, perhaps, heard or read some- thing about an important group of rocks known by the name of the Lias. This Formation is well developed in England, and has received much attention from Geolo- gists. It stretches in a belt of varying width from Whitby on the coast of Yorkshire to Lyme Regis on the coast of Dorsetshire ; passing in its course through the counties of Leicester, Warwick, Gloucester, and Somerset. It is composed chiefly of Limestone, Marl, and Clay ; and is celebrated for the number and size of its great Fossil Reptiles. Of these the most remarkable is the Ichthyosaurus or Fish-like Lizard. This monster of the ancient seas combined, as its name denotes, the essential characters of a reptile with the form and habits of a fish. No such creature has been known to exist within historic times ; nevertheless, all the various parts of its complicated structure have their analogies, more or less perfect, in the present ' Mantell, Wonders of Geology, Lecture iv., FosbUs of the British Mu- seum, chapter v. ; see also Medals of Creation, and Fossils of the South Downs, by the same Author. 1 84 THE ICHTHYOSAURUS. creation. It had the head of a Lizard, the beak of a Porpoise, the teeth of a Crocodile, the back bone of a Fish, and the paddles of a Whale. In length it some- times exceeded thirty feet ; it had a short thick neck, an enormous stomach, a long and powerful tail. This last appendage, together with four great paddles or fins, constituted the chief organs of motion. But of all its parts the head was perhaps the most wonderful and characteristic. In the larger species the jaws were six feet long, and were armed with two rows of conical sharp-pointed teeth, — a hundred below, a hundred and ten above. The cavities in which the eyes were set measured often fourteen inches across, and the eye- balls themselves must have been larger . than a man's head. Now what we want particularly to impress upon our readers is, that the remains of this singular aquatic rep- tile abound throughout the whole extent of the Lias For- mation in England. Far down below the surface of the earth they are found imbedded in the marls, and clays, and limestones of Dorsetshire, and Gloucester, and Warwick, and Leicester, and Yorkshire. Sometimes whole skeletons are found entire with scarcely a single bone removed from the place it occupied during life ; but more frequently the scattered fragments are found lying about in a state of confused disorder ; — skulls, and jaw-bones, and teeth, and paddles, and the joints of the vertebral column and of the tail. The neighbourhood of Lyme Kegis is a perfect cabinet of these curious treasures. In some of the specimens there exhumed, a CONTENTS OF HIS STOMACH PRESERVED. 185 singular circumstance has been observed, which is de- serving of especial notice. We should naturally have expected, from the prodigious power of this animal, from the expansion of his jaws and the immense size of his stomach, that he preyed upon the other fish and reptiles that had the misfortune to inhabit the waters in which he lived. And so indeed it was. For here enclosed within his vast ribs, in the place that once was his sto- mach, are still preserved the remains of his half-digested food ; and amidst the debris we can distinguish the bones and scales of his victims. Nay, in some of the more colossal specimens of this ancient monster, we can distinctly recognize the remains of his own smaller bre- thren ; which, though less frequent than the bones of fishes, are still sufficiently numerous to prove that, when he wanted to appease his hunger, he did not even spare the less powerful members of his own species.' It is with facts like these, which are revealed by the Crust of the Earth all over the world, that Geologists are called upon to deal. When they meet with skele- tons and bones such as we have been describing, buried deep in the hard rock, hundreds of feet beneath the green grass, and the waving corn, they cannot help but ask the question : Where did these creatures come from ? When did they live ? And by what revolutions were they imbedded here, and lifted up from beneath the waters of the deep ? ' Owen's Palaeontology, pp. 200-9 i Buckland, Bridgewater Treatise, vol. i., pp. 168-186; ManteU, "Wonders of Geology, pp. 576-581 ; LyeU, Elements of Geology, pp. 420-425 ; Jukes, Manual of Geology, pp. 598- 599- 1 86 THE PLESIOSAURUS. In the same formation are found the remains of another ancient reptile, called the Plesiosaurus, that is to say, nearly allied to the Lizard. Of this extraordi- nary monster Cuvier observed that its structure was the most singular and anomalous that, up to his time, had been discovered amid the ruins of the ancient world. It is chiefly distinguished from the Ichthyosaurus, to which it has no small affinity, by the enormous length of its neck, which in some species resembles the body of a serpent. Dr. Buckland tells us that in the Plesiosaurus Dolichodeirus the neck is longer than the trunk ; the one being five times, the other only four times, as long as the head. Our illustration, for which we are indebted to the kindness of Doctor Haughton, represents a fine speci- men of Plesiosaurus Cramptonii, which was found in the Lias Beds of Kettleness, near Whitby, in Yorkshire, and which is now a prominent object in the Museum of the Royal Dublin Society. The habits and character of the Plesiosaurus have been thus sketched out by Mr. Conybeare : — " That it was aquatic is evident, from the form of its paddles ; that it was marine is almost equally so, from the remains with which it is universally associated ; that it may have occasionally visited the shore, the resemblance of its ex- tremities to those of the turtle may lead us to conjec- ture. Its motion, however, must have been very awk- ward on land; its long neck must have impeded its progress through the water ; presenting a striking con- trast to the organization which so admirably fits the Ichthyosaurus to cut through the waves. May it not 1 88 PAMPAS OF SOUTH AMERICA . therefore be concluded (since, in addition to these cir- cumstances, its respiration must have required frequent access of air), that it swam upon or near the surface ; arching back its long neck like the swan, and occasion- ally darting it down at the fish which happened to float within its reach. It may perhaps have lurked in shoal water along the coast concealed among the sea-weed, and raising its nostrils to a level with the surface from a considerable depth, may have found a secure retreat from the assaults of dangerous enemies ; while the length and flexibility of its neck may have compensated for the want of strength in its jaws, and its incapacity for swift motion through the water, by the suddenness and agility of the attack which they enabled it to make on every animal fitted for its prey, which came within its reach.'" The Pampas of South America are not less famous in Geology for the remains of gigantic quadrupeds, than the Lias of England for its colossal marine reptiles. These vast undulating plains, which present to the eye for nine hundred miles a waving sea of grass, consist chiefly of stratified beds of gravel and reddish mud : and it is in these beds that the remains of many unshapely but powerful terrestrial animals have been found im- bedded. So abundant are they, that it is said a line drawn in any direction through the country would cut through some skeleton or bones. Indeed Mr. Darwin is of opinion that the whole area of the Pampas is one wide sepulchre of these extinct animals. It will be ' Buckland's Bridgewater Treatise, vol. i. pp. 202-14; Owen's Paleon- tology, 223-232. THE MEGATHEEIUM OR GREAT WILD BEAST. 1 89 enough for our purpose to describe one in particular, which from its prodigious bulk has received the appro- priate name of Megatherium, or the Great Wild Beast. The Megatherium, like the Ichthyosaurus and the Plesiosaurus, had many affinities with the existing creation. In its head and shoulders it resembled the sloth which still browses on the green foliage of the trees in the dense forests of South America ; while in its legs and feet it combined the characteristics of the Ant- . Eater and the Armadillo. But it was eminently distin- guished from these and all the other modern represen- tatives of the family to which it belonged by its colossal proportions. It was often twelve feet long and eight feet high ; its fore-feet were a yard in length and twelve inches in breadth, terminating in gigantic claws ; its haunches were five feet wide, and its thigh bone was three times as big as that of the largest elephant. " His entire frame," as Dr. Buckland has admirably observed, and carefully demonstrated, " was an appara- tus of colossal mechanism, adapted exactly to the work it had to do ; strong and ponderous, in proportion as this work was heavy, and calculated to be the vehicle of life and enjoyment to a gigantic race of quadrupeds, which, though they have ceased to be counted among the living inhabitants of our planet, have, in their fossil bones, left behind them imperishable monuments of the consum- mate skill with which they were constructed, — each limb, and fragment of a limb, forming co-ordinate parts of a well adjusted and perfect whole ; and through all their deviations from the form and proportions of the limbs 1 90 THE MEGATHERIUM OR GREAT WILD BEAST. of Other quadrupeds, affording fresh proofs of the infi- nitely varied and inexhaustible contrivances of Creative Wisdom." This Leviathan of the Pampas, as has been justly called, became first known in Europe towards the close of the last century. In the year 1789 a skeleton was dug up, almost entire, about three miles south-west of Buenos Ayres, and was presented by the Marquis of Loreto to the Royal Museum at Madrid, where it still remains. Since that time other specimens, besides nu- merous fragments, have been discovered, chiefly through the zeal and energy of Sir Woodbine Parish ; by the aid of which the form, structure, and consequently the habits of this clumsy and ponderous animal have been fully ascertained. The complete skeleton which forms so prominent an object of attraction in the British Mu- seum, and which is represented in the woodcut on the adjoining page, is only a model ; but it has been con- structed with great care from the original bones, some of which are to be found in the wall-cases of the same room, and others in the Hunterian Museum of the Eoyal College of Surgeons."' Closely allied to the Megatherium, but somewhat less colossal in its dimensions, is the Mylodon. Its remains are found associated with those of the Megatherium and other great animals of the same family, in the super- ' Buckland, Bridgewater Treatise, vol. i. pp. 139-164 ; Owen's PalsBOn- tology, pp. 390-2 i Mantell, Wonders of Geology, pp. 166-9 > Fossils of the British Museum, pp. 465-480; The English Cyclopsedia, Natural History Division, Article, Megatheridse. 192 THE MYLODON. ficial gravels of South America. A splendid specimen, which measures eleven feet from the fore part of the skull to the end of the tail, was dug up, in the year 1841, Fig. 22. Mylodon Eobustus, from Buenos Ayres. a few miles north of Buenos Ayres. It is well figured in the adjoining woodcut, which we reproduce, by kind permission of the Author, from Dr. Haughton's admi- rable Manual of Geology. FOSSIL SHELLS. 193 Passing from the petrified fish, and the reptiles, and the quadrupeds, that thus come forth as it were from their graves to bring us tidings of an extinct creation, we must next turn our attention for a moment' to Fos- sil Shells. These relics of the ancient world, which are scattered with profuse abundance through all the strata of the Earth's Crust, may seem, indeed, of little value to the careless observer ; but to the practised eye of science they are full of instruction. They have been aptly called the Medals of Creation ; for stamped upon their surface they bear the impress of the age to which they belong ; and they constitute the largest, we may say perhaps, the most valuable part of those un- written records from which the Geologist seeks to ga- ther the ancient history of our Globe. As regards the prodigious abundance of Fossil Shells preserved in the Crust of the Earth, it is unnecessary for us here to speak. We have already seen that the great mass of many limestone formations is composed almost exclusively of such remains, broken up into minute fragments, and more or less altered by chemical agency ; and besides, there are quarries within the reach of all, where they may collect at pleasure these inte- resting relics of the olden time. But there are one or two facts of peculiar significance connected with Fossil Shells, which it may be useful briefly to set down. In the first place, we would remind our readers that there is a marked and well known difference between the shells of those animals that can live only in the sea, of those that inhabit rivers, and of those, finally, that 194 MARINE SHELLS ON LOFTY MOUNTAINS. frequent the brackish waters of estuaries. Now it has been made clear beyond all reasonable doubt, by the explorations of Geologists, that sea-shells abound in great numbers far away from the present line of coast, in the heart of vast continents. And they are found, not merely on the surface, but buried deep in the Crust of the Earth, and overlaid in many cases by numerous strata of solid rock, thousands of feet in thickness. It is also to be observed that they occur at all heights above the level of the ocean; having been discovered at an elevation of eight thousand feet in the Pyrenees, ten thousand in the Alps, thirteen thousand in the Andes, and above eighteen thousand in the Himalaya.* Such are the phenomena which are con- stantly forcing themselves on the attention of the Geo- logist, and which involve a number of problems that he cannot help attempting to investigate and explain. He is instinctively impelled to ask himself, how can the shells of marine animals have come to exist so far away from the sea ? how have they been buried in the Crust of the Earth? how have they been lifted up to the highest pinnacles of lofty mountains ? Our subterranean exploration would be incomplete if it did not illustrate the Vegetable as well as the Animal Life of the ancient world. Let the reader then descend in fancy into the celebrated quarries of Portland on the south coast of England, and he will see the fossilized remains of a long past vegetation exhibited in a very ' Lyell, Elements of Geology, p. 4. PETEIFIED FOREST OF PORTLAND. 195 striking manner. In one of these quarries a vertical section, extending from the surface downwards to the depth of about thirty feet, presents the following suc- cession of strata arranged in horizontal layers : — first, a Fig. 23- Vegetable soil. } Fresh- water Lime- stone. Clay. Laminated fresh- water Limestone. Dirt-bed with fossil trees and plants. Fresh-water Lime- stone. Section of a Quarry in the Island of Portland, thirty feet. Bed of Clay. Portland building stone full of ma- rine shells. Total thickness about light covering of vegetable soil, beneath which are thin beds of cream-coloured limestone, forming a stratum of solid rock ten feet thick ; then a bed of dark brown loam, mixed with rounded fragments of stone, and vary- ing in thickness from twelve to eighteen inches. This is known to the quarrymen by the name of Dirt-bed, 2 196 PETRIFIED FOREST OF PORTLAND. and seems, in former ages, to have supported a luxu- riant vegetation; for all around are scattered the pe- trified fragments of an ancient forest. The prostrate stems and shattered branches of great trees are met at every step ; but what is most striking and peculiar is, that, in many cases, the petrified stumps are still stand- ing erect, with their roots fixed in the thin stratum of loam, and their trunks stretching upwards into the hard limestone rock. Immediately below the Dirt-bed is another thick stratum of limestone, and below this again is a stratum of the famous Portland stone, so highly prized for building purposes. As the quarries of Portland are worked chiefly for the sake of this build- ing stone, little attention is paid to the Dirt-bed and its contents, which are commonly .thrown aside by the quarrymen as rubbish. The scene of this petrified forest is thus described by Doctor Mantell: — "On one of my visits to the island the surface of a large area of the Dirt-bed was cleared preparatory to its removal, and the appearance pre- sented was most striking. The floor of the quarry was literally strewn with fossil wood, and before me was a petrified forest, the trees and plants, like the inhabitants of the city in Arabian story, being converted into stone, yet still remaining in the places which they occupied when alive ! Some of the trunks were surrounded by a conical mound of calcareous earth, which had, evi- dently, when in the state of mud, accumulated round the roots. The upright trunks were generally a few feet apart, and but three or four feet high ; their summits VEGETABLE REMAINS OF THE COAL. '97 were broken and spKntered, as if they had been snapped or wrenched off by a hurricane at a short distance from the ground. Some were two feet in diameter, and the united fragments of one of the prostrate trunks indicated a total length of from thirty to forty feet ; in many spe- cimens, portions of the branches remained attached to the stem."» The Coal Measures of Europe and America offer to the student of Geology a boundless field for the investi- gation of Fossil Plants and Trees. We have already had occasion to notice the Sigillaria. This ancient tree, re- markable for its beautiful sculptured stem, has no exact representative in the vegetable kingdom of the present day. But it abounds everywhere in the Coal Measures ; and there seems little doubt that several great seams of Coal are composed almost entirely of its carbonized re- mains. Indeed the ancient soil, which commonly con- stitutes the floor on which the bed of Coal reposes, is often as thickly crowded with the branching roots of the Sigillaria, as the soil of a dense forest with the roots of the trees by which it is covered. The stem itself, when converted into Coal, generally assumes the form of long narrow slabs ; having been flattened by pres- sure during the process of mineralization. Sometimes, however, it is found uncompressed and erect. In this case the interior of the trunk is usually observed to have been filled up with sand or clay : and thus the forest tree, still retaining its external shape and character, is transformed into a cylindrical shell of carbonized bark without, and a solid cylinder of sandstone or shale 1 Wondei-s of Geology, p. 400. 198 THE FERN AND THE CALAMITE. within. An interesting example is exhibited in our illustration, Figure 11. Every Coal mine, too, is adorned with the imprint of the graceful Fern, which constitutes one of the most at- tractive features in the Flora of the ancient world. Not Fig. 24. Calamites Kodosua. From the Coal Measures of Newcastle. unfrequently it assumes a tree-like character, as it often does even now in tropical countries; and then, indeed, it is an object of striking beauty, reaching to a height of forty or fifty feet, and expanding at the sum- mit into an elegant canopy of foliage. The Calamite is another plant in which the Coal FOREST TREE ERECT IN A COAL MINE. 199 abounds. Its true botanical character is not yet clearly ascertained ; but it bears a general resemblance, except for its gigantic dimensions, to the common Horse-tail of our swamps and marshy grounds. It is a reed-like, jointed stem, sometimes thirty feet in length, hollow within, and curiously jointed without. Fig. 25. Lepidodendron Stembergii ; a Fossil Tree, 39 feet high. From a Coal Mine near Newcastle. Scarcely less conspicuous than the Sigillaria, the Fern, and the Calamite, is the Lepidodendron or Scaly Tree, 200 LEPIDODENDKON. one of the most curious and interesting among the plants of the Coal-bearing period. Like the Sigillaria and the Calamite it has been, and still is, a puzzle to the student of Botany. But it needs not the eye of science to see that it is unmistakably a stately forest tree, shut up in the Crust of the Earth, encased in a solid framework of in- durated Shale, or Sandstone, or Coal, as the case maybe, and overlaid with massive strata of rock hundreds of feet Fig. i6. Lepidodeudron Elegaus. Portion of Stem and branches ; Coal Mine, Newcastle. in thickness. Such a specimen as that represented in our woodcut was laid bare some years ago inYarrow Colliery, near Newcastle. ANCIENT FOREST ENVELOPED IN SANDSTONE. 201 In the same neighbourhood was found a portion of the stem and branches of another variety, Lepidodendron Elegans, which will enable the reader to form a more complete idea of the appearance presented by this an- cient tree as it stood in its primeval forest. An unusually favourable illustration of our present subject may be seen at the colliery of Treuil, in France, Fig. 27. Section of a Coal sandstone at Treuil, near Lyons. Showing the erect position of Fossil Trees. (Alex. Brongniart.) not far from the city of Lyons. The beds of Coal are overlaid by a kind of slaty sandstone, ten feet thick ; and this sandstone is traversed by the vertical stems of enor- mous petrified plants, chiefly Calamites. Here then, to all appearance, we have an ancient forest enveloped in 202 FOSSIL REMAINS NOT PEODUOED BY sandstone. "We must suppose that the forest was sub- merged while the trees were still erect ; that, in this con- dition, it received the sedimentary deposits carried down by the current of some great river ; and finally, that these deposits were, in the course of ages, compacted into sandstone by a process already explained. It would seem that after the sandstone had been partially, at least, consolidated, it was subjected to a sliding movement here and there, by which the continuity of the stems was broken ; the upper part, being pushed on one side as shown in our Figure. It is time we should bring to a close our survey, mea- gre and imperfect as it is, of Fossil Remains. Those who desire to pursue the inquiry for themselves will easily find an opportunity of doing so. There are few, we should suppose, who may not, occasionally, have access to one or other of those splendid Museums of Geology, which have been set up in all the great towns of Europe. And the still more extensive cabinets of Nature's Mu- seum, spread out beneath our feet, are within the reach of all. But even the scanty facts which have been set forth faithfully, we trust, though perhaps feebly, in these pages, are sufficient to satisfy all reasonable minds that the bones, the skeletons, the trunks and branches of trees, which have been exhumed from the Stratified Rocks, are really the remains of Organic Life that once flourished on the earth, or in the waters of the ancient seas. Obvious, however, as this fact must appear to all THE PLASTIC POWER OF NATURE. 203 who have fully realized the character and appearance of Fossil Remains, it has been often vigorously assailed and vehemently denounced. In the early days of Geology phenomena of this kind were ascribed, not uncommonly, to the " plastic power of Nature," or to the influence of the stars. Such notions, however, meet with little support among modern writers. They were nothing more than wild fancies, without any foundation either in the evidence of facts or in the analogy of Nature. The "plastic power of Nature" was a phrase that soixnded well, perhaps, in the ears of unreflecting peo- ple ; but no one ever undertook to show that Nature really possesses that " plastic power" which was so rea- dily imputed to her. No one ever undertook to show that it is the way of Nature to make the stems, and branches, and leaves of trees, without the previous pro- cess of vegetation ; or to make bones and skeletons which have never been invested with the ordinary appendages of flesh and blood. Yet surely this is a theory that requires proof; for all our experience of the laws of Nature points directly to the opposite conclusion. And as for the influence of the stars, we may be content to adopt the language of the celebrated painter Leonardo da Vinci: — "They tell us that these shells were formed in the hills by the influence of the stars ; but I ask where in the hills are the stars now forming shells of distinct ages and species? and how can the stars explain the origin of gravel occurring at different heights and composed of pebbles rounded as if by the action of running water ? or in what manner 204 FOSSIL REMAINS NOT CREATED can such a cause account for the petrifaction in the same places of various leaves, sea-weeds, and marine crabs."' In modern times the form of objection has been somewhat changed. We are told by some writers that, when we seek to explain the existence of Fossil Remains by the action of natural laws, we seem to forget the Omnipotence of God. They urge upon us, with much solemnity, that He could have made bones, and shells, and skeletons, and petrified wood, though there had been no living animal to which these bones belonged, and no living tree that had been changed into stone. And if He made them, might He not disperse them up and down through His creation, on the lofty mountains, in the hidden valleys, and in the profound depths of the sea ? and buried them in the limestone rocks and in the soft clay ? and arranged them in groups, or scattered them in wild confusion as He best pleased ? To this line of argument we must be content to reply, that we have no wish to limit the power of God. But we have learned from our daily experience that in the physical world He is pleased to employ the agency of secondary causes ; and when we know that for many ages a certain effect has been uniformly produced by a certain cause, and not otherwise, then if we again see the effect, we infer the cause. When a traveller in the untrodden wilds of Western America, comes upon a ' See Lyell, Principlea of Geology, vol. i., p. 31, who refers to Da Vinoi'e MSS. now in the Library of the Institute of France. IN THEIR PRESENT CONDITION. 205 forest of great trees, or a herd of unknown animals, surely lie never thinks of supposing that the wild beasts and the forest trees came directly from the hand of the Creator, in that state of maturity in which he beholds them. And why ? for it might be argued that the power of God is unbounded, and he might have created them as they now are if He had so pleased. Is it not that the traveller is impelled, by an instinct of his nature, to interpret the works of God which he now sees for the first time, according to the analogy of those with which he has been long familiar ? Now this is just the princi- ple for which we are contending. According to all our experience of the works of God in the physical world, the living body comes first, and the skeleton afterwards ; the living tree comes first, and afterwards the prostrate trunk and the splintered branches. There- fore when we meet with a skeleton, we conclude that it was once a living body ; and when we find the petrified stems, and branches, and leaves of trees, we have no doubt that they are the remains of an ancient vege- tation. But, in truth, if any one, with all the facts of the case fully before his mind, were deliberately to adopt this theory, that Fossils, as we find them now, were created by God in the Crust of the Earth, we candidly confess we have no argument that we should think likely to shake his conviction ; just as we should be utterly at a loss if he were to say that the Pyramids of Egypt, or the colossal sculptures of Nineveh, or the ruins of Baalbec, were created by God from the beginning. The 206 FACTS MORE CONVINCING THAN ARGUMENT. evidence of human workmanship is certainly not more clear in the one case, than is the evidence of animal and vegetable life in the other. We believe, however, that no such persons are to be found ; that theories of this kind have their origin, not so much in false reasoning, as in imperfect knowledge of facts ; and we have, there- fore, judged it most expedient not to spend our time in a discussion of philosophical axioms, but to set forth the facts, and leave them to speak for themselves. CHAPTER XII. GEOLOGICAL CHRONOLOGY — PRINCIPLES OP THE SYSTEM EXPLAINED AND DEVELOPED. SIQNIPICANOE OF POSSIL EEMAINS — SCIENCE OP PAI/iEONTOLOQY — OLASSIPIOATION OP EXISTING ANIMAL LIFE — FOSSIL REMAINS ARE FOUND TO FIT IN WITH THIS CLASSIFICATION — SUCCESSION OP OBGANIO LIFE — TIME IN GEOLOGY NOT MEASURED ET TEARS AND CENTURIES — SUOCESSITB PERIODS MARKED BY SUCCESSIVE POEMS OP LIFE — THE GEOLOGIST AIMS AT ARRANGING THESE PERIODS IN CHRO- NOLOGICAL ORDER — POSITION OP THE VARIOUS GROUPS OF STRATA NOT SUFFICIENT FOR THIS PURPOSE — IT IS ACCOMPLISHED CHIEFLY THROUGH THE AID OP FOSSIL REMAINS — MODE OF PROCEEDING PRAC- TICALLY EXPLAINED — CHRONOLOGICAL TABLE. The existence of Fossil Eemains is, then, a fact. Go where you will through the civilized world, and every chief town has its Museum, into which they have been ga- thered by the zeal and industry of man ; descend where you can into the Crust of the Earth, — the quarry, the mine, the railway cutting, — and there, notwithstanding the plunder which has been going on for two centuries and more, you will find that the inexhaustible cabinets of Nature are stiU teeming with these remains of ancient life. When we are brought, for the first time, face to face vnth these countless relics of a former world, we are im- pressed with a sense of wonder and bewilderment. That the skeletons before us, though now dry and withered. 208 SIGNIFICANCE OF FOSSIL REMAINS. were once animated with the breath of life ; that the trees now lying shattered and prostrate, and shorn of their branches, once flourished on the earth, we cannot for a moment hesitate to believe. But beyond this one fact, all is darkness and mystery. These gaunt skele- tons, these uncouth monsters, these petrified forests, are silent, lifeless, as the rocks within whose stony bosoms they have lain so long entombed. Had they speech and memory, they could tell us much, no doubt, of that an- cient world in which they bore a part, of its continents, and seas, and rivers, and mountains ; of the various tribes of animals and plants by which it was peopled ; of their habits and domestic economy ; how they lived, how they died, and how they were buried in those graves from which, after the lapse of we know not how many ages, they now come forth into the light of day. As it is, however, we can but gaze and wonder. We have nothing here but the relics of death and destruction : there is no feeling, no memory, no voice, in these dry bones ; no living tenant in these hollow skulls, to re- count to us the history of former times. So thinks and reasons the ordinary observer. But far difierent is the language of the Geologist. These dry and withered bones, he tells us, are gifted with memory and speech ; and, though the language they speak may seem at first unfamiliar and obscure, it is not, on that ac- count, beyond our comprehension. Like the birds, rep- tiles, fish, and other symbols, inscribed on the obelisks of ancient Egypt, these bones and shells stored up in the Crust of the Earth, have a hidden meaning which it PALEONTOLOGY. 209 is the business of Science to search out and explain. They are Nature's hieroglyphics, which she has im- pressed upon her works to carry down to remote ages the memory of the revolutions through which our Globe has passed ; and when we come to understand them aright, they do unfold to us the story of that ancient world to which they belonged. The interpretation of Fossil Kemains is, then, an im- portant department of Geology. Of late years it has been admitted to the rank of a special science, under the name of Palaeontology, which means, as the word de- notes — naXaiwv ovrwv X070C — the science which is con- cerned about the organic remains of ancient life. The honour of having been the first to place this science on a solid basis, in fact we may say the honour of having brought it into existence, is justly accorded to the dis- tinguished Cuvier, whose name shed a lustre upon France during the early years of the present century. It is therefore still in its infancy ; but it has already rewarded the zeal of its students by many wonderful and unex- pected revelations. We purpose in the first place to exa- mine the principles on which it is founded, and then to take a rapid glance at the conclusions to which it has led. At the outset it is worthy of notice that the very existence of Fossil Kemains, buried deep in the Crust of the Earth, forcibly confirms the Geological the- ory of Stratified Eocks. These rocks, as the reader will remember, are said to have been slowly spread out, one above another, during the lapse of many ages, by the operation of natural causes ; and we p 210 FOSSIL REMAINS CONFIKM THE have seen how this doctrine is supported by argu- ments founded on an examination of the rocks them- selves, — of the materials that compose them, and of the way in which these materials are piled together. Now let us observe how clearly the testimony of Fossil Eemains seems to point in the same direction. First, the bones and shells which we now find in such profusion, far down beneath the superficial cover- ing of the Earth, must have belonged to animals which, when living, flourished on what was then the surface. Yet now they are buried in the bosom of the hard rock, and covered over with beds of solid limestone, and sand- stone, and conglomerate, hundreds and thousands of feet in thickness. How can we explain this fact, unless we suppose that these animals, when they perished, were imbedded in some soft materials, which afterwards became consolidated, and above which, in the course of ages, more and more matter was deposited, until at length that lofty pile of strata was produced, beneath which the remains are now found buried ? Again, it is part of our theory that the formation of Stratified Rocks took place, for the most part, under water. The Organic Remains, therefore, which we should naturally expect to find preserved in the strata of the earth, would be those of aquatic animals ; or, if the remains of land animals were to be looked for, it should be of those chiefly which live near the banks of rivers and estuaries, and which, after death, might have been carried down by the current and buried in the silt and mud with which almost all rivers are charged THEORY OF STRATIFIED ROCKS. 2 l I at certain seasons of the year. We know as a fact that such animals are buried at the present day in the Deltas of the Ganges and the Mississippi ; and it would be reasonable to suppose that the same should have occurred in former ages. Now here again the evidence of Fossil Remains exactly fits in with our theory. For the vast bulk of them are manifestly the remains of animals that lived in water ; and the terrestrial animals, comparatively few, whose bones are preserved in the Crust of the Earth, are such as frequent the banks of great rivers or the marshy swamps of estuaries. Thus much we may learn even from a cursory glance at Fossil Remains, But these curious monuments of ancient times have a deeper meaning, which cannot be unfolded without a more minute and laborious inves- tigation. Our readers are aware that all the animals at present existing on the face of the Earth have been scientifically grouped together, according to certain well-marked characteristics, into various Kingdoms, Classes, Genera, and Species. Thus, for example, the horse and the dog are two different Species, belonging to the same Class of Mammalia ; the eagle and the sparrow are two different .Species of the same Class called Birds. Then again the Class of Mammalia and the Class of Birds both belong to the one common Kingdom of Vertebrata ; because, though different in many other respects, they agree in this, that all the members of both Classes have a vertebral or spinal column, to which the other parts of the internal skele- ton are attached. P 2 2 1 2 RESEARCHES OF CUVIER. Now when Cuvier began to examine closely the Organic Eemains of former times, to which his atten- tion was called by the bones dug up in the gypsum quarries of Montmartre, near Paris, about the close of the last century, he brought with him to the task a very large acquaintance with the various forms of hfe that, in the present age, prevail throughout the world. And he was greatly struck with the marked difference between those living animals with which he had been long familiar, and those with which he now became acquainted for the first time. The more he extended his researches, the more manifest did this difference appear ; until at last it became quite clear that the great bulk of the animals whose remains are preserved in the Crust of the Earth, have no representatives now living on its surface. Nevertheless, he observed that, though the Species no longer exists, it often happens that we have still other Species of the same Genus ; or if the Genus, too, be extinct, we have other Genera of the same Class. Here, then, is the first great truth at which Cuvier arrived, and which has been since confirmed by extensive observations :— that the animals which formerly dwelt on this Earth of ours, were, for the most part, widely different from those by which it is now inha- bited : and yet that there is a well-defined likeness between them ; that both have been created on a plan so strictly uniform, that the one and the other natu- rally find their place in the same system of classifica- tion. As the science of Palasontology progressed, and new DISTRIBUTION OF FOSSIL REMAINS. 2 13 facts were day by day accumulated, another truth, not less important, was gradually but certainly de- veloped. In the distribution of Fossil Kemains through the various strata of the Earth, there is a certain order observed, a certain regular law of succession, which cannot have been the mere result of chance, and which it is the business of science to unravel and explain. The facts are these. If we follow a particular set of strata in a horizontal direction, we find that the same fossils continue to prevail over hundreds of square miles, nay, often over a space as large as Europe, though beyond certain limits this uniformity of Fossil Remains will gradually be observed to disappear. But when we penetrate in a vertical direction through the strata, the forms of animal and vegetable life that we meet with are constantly changing. After a few hundred yards at the most, we find ourselves in the midst of a group of fossils, altogether difierent from those which we have passed in the beds above : and so on, as we proceed downwards, each particular set of strata is found to have an assemblage 0/ fossils peculiar to itself.^ There can be no reasonable doubt as to the truth of these facts. They have been established and confirmed by the positive testimony of a whole host of Geologists, whose researches have extended to all parts of the globe. And we have besides a kind of negative evi- dence on the subject which is scarcely less convincing than the positive. Nothing is more easy than to refute 1 See Lyell, Elements of Geology, pp. 94-96 ; PrinoipleB of Geology, p. 1 16 ; Jukes, Manual of Geology, pp. 410, 411. 214 SUCCESSION OF ORGANIC LIFE a universal proposition if it is false. If it is not a fact that each group of strata, as we proceed downwards, ex- hibits a collection of Fossils peculiar to itself, the asser- tion may be at once disproved by pointing out two or three different groups with the same Fossils. There are thousands of practical Geologists at work all over the world, eager for fame ; and any one of them would make his name illustrious if he could overturn a theory so generally received. Now, when a statement of facts can be easily disproved if untrue ; and when, at the same time, there is a large number of men whose inte- rest it would be to disprove the statement if possible ; and when it is nevertheless not disproved ; this circum- stance, we contend, is a convincing argument that the alleged facts are true. And such precisely is the case before us. We therefore think it would be unreason- able not to accept the facts. Let us next examine what is their significance. Each group of strata, be it remembered, represents to us the animal life that flourished on the Earth during the period in which that particular group was in progress of forma- tion. It is, as it were, a cabinet in which are preserved for our instruction certain relics or memorials of that age in the world's history. Of course it is not a perfect col- lection ; but only a collection of those remains that chanced to escape destruction, and by some natural em- balming process to be saved from dissolution. When we learn, then, that there is a marked uniformity in the assemblage of Fossils that are spread over a large hori- zontal area, in any group of strata, we conclude that. PROVED BY FOSSIL REMAINS. 2 1 5 when that group was in course of formation, there was a certain uniformity in the animal life that extended over the corresponding area of the globe ; just as, at the present day, the same species of animals are found to flourish over a great part of Europe, or of America. And if this uniformity of Fossil Kemains does not ex- tend horizontally to an indefinite distance, this is pre- cisely what we should have expected from the analogy of the existing creation: for when we examine the pre- sent distribution of animal life over the earth, we find a marked diversity to exist between countries that are far removed from one another, as, for instance, between Europe and Australia. In the next place, we are told that, as we pro- ceed downwards into the Crust of the Earth, each successive group of strata has an assemblage of Fossils clearly distinct in character from those of the group above and of the group below. The conclusion to which this fact points is obvious enough. If, in the former case, we inferred that the animal life of any one period, considered in itself, was the same over extensive areas, in this case we must infer that the animal life of each successive period -w&s peculiar to that particular age ; being altogether distinct in its character from the animal life of the period that went before and of the period that followed. It would appear, therefore, as Sir Charles Lyell puts it, " that from the remotest period there has been ever a coming in of new organic forms, and an ex- tinction of those which pre-existed on the earth ; some 2l6 GEOLOGICAL TIME NOT BECKONED species having endured for a longer, others for a shorter time ; while none have ever reappeared after once dying out.'" Now, from these principles, Geologists have been gradually led to build up a system of Geological Chro- nology ; in other words, to determine the order of time in which the numerous groups of strata that make up the Crust of the Earth have been fornied, and thus to fix the age of each group in reference to the rest. This Chronplogy is not reckoned by the common measures of time which are used in history, but rather by the suc- cessive periods during which each group of rocka was in its turn slowly deposited on the existing surface of the globe. For example, the Coal-measures that so abound in the North of England are very much older than the blueish clay on which London is built. But if we ask what is the difference between the age of the one and of the other, the answer is given not in days and years and centijries, but in the number of different Formations that intervened between the two. We are told that the Coal-measures belong to the Carboniferous Formation ; that this Formation was followed by the Permian, and that again in succession by the Triassic, the Jurassic, and the Cretaceous ; and that, upon this last was spread out the Eocene, to which the London clay belongs. Indeed, as regards the precise length of any given period, Geologists can offer nothing but the wildest con- ' Elements of Geology, p. 95. IN YEARS AND CENTURIES. 217 jectures. Some form their estimates in thousands of years ; others in millions. And the wisest amongst them fairly confess they have no sufficient data to make an accurate computation. Nevertheless, they are all agreed in this, that the ages of which the memory is preserved in history, that is to say, the last six thousand years, are but a small part of one Geological period. Compared to the voluminous chronicles laid up in the Crust of the Earth, the records inscribed by human hands constitute but an insignificant fraction of the world's history. Our readers will be glad to learn something of the way in which this startling system of Geological Chronology is constructed and developed. At first sight, perhaps, it might be imagined that the order of time in which the various strata were deposited, can be easily learned from the relative position in which they lie. Since each stratum, when first produced, was spread out on the existing surface of the globe, it is clear that the one which lies uppermost in the series must be the newest, then that which lies next below, and so on tUl we reach the lowest of the pile, which must be the oldest of all. Nothing could be more satisfactory than this reasoning, if each stratum was spread out over the whole Earth, and if, after having been once deposited, it was never afterwards removed. We might then re- gard each stratum as a volume in the Natural History of th^ Globe, which, when it was finished, was laid down upon that which contained the chronicles of the preced- ing age ; and thus the position of every stratum would 2 1 8 PRINCIPLES OF GEOLOGICAL CHRONOLOGY. be in itself a sufficient evidence of the age to which it belonged. But such is not the case. Nowhere does the Crust of the Earth exhibit a complete series of the Stratified Rocks laid out one above another. In any given section we can find but a few only of the long series of groups that are familiar to Geologists. And if we follow them on, in a horizontal direction, we shall invariably find that some of the strata will thin out and disappear, while new strata will gradually be developed between two groups that were before in immediate contact. Let it be observed, in passing, that this, fact fits in most per- fectly with the theory we have been all along defending. The Stratified Rocks were deposited under water ; there- fore, the strata of any given period were not spread out over the whole Globe, but at most over those parts only which, for the time, were submerged. With the next period came a change in the boundaries of land and water ; and the formation of strata ceased in some lo- calities and began in others : and so on from epoch to epoch. Thus the areas over which the process has been going on, have been, in every age, of limited extent, and have been ever shifting from place to place over the surface of the earth. Moreover, there is the oppo- site process of Denudation. Many of the strata depo- sited in the depths of the ocean must have been after- wards swept away by the breakers, as they slowly emerged from the waters ; or at a later time, reduced to their original elements, and carried back to the sea, by PRINCIPLES OF GEOLOGICAL CHRONOLOGY. 219 the action of rivers, rain, and frost. It should seem, therefore, as well from the fact which is obvious to any one who will examine it, as from our theory, which har- monizes so completely with the fact, that the strata which we meet with in any given section of the Earth's Crust present to us but a very broken and imperfect series of monuments. They are, as it were, but odd volumes of a long series, and, though they lie in juxta- position, they may belong, nevertheless, to Geological epochs widely removed from each other. Hence in order to construct a complete system of Geological Chronology it is necessary to collect toge- ther these odd volumes, as they may be called, of the great Geological Calendar, and to assign to each one its proper place in the series. This difficult and compli- cated task is accomplished chiefly by the aid of Fossil Kemains. We have already shown that the Fossil Ke- mains which are found imbedded in each group of strata, represent the organic life of the period during which that group of strata was in progress of formation. Moreover, we have seen that each period was marked by the existence of an animal and vegetable creation pecu- liar to itself. If, therefore, we find that the Fossils of two different districts exhibit the same general character, we may conclude that the beds in which they are pre- served were deposited about the same age, and conse- quently belong to the same Geological Period. Where- as, on the other hand, if, within certain limits, we discover two groups of strata, each of which has a col- lection of Fossils totally different from the other, it is 220 PRINCIPLES OF GEOLOGICAL CHRONOLOGY. a proof that these two groups were not deposited in the same ago, and must, consequently be referred to different Epochs of the Geological Calendar. Let us now see in what manner the practical Geologist proceeds to apply these general principles. He takes first some one country, say England, and in that country he selects some one particular district to begin with. Here he examines a number of different sections, and makes himself familiar with all the strata of the neighbourhood, and with the order in which they lie. Let us suppose that he finds three different groups spread out one above another, and let us call these groups A, B, and C ; A being the lowest, B imme- diately above A, and C above B. The chronological order of these strata will be, therefore, A, B, C. He will study next the Fossil Remains which he finds imbedded in each group. For convenience we may designate the Fossils of A by the letter a, those of B by b, and those of C by c. Now, according to the principles above ex- plained, these three collections of Fossils will be specifi- cally distinct from one another, each collection being characteristic of one particular set of strata. Our Geo- logist next goes into a neighbouring district, and there examines a number of sections as before. Let us sup- pose that he encounters again the groups A and B. He may, perhaps, have been able to trace the beds from one district to the other, by observations made upon his line of route : or it may be that the nature of the coun- try has rendered such observations impossible ; or the observations may have been so imperfe6t that from them PRINCIPLES OF GEOLOGICAL CHEONOLOGY. 221 he could arrive at no certain conclusion regarding the identity of the strata. But, at all events, if the new dis- trict yield an abundant supply of Fossils, he cannot long be at a loss. He will recognize the group A by the Fossils a, and the group B by the Fossils b. An impor- tant fact, however, soon attracts his attention. Group C has entirely disappeared, and is not to be found in this district ; while between A and B there is a new group of rocks that he has not seen before, with a collection of Fossils different from a, b, and c. We will call this new group X, and its Fossils x. It is clear that the forma- tion of X must have intervened between the formation of A and B ; and the chronological order now stands A, X, B, C. In like manner another district may dis- close a fourth group of strata, say Y, intervening be- tween B and C. The chronological order will then stand A, X, B, Y, C. And thus the Geologist pursues his explorations until he has gone through the whole country, and arranged the principal groups of strata ac- cording to the order of time in which they were depo- sited. In this way the whole of England has been minutely explored during the last half century. The task was first undertaken by William Smith, who is justly called the Father of English Geology. After multiplied re- searches extending over a space of many years, during which he travelled the whole country on foot, this emi- nent man published in. 1 8 1 5 his Geological Map of Eng- land and Wales with part of Scotland ; a work which is described by Sir Charles Lyell as " a lasting monument 222 PBINCIPLES OF GEOLOGICAL CHRONOLOGY. of original talent and extraordinary perseverance. Jlun- dreds followed in the same course, exploring every day new districts, and, by the new facts which they brought to light, supplying what was wanting in the work of Smith, correcting what was faulty, and confirming what was true ; until at length, in our day, it may be said that the Stratified Rocks of England are almost as well known and as completely mapped out as are its counties and its towns, its rivers, lakes, and mountains. Meanwhile, Geologists were not idle in other parts of the world. Germany, France, Italy, even many dis- tricts of America and Australia, have been diligently ex- plored according to the same principles as England. And by a comparison of the observations made, the Chronological order of strata over a considerable part of the Earth, but more particularly of Europe, has been now pretty fairly ascertained. This order we have at- tempted to set forth in an intelligible and sensible form by means of the table here annexed. In the Woodcut are represented the strata hitherto examined by Geologists, laid out one above another, ac- cording to the order of time in which they are supposed to have been produced. The whole series is divided into a number of Formations, the names of which are given in the first column, together with an approximate estimate of their thickness, in feet. These Formations are distinguished from each other in the drawing by a difierence of shading. Each one of them, according to Geological theory, is believed to have come into exis- tence by the accumulation of solid matter at the bottom TABLE OF STRATIFIED EOCKS, CHEONOtOQICALLr ASEANGBD. CRBTAOEOTJS. 12,000 00 o 000000 000 CHALK 0000 000000 000 224 TABLE OF STRATA EXPLAINED. of the sea ; and the Period of time occupied in its pro- duction is usually designated by the same name as the Formation itself. Thus we read of the Carboniferous Formation and the Carboniferous Period : by the former phrase is meant certain groups of strata contempo- raneously deposited over various parts of the Earth's surface ; and by the latter, the Period of time during which these groups of strata were spread out. In like manner, when we hear of the Carboniferous Fauna and Flora, we are to understand the animal and vegetable life that flourished during the Carboniferous Period. And again, when Geologists talk of the Cretaceous sea, and tell us that it rolled over a great part of what is now called Europe, they mean to speak of that sea on the bottom of which the Cretaceous rocks were deposited. Most of the Formations comprise various groups of strata ; and these groups are made up of different varieties of rocks, which are again divided into layers or beds of varying thickness. Even in these beds themselves we can often distinguish an indefinite num- ber of laminae or plates, scarcely thicker than a sheet of paper, which correspond to the periodical depositions of matter by which the rock was originally formed. These numerous subdivisions may be conveniently illustrated from the Carboniferous Formation. It is divided into two leading groups of strata ; the Mountain Limestone below, the Coal Measures above. The upper group is the larger as well as the more important. It attains a maximum thickness in South Wales of 12,000 feet ; and fionsi&ts of numerous strata of Sandstone and Shale, with TABLE OF STRATA EXPLAINED. 22$ thin seams of Coal occasionally interposed. In one remarkable instance a hundred distinct layers of Coal, varying in thickness from six inches to ten feet, have been counted in the one Coal-field, each resting on a bed of Shale, called in mining phraseology the Under- clay. This Shale itself naturally divides into an indefi- nite number of thin plates, just like the stratum of mud accumulated by the annual inundations of the river Nile, and constituting the present soil of Egypt. We have not attempted to represent in our Wood- cut these various divisions and subdivisions of Stratified Rocks. But the names of some important 2nd well- known groups we have had engraved, to impress more vividly on the mind the place to which they are to be referred in the Geological Calendar. Thus the reader may see at a glance the respective ages of the Coal and the Chalk ; of the Lias, in which are preserved the remains of extinct gigantic reptiles, and the Glacial Drift, in which the elephant, the rhinoceros, and the hippopotamus are found entombed ; of the Mountain Limestone, which is often nothing else than vast beds of Coral uplifted from beneath the waters of the ocean, and the Oolite which includes the Portland quarries where the petrified stems of ancient forest trees are found standing erect in the solid rock. As the series of Stratified Eocks is divided by Geolo- gists into a certain number of systems or Formations, so these are again grouped into still larger classes, called Primary, Secondary, and Tertiary ; that is to say, first, second,., and third, in the order of formation. These Q 2 26 TABLE OF STRATA EXPLAINED. larger classes correspond to the Great Epochs or Ages of Geological time, each comprising within itself many distinct Periods. The Primary rocks are also called Palse- ozic — TToXaiov, ancient, and ^oiov, an organic being — be- cause they contain the oldest forms of organic life : in like manner the term Mesozoic — fiiaov, middle, and ^wov — is applied to the Secondary strata, inasmuch as they contain the middle or intermediate forms of organic life : and the name Kainozoic — Kaivov, new, and gwov — is given to the Tertiary, which .'contain the newest forms of organic life. The term Post-Tertiary has recently been adopted to designate those superficial deposits which are subse- quent to the Tertiary Age. They are divided into two groups ; the Recent, which corresponds with the period of history, and the Post-Pliocene which precedes it. Some writers seem to think that these deposits, being so very insignificant and so very modem when compared with the long series of Stratified Kocks, are not truly Geological. But this, we should say, is a mistaken view of the question. It seems to us that even the minute layer of mud that is deposited every day at the mouth of the Ganges or the Mississippi, is linked on to the long chain of events which have brought the Crust of the Earth into its present condition ; and, therefore, truly belongs to the science of Geology, and is deserving of its proper place in Geological classification. We may here observe that the names of the great Geological Epochs are descriptive names ; that is to say, the obvious meaning of the words corresponds to the TABLE OF STRATA EXPLAINED. 227 ■ character of the strata they are used to represent. Pri- mary, Secondary, Tertiary, mean First, Second, and Third, in the order of formation : Palaeozoic, Mesozoic, and Kainozoic, signify that the strata so called are cha- racterized by Ancient, Middle, and Modern, forms of organic life. But it is very often quite otherwise with the names of the several Formations : and this is a point of no small importance to the student of Geology. These names must be regarded simply as names employed to designate the strata formed in each successive period, and not exactly to describe their character. They gene- rally had their origin in some accidental circumstance, or were derived from some particular locality ; and after- wards, being perpetuated, gradually came to receive a much more extended application than that which the words themselves would seem to suggest. Thus, for instance, the Cretaceous Formation is so called from the remarkable stratum of white chalk (creta) which was deposited during that period over a great part of Europe ; but it would be a mistake to suppose that the whole Formation is made up of chalk. On th« contrary, in different localities it is composed of very different mate- rials ; near Dresden, for example, it is a gray quartzose sandstone, and in many parts of the Alps it is a hard compact limestone.' Again, the Devonian Formation derives its name from Devonshire, where the rocks of the Devonian period were first minutely examined ; but we must not therefore infer that this Formation is pecu- ' Lyell, Principles of Geology, vol. i., p. iij. Q 3 228 TABLE OF STRATA EXPLAINED. liar to the county of Devon ; it is to be found in many- other parts of England, also in Ireland, and on the con- tinent of Europe. So, too, another Formation has re- ceived the name of Carboniferous, which literally means Coal-bearing (carbo fero) because of the beds of Coal which are sometimes associated with its strata ; yet this Formation is often found quite destitute of Coal over a very extensive area. In looking over our Table of strata the reader must have noticed that the successive spaces in the Woodcut are not proportioned to the actual thickness of the suc- cessive Formations for which they stand. The Secon- dary and Tertiary Rocks taken together are scarcely one-third as thick, in reality, as the Primary ; yet they occupy an equal space in the engraving : and, more re- markable still, the Cretaceous system is allowed double the space of the Laurentian though less than half as thick. This circumstance calls for a passing word of explanation. In the early annals of a country there is generally a great scarcity of authentic records ; and, from a simple dearth of facts, the history of a whole century is compressed, not unfrequently, into a few pages : whereas, in later times, when documentary evidence begins to accumulate, the historian will often spread out the events of two or three years over several chapters. Something of the same kind takes place in Geology. The Fossil Eemains, from which, as from authentic documents, the Geologist chiefly de- rives his information regarding the history of the Earth's Crust, are scanty in the earlier Formations, TABLE OF STRATA EXPLAINED. 229 and abundant in the more recent. And thus it hap- pens that the older Geological Periods, notwithstand- ing the vast thickness of the rocks by which they are represented, do not occupy a very prominent position in the annals of Geology, and are compressed into a comparatively insignificant space in its Tables. Never- theless the immense depth of the earliest Stratified Rocks must be taken into account in any attempt to estimate the comparative duration of the several Geological Periods. We have, therefore, set down, under the name of each Formation, an approxi- mate estimate of its actual thickness, taken chiefly from the works of Doctor Haughton and Sir Charles Lyell. Before bringing this chapter to an end we would observe that the system of classification we have here endeavoured to explain does not pretend to be final and complete. It is, on the contrary, little more than a temporary expedient to render intelli- gible the results at which Geologists have hitherto arrived ; and is liable to manifold modifications in proportion as their acquaintance with the records they have undertaken to interpret becomes more extensive and more minute. All that they now contend for is this : that the successive Formations represent succes- sive Periods of time, which followed one another in the order here set forth, and during which the Earth was peopled with certain species of Plants and Ani- mals, for the most part peculiar to their respective eras.' ' Lyell, Elements of Geology, p. loo. CHAPTER XIII. GEOLOGICAL CHRONOLOGY — REMARKS ON THE SUCCES- SION OF ORGANIC LIFE. SCMMAET or THE HISTORY OP STRATIFIED ROCKS — STRIKINQ CHA- RACTERISTICS OP CERTAIN PORMATIONS — HUMAN REMAINS POUND ONLY IN SUPERFICIAL DEPOSITS — ORADUAl TRANSITION FROM THE ORGANIC LIFE OP ONE PERIOD TO THAT OP THE NEXT — EVIDENCE IN FAVOUR OF THIS OPINION — ADVANCE PROM LOWER TO HIGHER TYPES OF OSGANIC LIFE AS WE ASCEND FROM THE OLDER TO THE MORE RECENT PORMATIONS — ECONOMIC VALUE OP GEOLOGICAL CHRONO- LOGY — ILLUSTRATION— SEARCH FOR COAL THE PRACTICAL MAN AT FAULT — THE GEOLOGIST COMES TO HIS AID, AND SAVES HIM PROM USELESS EXPENSE. With this sketch of Geological Chronology before us, we can now more fully realize to our minds the story we are told about the formation of the Earth's Crust. In the earliest age to which Geologists can trace back the history of the Aqueous Rocks — for they do not pro- fess to trace it back to the beginning — this Globe of ours was, as it is now, partly covered with water, and partly dry land. The formation of stratified rocks went on in that age, as it is still going on, chiefly over those areas that were under water — not indeed throughout the en- tire extent of such areas, but over certain portions of them to which mineral matter happened to be carried by the action of natural causes. And the Earth was peopled then as now, though with animals and plants very different? from those by which we are surrounded HISTORY OF THE STRATIFIED ROOKS. 23 I at the present day. Some of these happened to escape destruction, and to be imbedded in the deposits of that far distant age, and have thus been preserved even to our time. And these strata with their Fossils are the same that we now group together under the title of the Laurentian Formation : whichbeing the oldest group of stratified rocks we can recognize in the depths of the Earth's Crust, occupies the lowest position in our table of Chronology. Ages rolled on ; and the Crust of the Earth was moved from within by some giant force, the bed of the ocean was lifted up in one place, islands and continents were submerged in another, and so the outlines of land and water were changed. With this change the old forms of life passed away ; a new creation came in ; and the Laurentian period gave place to the Cambrian. But the order of nature was still the same as before. The deposition of stratified rocks still continued, though the areas of deposition were, in many cases, shifted from one locality to another. And the organic life that flourished in the Cambrian times left its memorials behind it buried in the Cambrian rocks. Then that age, too, came to an end, and gave place in its turn to the Silurian : and this was, again, followed by the Devonian. Thus one period succeeded to another in the order set forth in our table ; and every part of the globe was, in the course of ages, more than once submerged, and covered with the deposits of more than one age, and enriched with the Organic Remains of more than one creation. As we advance upwards in the series of Formations 232 ANCIENT INHABITANTS OF THE EARTH. we soon perceive that the Fossil Eemaing, which in the earlier groups were scanty enough, become profusely abundant, until even the unpractised eye cannot fail to mark the peculiar character of each successive period ; — the exuberant vegetation of the Carboniferous, with its luxuriant herbage and its tangled forests, its huge pines, its tall tree-ferns, and its stately araucarias ; the enor- mous creeping monsters of the Jurassic, the ichthyosaurs, the megalosaurs, the iguanodons, which filled its seas or crowded its plains or haunted its rivers ; and higher up in the scale, the colossal quadrupeds of the Miocene and the Pliocene, the mammoths, the mastodons, the megatheriums, which begin to approximate more closely to the organic types of our own age. But amidst these various forms of life, the eye looks in vain for any relic of human kind. No bone of man, no trace of human intelligence, is to be found in any bed of rock that be- longs to the Primary, Secondary, or Tertiary Forma- tions. It is only when we have passed all these, and come to the latest Formation of the whole series, nay, it is only in the uppermost beds of this Formation, that we meet, for the first time, with human bones, and the works of human art. Thus it appears pretty plain, even from the testimony of Geology, that man was the last work of the creation ; and that, if the world is old, the human race is compa- ratively young. These broken and imperfect records, which have been so curiously preserved in the Crust of the Earth, carry us back to an antiquity which may not be measured by years and centuries, and then set before MAN THE LAST WORK OF CREATION. 233 US, as in a palpable form, how the tender herbage ap- peared, and the fruit tree yielding fruit according to its kind ; and how the Earth was afterwards peopled with great creeping things, and winged fowl, and the cattle, and the beasts of the field ; and then, at length, they disclose to us how, last of all, man appeared, to whom all these things seem to tend, and who was to have do- minion over the fish of the sea, and the fowl of the air, and every living thing that moveth upon the earth. We do not mean to dwell just now upon this view of the his- tory of creation so clearly displayed in the records of Geology. But we shall return to it hereafter when we come in the sequel to consider how admirably the genuine truths of this science fit in with the inspired narrative of Moses. It may here, very naturally, be asked, if the records of Geology give us any information as to the manner in which each period of animal and vegetable life was brought to an end ? Did the old organic forms gradu- ally die out, and the new gradually come in to take their places ? or were the one suddenly extinguished, and the others as suddenly produced ? This question has been a subject of controversy among Geologists themselves ; and therefore it is somewhat outside our scope, since we propose to exhibit only that more general outline of Geological theory which is accepted by all. Neverthe- less, as it is a question that must needs occur to the mind of every reader, it seems to call for a few words of ex- planation as we pass along. In the early days of Geo- logy, it was commonly held that each great period was 234 EXTINCTION AND INTRODUCTION OF SPECIES brought to an end by a sudden and violent convulsion of Nature. The Crust of the Earth was burst open in many places all at once ; the bottom of the ocean was upheaved with a tremendous shock ; the waters, driven from their accustomed bed, rushed with furious impe- tuosity over islands and continents ; and the whole ex- isting creation perished in a universal deluge. Then succeeded an interval of chaotic confusion, and when at length the waters subsided, and dry land again appeared, a new age in the history of the Globe was ushered in, and the Earth was again peopled by a new creation. But this old theory has gradually given way as the Stratified Eocks have been more and more fully ex- . amined, and at the present day it is almost universally abandoned. Geologists have observed that the same species of Fossil Remains which prevail in the upper beds of one Formation, are met with also in the lower beds of the next, though in less numbers and mixed up with new species ; and that, as we ascend higher and higher into the later Formation, the old species gradually become more and more scarce, while the new gradually become more and more numerous ; until at length the characteristic forms of one age have disappeared alto- gether, and those of the succeeding age have attained their full development. For this important fact, which was brought to light within the last half century, we are mainly indebted to the unwearied researches and great ability of Sir Charles Lyell. Speaking of the Formations of the Tertiary Epoch, to which, as is well known, he has principally NOT SUDDEN, BUT GRADUAL. 235 devoted himself, this distinguished writer thus sums up the result of his long investigation : — " In passing from the older to the newer members of the Tertiary system we meet with many chasms, but none which separate entirely, by a broad line of demarcation, one state of the organic world from another. There are no signs of an abrupt termination of one fauna and flora, and the start- ing into life of new and wholly distinct forms. Although we are far from being able to demonstrate geologically an insensible transition from the Eocene to the Miocene, or even from the latter to the recent fauna, yet the more we enlarge and perfect our general survey, the more nearly do we approximate to such a continuous series, and the more gradually are we conducted from times when many of the genera and nearly all the species were extinct, to those in which scarcely a single species flourished which we do not know to exist at present."' Hence he concludes, and his conclusion is now the common doctrine of Geologists, that the extinction and creation of species has been " the result of a slow and gradual change in the organic world."^ It was long argued against this view, that we often meet, especially in the Primary and Secondary Forma- tions, two groups of strata in immediate contact, in which there is a perfectly sudden transition from one set of Fossil Remains to another altogether different. Each group contains a countless variety of species, and yet there is not a single species common to the two. Does ' Principles of Geology, vol. i., p. 3"- ' lb- 3 '3- 236 STRATA IN IMMEDIATE CONTACT it not appear that in such a case the organic life of one period was suddenly destroyed, and that of the next as suddenly introduced ? Not so ; there is one link want- ing in the argument. It must be shown that these two strata which are now in immediate contact were originally deposited in immediate succession. But this it is impossible to prove : nay, it must needs be very often false. We have before observed that the areas of deposition were limited in every age, and were ever shifting from one locality to another. Therefore it must have been a fre- quent occurrence that, after one bed of rock was formed, the process of deposition ceased altogether in that loca- lity and did not begin again for many ages. Thus along lapse of time often intervened between the deposition of two strata, which were laid out one immediately above the other. Furthermore, we have also seen that whole groups of strata may in any age be swept away by De- nudation ; and then the rocks which are next deposited in that locality, will be in immediate contact with strata indefinitely more ancient than themselves. From these considerations it is plain that two groups of strata which which are now found in juxtaposition, may have been deposited in two Geological ages widely remote from each other. And consequently a sudden transition from the Organic Life of one group to the Organic Life of the other affords no proof of a sudden transition from the Organic Life of one Geological Period to the Organic Life of that which next succeeded. We may observe, however, that the recent researches, which have contri- buted so much to fill up the interstices of the Geological NOT ALWAYS DEPOSITED IN IMMEDIATE SUCCESSION. 237 Calendar, have conduced in no small degree to fill up likewise some of the more remarkable gaps or chasms in the succession of Organic Life. It is, therefore, not unreasonable to suppose that, as our knowledge of the Earth's Crust becomes more and more minute, the sud- den breaks in the continuity of the scale will be still fur- ther diminished and the successive stages of gradual transition will be made more clearly apparent. This subject has been very happily illustrated by Sir Charles Lyell : — " To make still more clear the supposed working of this machinery, [for the deposition of Stra- tified Kocks and the preservation of Organic Kemains,] I shall compare it to a somewhat analogous case that might be imagined to occur in the history of human affairs. Let the mortality of the population of a large country represent the successive extinction of species, and the birth of new individuals the introduction of new species. While these fluctuations are gradually taking place everywhere, suppose commissioners to be appointed to visit each province of the country in succession, tak- ing an exact account of the number, names, and indivi- dual peculiarities of all the inhabitants, and leaving in each district a register containing a record of this infor- mation. If, after the completion of one census, another is immediately made on the same plan, and then another, there will, at last, be a series of statistical documents in each province. When these belonging to any one pro- vince are arranged in chronological order, the contents of such as stand next to each other wiU differ according to the length of time between the taking of each census. 238 ILLUSTRATION OF SIR CHARLES LYELL. If, for example, there are sixty provinces, and all the registers are made in a single year, and renewed annu- ally, the number of births and deaths will be so small in proportion to the whole of the inhabitants, during the interval between the compiling of two consecutive docu- ments, that the individuals described in such documents will be nearly identical ; whereas, if the survey of each of the sixty provinces occupies all the commissioners for a whole year, so that they are unable to revisit the same place until the expiration of sixty years, there will then be an almost entire discordance between the persons enumerated in two consecutive registers in the same province. " But I must remind the reader, that the case above proposed has no pretentions to be regarded as an exact parallel to the Geological phenomena which I desire to illustrate ; for the commissioners are supposed to visit the different provinces in rotation ; whereas the com- memorating processes by which organic remains become fossilised, although they -are always shifting from one area to the other, are yet very irregular in their move- ments. They may abandon and revisit many spaces again and again, before they once approach another dis- trict; and besides this source of irregularity, it may often happen that, while the depositing process is sus- pended, Denudation may take place, which may be com- pared to the occasional destruction by fire or other causes of some of the statistical documents before men- tioned. It is evident that, where such accidents occur, the want of continuity in the series may become indefi- ASCENDING SCALE OF ANIMAL LIFE. 239 nitely great, and that the monuments which follow next in succession will by no means be equi-distant from each other in point of time. "If this train of reasoning be admitted, the occasional distinctness of the fossil remains, in formations imme- diately in contact, would be a necessary consequence of the existing laws of sedimentary deposition and subter- ranean movement, accompanied by a constant mortality and renovation of species."' There is another and a very striking fact in the succes- sion of ancient organic life, which claims from us a mo- ment's notice. As we proceed upwards through the series of Stratified Rocks, from the oldest to the newest, we find a gradual advance La the types of animal orga- nization therein preserved, from the humbler and more simple forms of structure to those of a higher and more perfect character. That form of organization is regarded among Zoologists as the more perfect in which there is " a greater number of organs specially devoted to parti- cular functions." Now all the forms of animal life with which we are acquainted may be reduced to two great divisions, the Vertebrate and the Invertebrate,— the former having a vertebral or spinal column, the latter having none : and it is agreed in conformity with the notion set forth above, that the Vertebrate animals as a class exhibit a more perfect organization than the Inver- tebrate. Again among the Vertebrate themselves there is a gradation ; the Eeptiles are ranked higher than the ' Principles of Geology, vol. i., pp. 321, 322. 240 ADVANCE FKOM LOWER TO HIGHER FORMS OF LIFE. Fish, the Birds higher thaa the Reptiles, and the Mam- malia higher again than the Birds. All this we learn from Zoologists, who have pursued their investigations without any reference whatever to the science of Geology. It is, therefore, not a little re- markable that we should discover this very order and gradation of animal life in the successive groups of Stratified Rocks. All the Remains hitherto discovered in the earliest Geological Formations belong to Inverte- brate animals, while the Vertebrate, which appear for the first time in the later part of the Silurian Period, are, from that age on, more and more fully developed down to the present day, and now constitute, if not the most numerous, at least the most important part of the animal creation. Moreover, it is to be observed that the Vertebrate animals do not all make their appearance at once, but come in successively according to the same scale of organic perfection, — the Fish appearing first, then the Reptiles, then the Birds, and lastly the Mam- malia. Even among the Mammalia a well defined or- der of progressive succession has been observed, which finally culminates in the appearance of Man, the last created and the most perfect of animals. This remarkable succession of animal life in the his- tory of the Earth's Crust will be more readily understood by means of the annexed Table. The remains of Inver- tebrate animals have been traced as far back as the Lower Laurentian Rocks. The Vertebrate first become manifest in the Ludlow beds of the Upper Silurian; where they are represented by the bones of Fish, the TABLE OF GEOLOGICAL FORMATIONS, SHOWING THE FIRST APPEARANCE ON THE EARTH OF THE VARIOUS FORMS OF ANIMAL LIFE. Gigantic Mamma- lian quadrupeds now extinct. oo o oooooo o o o CHALK o o o o ooo ooo ooo CRSTACEOUS. Shells of minute ani- malcules compoaing tlie White Chalk. Extraordinaiy develop- ment of marine Reptiles, Oldest Foml Mammal. Earliest trace of Birds. Z^MOUIMTAIN LIMESTONE^ --^~-nw ■ ^%rst appearance of Reptiles ; Ar- chegosawvx ,• discovered in the Coal Measures near Strasburg, 1847. Fossil Fish in great ahundance. Most ancient Fossil Fish ; found near Ludlow, on the borders of Hereford- sMre. Sozoon Canadense ; oldest knomi Fossil, 242 EXPLANATION OF THE TABLE. lowest class belonging to the Province of Vertebrates. Next in order come the Keptiles : the oldest known Reptile having been found in the Coal Measures of Saar- briick between Strasburg and Treves. The skeletons of Birds are rare in the Stratified Bocks. It is supposed that their powers of flight have in all ages secured them, to a great . extent, from being carried away by floods, like other land animals, and buried in the sedimentary deposits of rivers and estuaries. Nevertheless their presence in the ancient world is frequently attested by their footsteps, impressed originally on the sandy beach, and still preserved now that the soft sand has been con- verted into solid rock. Such traces have been discovered in great abundance on the New Eed Sandstone of the Connecticut river, in America ; and afford the earliest evidence we possess in the records of Geology regard- ing the existence of the feathered tribe. This group of strata belongs to the lower Trias. In the higher beds of the same Formation we meet with the first relic of ancient Mammals. It was found near Stuttgardt, in 1 847, and belongs to the more imperfect form of Mam- malian life, the Non Placental. Similar remains have been since discovered in the Upper Trias of Somerset- shire. The Placental, or more perfect form of animal life in the same class, first appears in the Eocene Formation : and the bones of Man, the highest of the Placentals, are found for the first time in the upper deposits of the Post-Tertiary Age. Let it be remembered that we are here but stating the facts which have been hitherto brought to light by the EXPLANATION OF THE TABLE. 243 researches of Geologists. It may be, it is indeed most probable, that new discoveries will lead to numerous mo- difications in our Table. There is no reason to suppose that Geologists have yet exhumed the earliest remains of Vertebrates or Invertebrates preserved in the Crust of the Earth : that Fish may not hereafter be traced back beyond the Silurian, or Reptiles beyond the Car- boniferous Period : that Birds may not be found among the Primary Rocks, and Placentals among the Secondary. But in a science which depends mainly upon observation, it is better to register the facts we have than to speculate idly about those we have not. And, having registered them, we cannot fail to be struck with the succession of animal life on the Earth, to which they seem to point. It is certainly deserving of notice that, as far as the Organic Remains hitherto discovered may be taken as a guide, Invertebrates and Vertebrates, Fish, Reptiles, Birds, and Mammals, Non-Placentals and Placentals, follow one another in the ascending series of Geological Formations exactly in the same order as they follow one another in the ascending scale of Zoological Classification. And so Geologists go on ever searching out new phe- nomena, and grouping them together into classes, until from particular facts they lead us to general truths. Then starting with these general truths as the groundwork of their science, they proceed to sketch out the Natural History of our Globe from the remotest ages of the past down to the present time. They first study the stratified E 2 244 ECONOMIC VALUE OF GEOLOGY. deposits of each succeeding age, and analyze the Fossil Kemains imbedded therein ; afterwards they make their inferences, and they compile their history. They de- scribe the forms, the character, the habits, of the plants and animals that flourished of old in this world of ours ; they teU us where the deep sea rolled its waves in each succeeding age, and where the dry land appeared ; they point out the Deltas of its ancient rivers, they measure the breadth of its Estuaries, they trace the course of its Glaciers, they mark the outlines of its Mountain chains. But with these and such like speculations we are not here concerned. Many of them are open to controversy, and not a few are at this moment warmly disputed among Geologists themselves : besides, whether true or false, they do not in any way affect the relations be- tween Geology and Revealed Eeligion. We shall be quite content, and it is all that our present scope de- mands, if we have made intelligible the general theory of Geological Chronology, and the kind of evidence on which it rests. Before taking leave of this subject, however, we will venture to offer what seems to us an interesting illustra- tion of the principles we have been explaining in the last two chapters;— one that will help to confirm the conclusions for which we have been contending, and that will also bring home to many minds the practical advantage to be derived from a thorough knowledge and just application of Geological science. Perhaps, too, it may help to revive the flagging attention of our readers ; for the subject of our illustration is Coal and the way to SEARCH FOR COAL. 245 find it. In this age of manufactories and steam en- gines, — when the atmosphere of great towns is heavy with smoke, and the quiet solitude of the country is so rudely disturbed by the shrieking of the railway whistle and the snorting of the sooty locomotive, — this black, dirty, mineral has acquired a value and an importance, which may succeed in rousing even the practical money- making man to pay some heed to the lessons of science. Coal might have been producd in any Geological Period ; and in point of fact, beds of Coal have been discovered in many diflferent Formations. But in Eng- land, and in Western Europe generally, it has been found by long experience that the Coal-beds of the Carboniferous Formation are more abundant, and of better quality, than those of any other. Indeed the beds of Coal that occur in other Formations are so thin, and of such inferior quality, that they cannot be worked with profit. It is therefore of the highest importance in the search for Coal, before going to the enormous expense of sinking deep shafts, to discover whether or no the rocks in which the search is to be made belong to the Carboniferous Period. In this matter the mere practical man is often seriously at fault. Coal-bearing strata generally consist pretty largely of dark-coloured clay, black shales, and similar deposits. This is a fact which, as it strikes the eye, is perfectly famihar to all who are engaged in the working of Coal mines. Hence it happens, not unfrequently, that the practical man, when he meets with strata of this kind, is apt at once to infer that Coal is near at hand. The Geologist, on the 246 THE PRACTICAL MAN AT FAULT. contrary, knows well that such strata are not peculiar to the Carboniferous rocks, but are often found in other Formations in which there is no Coal at all, or at least no Coal that will repay the expense of working : and therefore he will pronounce it most rash to undertake costly works on the strength of these appearances. He has learned, however, that there are certain species of animals and plants which are found in the Carboniferous rocks and in them alone ; he will search for these in the strata which it is proposed to explore ; and by their presence or their absence he will know whether the strata in question belong to the Carboniferous Forma- tion or not. Again it will often happen that, in the midst of an extensive region well known to abound in Coal, the rocks which appear at the surface in one particular lo- cality, are not only wholly devoid of Coal, but exhibit no resemblance either in mineral character or in Fossil Eemains to the Coal-bearing strata. A question then arises of the highest practical importance. May it be that the Coal-bearing strata are spread out beneath this uppermost bed of rocks ? and is it worth the expense to sink a shaft through the one in the hope of reaching the other ? The practical miner has no very clear or cer- tain principles to help him in the solution of this prob- lem : and thus it has often happened that thousands upon thousands of pounds have been expended in sink- ing shafts to look for Coal, where, as it afterwards proved, there was not the slightest chance of finding it. Now, though Geology cannot tell if we shall succeed in USEFUL APPLICATION OF GEOLOGICAL CHRONOLOGY. 247 finding Coal beneath these rocks, it can tell if there is a good chance of succeeding. It can tell whether there is a reasonable hope, by penetrating into the Crust of the Earth at this particular spot, of reaching the Carboni- ferous Formation ; and if we can reach the Carboni- ferous Formation in the midst of a Coal district, it is very likely we shall meet with beds of Coal. His first object will be to ascertain what is the Forma- tion to which the superficial rocks belong. If it be a Formation earlier in date than the Carboniferous, — the Silurian, for instance, or the Devonian, — he knows that it would be simply waste of money to look for Coal beneath them ; because the Carboniferous rocks cannot possibly be found underneath the rocks of an earlier age. And so the Geologist can tell beforehand what the mere practical man would find out only when he had spent his money. If, on the other hand, the rocks which appear at the surface belong to a period later than the Carboniferous, the Geologist will not always conclude that it is expedient to sink a shaft in search of Coal. For though the Carboniferous rocks may, in this case, be underneath, they may be so far down in the Crust of the Earth that we should have no chance of ever reaching them. Suppose, for example, that the strata which appear at the surface belong to the Cre- taceous Formation. He knows from his Chronological table that the Carboniferous age is separated from the Cretaceous by three intermediate Periods, — the Per- mian, the Triassic, the Jurassic. Therefore, when he finds the Cretaceous rocks at the surface in any locality. 248 USEFUL APPLICATION OF GEOLOGICAL CHRONOLOGY. it is quite possible, though of course not certain, that before the Carboniferous Formation could be reached it would be necessary to bore through thousands of feet of Jurassic, Triassic, and Permian rocks. And even then there would be no certainty of meeting with the Coal-bearing strata. Perhaps they were never deposited over this area of the earth's surface ; or, if deposited, perhaps they were subsequently swept away by Denudation. Hence our Geologist would reasonably conclude that, the probable expense of the search being so enormous, and the chance of success so remote, it would be much wiser not to make the attempt. CHAPTEE XIV. SUBTERRANEAN HEAT — ITS EXISTENCE DEMONSTRATED BY FACTS. THEORY OP STRATIFIED ROCKS SUPPOSES DISTURBANCES OP THE earth's crust — THESE DISTURBANCES ASCRIBED BY &E0L00I8TS TO THE ACTION OP SUBTERRANEAN HEAT — THE EXISTENCE OP SUBTER- RANEAN HEAT, AND ITS POWER TO MOVE THE CRUST OP THE EARTH, PROVED BY DIRECT EVIDENCE— SUPPOSED lONEOUS ORIGIN OF OUR GLOBE REiLAREABLE INCREASE OP TEMPERATURE AS WE DESCEND INTO THE earth's crust — HOT SPRINGS — ARTESIAN WELLS— STEAM ISSUING PROM CREVICES IN THE EARTH THE GEYSERS OP ICELAND— A GLIMPSE AT THE SUBTERRANEAN PIRES — MOUNT VESUVIUS DJ I779 — VAST EXTENT OP VOLCANIC ACTION— EXISTENCE OP SUBTERRANEAN HEAT AN ESTABLISHED PACT. In developing the modern theory of Geology, we have all along assumed that the Crust of the Earth has been subject to frequent disturbances from the earliest ages of the world. Again and again, in the course of our argument, we have talked of the bed of the sea being lifted up, and converted into dry land ; and, on the other hand, of the dry land being submerged beneath the waters of the sea. We have not even hesitated to sup- pose that these two opposite movements of upheaval and submersion often took place by turns over the same area ; nay, that there is scarcely a region on the surface of the Globe which has not been several times submerged, and several times again upheaved. Yet all this has not been taken for granted without 250 DISTURBANCES OF THE EARTH'S CRUST. proof. Our readers have seen what a long array of sober reasoning may be drawn out to show that the Stratified Rocks have been, for the most part, deposited under water: — first, from the nature and arrangement of the materials which compose them ; secondly, from the cha- racter of the Organic Remains they contain. And since they are now above water, it is plain that either they have been lifted or the ocean has subsided. Further- more, if we find, as we often do, two strata in immediate succession, the one underneath, exhibiting the trees of an ancient forest still standing erect with their roots attached, the other above, abounding in the remains of aquatic animals ; we must conclude that when the ancient forest flourished this portion of the Earth's Crust was above the level of the sea ; that afterwards it was sub- merged, and a new deposit, in which the marine remains were imbedded, was spread out above the earlier vege- tation ; and that, last of all it again emerged from the waters, and became once more dry land. Finally, when a vertical section of the Earth's Crust exhibits a con- tinued series of such strata alternating with each other, it affords a proof that this particular area must have been several times under water, and several times again dry land, in the long course of ages. These conclusions are now all but universally re- ceived among Geologists. The Crust of the Earth, we are assured, is not that unyielding and immovable mass which men commonly take it to be. On the contrary, it has been from the beginning ever restless and in mo- tion, rising here and subsiding there, sometimes with a SUBTERRANEAN HEAT. 251 convulsive shock capable of upturning, twisting, dis- torting hard and stubborn rocks as if they were but flimsy layers of pliant clay ; sometimes with a gentle, undulating movement, which, while it uplifts islands and continents, leaves the general aspect of the surface unchanged, the arrangement of the strata undisturbed, and even the most tender Fossils unharmed. Disturb- ances of this kind have been going on in various parts of the world even within the period of history ; and they may be distinctly traced to the action of subterranean Heat. In support of a theory so startling and unex- pected, Geologists appeal to the direct evidence of facts : and we now propose to bring some of these facts under the notice of our readers. At the outset, however, it is important to set forth clearly the doctrine we hope to illustrate and to confirm. With the origin of the internal heat that prevails within the Crust of the Earth we have no concern. This is still an unsettled point among Geologists themselves. Some conjecture that our Globe, when first launched into space, was in a state of igneous fusion ; that is to say, that all the solid matter of which it is composed was held in a molten condition by the action of intense heat ; that, in course of time, as this heat passed off by radia- tion, the surface gradually cooled and grew hard ; that an external shell of solid rock was thus formed, which has been ever growing thicker in proportion as the Earth has been growing cooler ; and that the actual condition of our planet is the result of this process con- tinued down to the present day, — a fiery mass of seeth- 252 THE QUESTION STATED. ing mineral within, and a comparatively thin crust of consolidated rock without. Others suppose that the in- ternal heat of the Globe is developed by the agency of chemical changes constantly going on in the depths of the Earth ; and others, again, look for a cause to the action of electricity and magnetism. But these and such like speculations are still under discussion, and not one of them can be regarded as anything more, at best, than a satisfactory hypothesis. Any how, it is not about the causes of internal heat that we are just now interested, but about the fact of its existence, and the nature of its effects. Is it true that an intense heat prevails very generally beneath the superficial covering of the Globe ? and is that heat capable of producing those stupendous changes which are ascribed to it in our theory of Geo- logy ? These are the questions to which we mean to devote our chief attention. It is a very significant fact, that the deeper we penetrate into the Crust of the Earth, the hotter it is. At first, no doubt, for a short distance, the reverse is the case. When we begin to descend we find it cooler below than above, because the further we depart from the surface the more we are removed from the influence of the Sun. But at a certain point — in our climate at about fifty feet below the surface — the influence of the Sun's heat ceases to be sensibly felt. When this limit is passed, the tem- perature begins to rise, and thenceforth the deeper we go the hotter the earth becomes. This broad and general fact has been tested by expe- riments in every part of the world, and has been found EVIDENCE OF FACTS. 253 true in all countries, in all climates, in all latitudes, whether in coal-pits, or mines, or deep subterranean caves. " In one and the same mine," says Sir John Herschel,' " each particular depth has its own particular degree of heat, which never varies : but the lower al- ways the hotter; and that not by a'trifling, but what may well be called an astonishingly rapid rate of in- crease, — about a degree of the thermometer additional warmth for every ninety feet of additional depth,'' which is about 58° per mile ! — so that, if we had a shaft sunk a mile deep, we should find in the rock a heat of 105", which is much hotter than the hottest summer day ever experienced in England." Now if the temperature con- tinue to increase at this rate towards the centre of the Earth, it is quite certain that, at no very great distance from the surface, the heat would be sufficiently intense to reduce the hardest granite and the most refractory metals to a state of igneous fusion. Again, every one is familiar with the existence of hot springs, which come up from unknown depths in the Earth's Crust, and which, appearing as they do in al- most all parts of the world, testify in unmistakable lan- 1 Familiar Lectures on Scientific Subjects : London, 1867 ; pp. 9, 10. « It would be more strictly correct to say that the rate of increase va- ries considerably in different places, thougb the main fact is everywhere palpably apparent that the deeper we descend into the Earth the higher the temperature becomes. Sir Charles Lyell records a number of careful experiments made in England, Prance, Germany, and Italy, which seem to show that an increase of one degree Fahrenheit for every sixty-five feet of descent would represent pretty correctly the general average. See his Principles of Glology, vol. ii., pp. 205, 206. 254 HOT SPRINGS AND ARTESIAN WKLLS. guage to the existence of internal heat. At Bath, for instance, in England, the water comes up from the bowels of the Earth at a temperature of 117° Fahren- heit ; and in the United States, on the Arkansas River, there is a spring at 1 80° — not much below the boiling point. This remafkable phenomenon, however, may be more closely investigated in the case of Artesian Wells, so called from the province of Artois, in France, where they first came into use. These weUs are formed artifi- cially, by boring down through the superficial strata of the Earth, sometimes to enormous depths, until water is reached. It has been found in every case that the water coming up from these great depths is always hot ; and, furthermore, that the deeper the boring the hotter the water. A well of this kind was sunk in 1834 at Grenelle, in the suburbs of Paris, to a depth of more than 1 800 English feet, and the water, which rushed up with sur- prising force, had a temperature of 82° Fahrenheit ; whereas the mean temperature of the air in the cellars of the Paris Observatory is only 53°. The water has ever since continued to flow, and the temperature has never varied. At Salzwerth, in Germany, where the boring is stiU deeper, being 2,144 feet, the water which rises to the surface is 91° of our scale. Then we have, in many countries, jets of steam which issue at a high temperature from crevices in the Earth, and which tell of the existence of heated water below, as plainly as the steam that escapes from the funnel of a locomotive or from the spout of a tea-kettle. Pheno- mena of this kind are very common in Italy, where they GEYSERS OF ICELAND. 255 are sometimes exhibited at intervals along a line of country twenty miles in length. But in Iceland it is that they are displayed in the highest degree of splen- dour and power. On the south-west side of that island, within a circuit of two miles, there are nearly a hundred hot springs called Geysers, from sonie of which, at in- tervals, immense volumes of steam and boiling water are violently projected into the air. The Great Geyser is a natural tube, ten feet wide, descending into the Earth to a depth of seventy feet, and opening out above into a broad basin, from fifty to sixty feet in diameter. This basin, as well as the tube which connects it with the in- terior of the Earth, is lined with a beautifully smooth and hard plaster of siliceous cement, and is generally filled to the brim with water of a clear azure colour, and a temperature little below boiling point. The ordinary condition of the spring is one of comparative repose, the water rising slowly in the tube and trickling over the edge of the stony basin. But every few hours an eruption takes place. Subterranean explosions are first heard, like the firing of distant cannon ; then a violent ebullition follows, clouds of steam are given out, and jets of boiling water are cast up into the air. After a little the disturbance ceases, and all is quiet again. Once a day, or thereabouts, these phenomena are exhi- bited on a scale of extraordinary grandeur : the ex- plosions which announce beforehand the approaching display are more numerous and violent than usual ; then such volumes of steam rush forth as to obscure the at- mosphere for half a mile around ; and, finally, a vast 256 A GLIMPSE AT THE SUBTERRANEAN FIRES. column of water is projected to a height of from one to two hundred feet, and continues for a quaa;ter of an hour to play like an artificial fountain. Geysers scarcely less grand and striking are to be seen in New Zealand, from which the water is thrown up at a temperature 214° Fahrenheit, or two degrees above boiling point. Such are the evident symptoms of subterranean heat, — hot springs, jets of steam, fountains of boiling water, — which are manifested unceasingly at the surface of the Earth in every quarter of the Globe. But it is some- times given us to behold, as it were, the subterranean fire itself, and to contemplate its power under a more striking and awful form. From time to time, in the fury of its rage, the fiery element bursts asunder the prison house in which it is confined, and rushes forth into the light of day ; then flames are seen to issue from the surface of the Earth, yawning chasms begin to appear on every side, the roaring of the furnaces is heard in the depths below, clouds of red-hot cinders are ejected high into the air, and streams of incandescent liquid rock are poured forth from every crevice, which rolling far away through smiling fields and peaceful villages, carry de- struction and desolation in their track. These are the ordinary phenomena of an active Volcano during the period of eruption ; and, even while we write, most of them may be witnessed actually taking place, for the hundredth time, on the historic ground of Mount Vesu- vius. Our typical example, however, we shall take from the eruption of that mountain in the year 1779. It was not indeed especially remarkable for its violence or for ERUPTION OF MOUNT VESUVIUS. 257 the catastrophes by which it was attended ; but it had the good fortune to be accurately recorded by an eye- witness, Sir William Hamilton, who at that time repre- sented the English Government at the Court of Naples ; and we are thus more minutely acquainted with all its various circumstances than with those of any other eruption of equal importance. For two years before, the mountain had been- in a state of excitement and disturbance. From time to time rumbling noises were heard underground, dense masses of smoke were emitted from the crater, liquid lava at a white heat bubbled up from crevices on the slopes of the mountain, and through these crevices a glimpse could be had here and there of the rocky caverns within, all " red-hot like a heated oven." But in the month of August, 1779, the eruption reached its climax. About nine o'clock in the evening of Sunday the eighth, ac- cording to the graphic description of Sir William Ha- milton, " there was a loud report, which shook the houses at Portici and its neighbourhood to such a de- gree, as to alarm the inhabitants and drive them out into the streets. Many windows were broken, and, as I have since seen, walls cracked, from the concussion of the air from that explosion. In one instant, a fountain of liquid transparent fire began to rise, and, gradually in- creasing, arrived at so amazing a height, as to strike every one who beheld it with the most awful astonish- ment. I shall scarcely be credited when I assure you that, to the best of my judgment, the height of this stu- pendous column of fire could not be less than three S 258 DESCRIPTION BY AN EYE-WITNESS. times that of Vesuvius itself, which, you know, rises perpendicularly near 3,700 feet above the level of the sea. Puffs of smoke, as black as can possibly be ima- gined, succeeded one another hastily, and accompanied the red-hot, transparent, and liquid lava, interrupting its splendid brightness here and there by patches of the darkest hue. Within these puffs of smoke, at the very moment of their emission from the crater, I could per- ceive a bright but pale electrical light playing about in zigzag lines. The liquid lava, mixed with scoriae and stones, after having mounted, I verily believe, at least 10,000 feet, falling perpendicularly onVesuvius, covered its whole cone, part of that of Somma, and the valley between them. The falling matter being nearly as vivid and inflamed as that which was continually issuing fresh from the crater, formed with it a complete body of fire, which could not be less than two miles and a half in breadth, and of the extraordinary height above men- tioned, casting a heat to the distance of at least six miles around it. The brushwood of the mountain of Somma was soon in a flame, which, being of a different tint from the deep red of the matter thrown out from the volcano, and from the silvery blue of the electrical fire, still added to the contrast of this most extraordinary scene. After the column of fire had continued in full force for nearly half an hour the eruption ceased at once, and Vesuvius remained sullen and silent."' 1 See Sir John Hereohel, Familiar Lectures on Scientific Subjects, pp. 16, 27. VOLCANIC CHAIN OF THE ANDES. 259 The existence, then, of intense heat within the Crust of the Earth may be regarded as an established fact wherever an active Volcano appears at the surface. Now let us consider for a moment the very extensive scale on which these fiery engines of Nature are distri- buted over the face of the Globe. First, on the great continent of America. The whole chain of the Andes — that stupendous ridge of mountains which stretches along the western coast of South America, from Tierra del Fuego on the south to the isthmus of Panama on the north, — is studded over with Volcanos, most of which have been seen in active eruption within the last 300 years. Passing the narrow isthmus of Panama, this line of Volcanos may still be traced through Guatemala to Mexico, and thence northwards even as far as the mouth of the Columbia Eiver. Here is a vast volcanic region extending fully 6,000 miles in length, and. spreading out its fiery arms, we know not how far, to the right and to the left. At Quito, just on the Equator, a branch shoots off towards the north-east, and, passing through New Granada and Venezuela, stretches away across the West India Islands, taking in St. Vincent, Dominica, Guada- loupe, and many others : while, in the opposite direc- tion, it is certain that the volcanic action extends west- ward, far away beneath the waters of the Pacific, though we have no definite means of ascertaining where its in- fluence ceases to be felt. Another vast train of active Volcanos is that which skirts the eastern and southern coasts of Asia. Com- mencing on the shores of Northwestern America, it s 2 26o VOLCANIC CHAINS OF EUROPE AND ASIA'. passes through, the Aleutian islands to Kamtschatka ; then, in a sort of undulating curve, it winds its course by the Kurile islands, the Japanese group, the Philip- pines, and the northeastern extremity of the Celebes, to the Moluccas. At this point it divides into two branches ; one going in a southeasterly direction to New Guinea, the Solomon islands, the Friendly islands, and New Zea- land ; the other pursuin^g a northwesterly course through Java and Sumatra into the Bay of Bengal. There is a third great line of volcanic fires which has been pretty well traced out by modern travellers, ex- tending through China and Tartary to the Caucasus ; thence over the countries bordering the Black Sea to the Grecian Archipelago ; then on to Naples, Sicily, the Lipari islands, the southern part of Spain andPortugal, and the Azores. Besides these there are numerous groups of Volcanos not apparently linked on to any regular Vol- canic chain, nor reduced as yet by scientific men to any general system ; — Mount Hecla, for instance, in Iceland, the Mountains of the Moon in central Africa, Owhyhee in the Sandwich islands, and many others rising up irre- gularly from the broad waters of the Pacific. From this brief outline some idea may be formed of the magnificent scale on which volcanic agency is deve- loped within the Crust of the Earth. It must be remem- bered, however, that any estimate based upon the enumeration we have given, would be, in all probability, far below the truth ; for we have mentioned those Vol- canos only which have attracted the notice of scientific men, or which have chanced to fall under the observa- EXTINCT VOLCANOS. 26 1 tion of travellers. Many others, doubtless, must exist in regions not yet explored, and in the profound depths of the seas and oceans, which cover nearly two-thirds of the area of our planet. Moreover, we have said nothing at all of extinct Volcanos — such as those of Auvergne in France, and of the Rocky Mountains in America — which have not been in active operation within historical times ; but in which, nevertheless, the hardened streams of lava, the volcanic ashes, and the cone-shaped mountains terminating in hollow craters, tell the story of eruptions in bygone ages, not less clearly than the blackened walls and charred timbers of some stately building bear witness to the passing wayfarer of a long extinguished conflagration. We contend, therefore, that the doctrine of intense sub- terranean heat is not a wild conjecture, but is based on a solid ground V70rk of facts. First, there is presumptive evidence. In every deep mine, in every deep sinking of whatever kind, the heat of the earth increases rapidly as we descend. Hot water comes from great depths, and never cold. Sometimes it is boiling : sometimes it has been converted into steam. All this is found to be the case universally, whenever an opportunity has oc- curred for making the trial ; and it seems to afford a strong presumption that if one could go still deeper, the heat would be found yet more intense, and would at length be capable of reducing to a liquid state the solid materials of which the earth is composed. Next, there is the direct testimony of our senses. A channel is opened from the depths below, flames are seen, red-hot 262 SUMMARY OF THE EVIDENCE. cindera are cast up, and molten rock is poured out over the surface of the Earth in a liquid stream of fire. This evidence, however, though direct and conclusive as far as it goes, is not universal. It proves that an intense vrhite heat prevails within the Crust of the Earth, not everywhere, but at least in those numerous and extensive regions where active Volcanos exist. So stands the case, as it seems to us, for the doctrine of subterranean heat as far as regards the fact of its existence. CHAPTER XV. SUBTERRANEAN HEAT — ITS POWERS ILLUSTRATED BY VOLCANOS. EFFECTS OP STJBTEERANEAN HEAT IN THE PEESENT AGE OP THE WORLD — VAST ACOOMDLATIONS OP SOLID MATTER PKOM THE ERUP- TIONS OP TOLCANOS — BURIED CITIES OF POMPEII AND HEROULA- NEUM — CURIOUS RELICS OP ROMAN LIFE — MONTE NUOVO — ERUPTION OF JORULLO IN THE PROVINCE OP MEXICO — SUMBAWA IN THE INDIAN AROHIPELAQO — VOLCANOS OF ICELAND — MOUNTAIN MASS OP ETNA THE PRODUCT OF VOLCANIC ERUPTIONS — ^VOLCANIC ISLANDS — IN THE ATLANTIC IN THE MEDITERRANEAN — SANTORIN IN THE GRECIAN ARCHIPELAGO. Having now sufficiently demonstrated the existence of intense subterranean heat, di£Eused, if not universally, at least very generally, beneath the superficial shell of the Earth, we shall next proceed to inquire if it is capable of effecting those physical changes which are ascribed to it in Geology ; — of producing land where none before existed, of upheaving the solid Crust of the Earth, of driving the ocean from its bed, of dislocating and con- torting solid masses of rock. The argument ,is still an appeal to facts. Such effects as these have been pro- duced by the agency of internal heat, under actual ob- servation, in the present age of the world ; and it is not unreasonable to attribute to the same cause similar phe- nomena in ages gone by. We will not run the risk of dissipating the force of this reasoning by attempting to expand it. It will be 264 HEECULANEUM AND POMPEII. enough for us to state the facts : we shall leave it to our readers to estimate for themselves the value of the argument. There are three forms, more or less distinct, though closely associated, under which the subterranean fires have exerted their power in modern times to disturb and modify the Physical Geography of the Globe ; — (i) the Volcano, (2) the Earthquake, and (3) the gentle Undulation of the Earth's Crust. Of these we shall speak in order. In the case of Volcanos, as we have already sufficiently conveyed, the hidden furnaces of the Earth find a vent for their surplus energies ; and when this vent is once established, that is to say, when the active Volcano has begun to exist, it seems probable that there is little fur- ther upheaval, properly so called, of the surface. Never- theless, Volcanos contribute largely to the formation of land by the vast accumulation of ashes, mud, and lava which they vomit forth. The destruction of Hercula- neum and Pompeii is a case in point. For eight days successively, in the year 79, the ashes and pumice stone cast up from the crater of Vesuvius, fell down in one unceasing shower upon these devoted cities ; while at the same time floods of water, carrying along the fine dust and light cinders, swept down the sides of the mountain in resistless torrents of mud, entering the houses, penetrating into every nook and crevice, and filling even the very wine jars in the underground cellars. At the present moment the layers of volcanic matter beneath which Pompeii has been slumbering for centu- HERCULANEUM AND POMPEII. 265 ries, are from twelve to fourteen feet over the tops of the houses. Loftier still is the pile that overlies the buried Herculaneum. This city, situated nearer to the base of the Volcano, has been exposed to the effects of many suc- cessive eruptions : and accordingly, spread out over the mass of ashes and pumice by which it was first over- whelmed, in the time of Pliny, we nowfind alternate layers of lava, and volcanic mud, together with fresh accumu- lations of ashes, to a height in many places of 11 2 feet, and nowhere less than 70. Nor was this ejected matter confined to these two populous towns. It was scattered far and wide over the country around, and has contri- buted in no small degree to that extraordinary richness and fertility for which the soil of Naples is so justly famed. As regards the production of land where none be- fore existed, here is one fact of singular significance. At the time of the eruption, in 79, Pompeii was a sea- port town to which merchantmen were wont to resort, and a flight of steps, which still remains, led down to the water's edge : it is now more than a mile distant from the coast, and the tract of land which intervenes is com- posed entirely of volcanic tuff and ashes. Gladly would we linger over the reminiscences of these luxurious and ill-fated cities. By the removal of the ashes, Pompeii is now laid open to view for at least one- third of its extent ; and a strange sight it is, this ancient Roman city thus risen as it were from the grave, — risen but yet lifeless, — with its silent streets, and its tenant- less houses, and its empty Forum. Wherever we turn 266 CURIOUS RELICS OF ROMAN LIFE. we have before us a curious and interesting picture, ghastly though it is, of the social, political, and domestic life of those ancient times, of the glory and the shame that hung around the last days of Pagan Rome ; — in the theatres and the temples, in the shops and the private houses, in the graceful frescos, in the elaborate mosaics, and, not least, in the idle scribblings on the walls, which, with a sort of whimsical reverence, have been spared by the destroying hand of Time. Then again what a host of singular relics are there to be wondered at : — ar- ticles of domestic use and luxury, kitchen utensils and surgical instruments ; female skeletons with the orna- ments and vanities of the world, rings and bracelets and necklaces, still clinging to their charred remains ; and, strangest perhaps of all, eighty-four loaves of bread, which were put into the oven to bake 1800 years ago, and were taken out only yesterday, with the baker's brand upon them, and the stamp of the baker's elbow still freshly preserved in the centre of each. No sub- ject could be more tempting to a writer, none more at- tractive to a reader. But our present purpose is to show the effects of Volcanos in elevating the level of the land j and so we must turn our back on the buried cities, and crossing the Bay of Naples, seek for a new illustration in the formation of Monte Nuovo, a lofty hill over- looking the ancient town of Pozzuoli. About one o'clock at night, on Sunday the twenty- ninth of September, 1538, flames were seen to issue from the ground close to the waters of the beautiful bay of Baiae. After a little, a sound like thunder was A NEW MOUNTAIN SUDDENLY THROWN UP. 267 heard, the eaxth waa rent asunder, and through the rent large stones, red-hot cinders, volcanic mud, and volumes of water, were furiously vomited forth, which covered the whole country around, reaching even as far as Naples and disfiguring its palaces and public buildings. The next morning it was found that a new mountain had been formed by the accumulation of ejected matter around the central opening. This mountain remains to the present day and is called the Monte Nuovo. In form it is a regular volcanic cone, four hundred and forty feet high, and a mile and a-half in circumference at its base, with an open crater in the centre, which descends nearly to the level of the sea. An eye-witness who has left us a minute account of this eruption, relates that on the third day he went up with many people to the top of the new hill, and looking down into the crater, saw the stones that had fallen to the bottom, " boiling up just as a caldron of water boils on the fire." The same writer informs us — and it is very much to our present purpose to note the fact — that immediately before the eruption began, the relative position of land and sea was mate- rially changed, the coast was sensibly upraised, the waters retired about two hundred paces, and multitudes of fish were raised high and dry upon the sand, a prey to the inhabitants of Pozzuoli.' ' See the elaborate work of Sir 'William Hamilton, entitled Campi Phlegraei, in whicli he gives a full account of the formation of Monte Nuovo, accompanied with coloured plates. He has preserved two in- teresting narratives of the eruption written at the timehy eye-witnesses. See also Lycll, Principles of Geology, vol. i., pp. 606-616. 268 VOLCANIC ERUPTION IN MEXICO. The Monte Nuovo is but a type of its class. If we travel westward 8000 miles from Naples to the more stu- pendous Volcanos of the New World, we may witness the same phenomena on a still grander scale. In the province of Mexico there is an elevated and extensive plain called Malpais, where for many generations the cotton plant, the indigo, and the sugar-cane, flourished luxuriantly in a soil richly endowed with natural gifts, and carefully cultivated by its industrious inhabitants. Everything was going on as usual in this smiling and prosperous region, and no one dreamed of danger, when suddenly in the month of June, 1759, subterranean sounds were heard attended with slight convulsions of the earth. These symptoms of internal commotion continued until the month of September, when they gradually died away, and tranquillity seemed to be 'restored. But it was only the delusive lull that precedes the fury of the storm. On the night • of the twenty-eighth of Sep- tember the rumbling sounds were heard again more violent than before. The inhabitants fled in consterna- tion to a neighbouring mountain, from the summit of which they looked back with wonder and dismay upon the utter annihilation of their homesteads and their farms. Flames broke out over an area half a square league in extent, the earth was burst open in many places, frag- ments of burning rock were thrown to prodigious heights in the air, torrents of boiling mud flowed over the plain, and thousands of little conical hills, called by the natives Hornitos or Ovens, rose up from the surface of the land. Finally, a vast chasm was opened, and FORMATION OF SIX GREAT MOUNTAIN MASSES. 269 such quantities of ashes and fragmentary lava were ejected as to raise up six great mountain masses, which continued to increase during the five months that the eruption lasted. The least of these is 300 feet high, and the central one, now called Jorullo, which is still burn- ing, is 1600 feet above the level of the plain. When Baron Humboldt visited this region just forty years after the eruption had ceased, the ground was still in- tensely hot, and " the Hornitos were pouring forth columns of steam twenty or thirty feet high, with a rum- bling noise like that of a steam boiler."' Since that time, however, the face of the country has become once more smiling and prosperous ; the slopes of the newly formed hills are now clothed with vegetation, and the sugar- cane and the indigo again flourish luxuriantly in the fertile plains below. On the opposite side of the Globe, 10,000 miles from Mexico, we have had, almost in our own time, an exhi- bition of volcanic phenomena not less wonderful than those we have been describing. The island of Sumbawa lies about two hundred miles to the east of Java in the Indian Archipelago ; and it belongs to that remarkable chain of Volcanos which we have already described as stretching, with little interruption, along the coast of Asia from Russian America to the Bay of Bengal. In the year 1 8 1 5 this island was the scene of a calamitous eruption, the effects of which were felt over the whole ' Sir Jolin Herschel, Familiar Lectures on Scientific Subjects, p. 34 ; see also Lyell, Principles of Geology, chap, xxvii. ; Mantell, Wonders of Geology, pp. 872-4. 270 ERUPTION IN THE ISLAND OF SUMBAWA. of the Molucca Islands and Java, as well as over a con- siderable portion of Celebes, Sumatra, and Borneo. In- deed so extraordinary are the incidents of this eruption, that we might well hesitate to believe them, if they had not been collected on the spot with more than ordinary diligence, and recorded with an almost scrupulous care. Sir Stamford Raffles, who was at the time governor of Java, then a British possession, required all the resi- dents in the various districts under his authority to send in a statement of the circumstances which occurred within their own knowledge ; and from the accounts he received in this way, combined with other evidence, chiefly obtained from eye-witnesses, he drew up the narrative to which we are mainly indebted for the fol- lowing facta. The explosions which accompanied this eruption were heard in Sumatra, at a distance of 970 geographical miles ; and in the opposite direction at Ternate, a distance of 720 miles. In the neighbourhood of the Volcano itself, immen'Se tracts of land were covered with burning lava, towns and villages were overwhelmed, all kinds of vege- tation completely destroyed, and of 1 2,000 inhabitants in the province of Tomboro, only twenty-six survived. The ashes, which were ejected in great quantities, were carried like a vast cloud through the air, by the south- east monsoon, for 300 miles in the direction of Java; and, still farther to the west, we are told they formed a floating mass in the ocean, two feet thick and several miles in extent, through which ships with difficulty forced their way. It is recorded, too, that they fell so thick on SUDDEN SUBSIDENCE OF THE LAND. 27 1 the island of Tombock, loo miles away, as to cover all the land two feet deep, destroying every particle of ve- getation, insomuch that 44,000 people perished of the famine that ensued. " I have seen it computed," writes Sir John Herschel, " that the quantity of ashes and lava vomited forth in this awful eruption would have formed three mountains the size of Mont Blanc, the highest of the Alps ; and if spread over the surface of Germany, would have covered the whole of it two feet deep." Finally, it appears that this eruption was accompanied, like that of Monte Nuovo, by a permanent change in the level of the adjoining coast ; in this case, however, it was a movement, not of upheaval, but of subsidence : the town of Tomboro sunk beneath the ocean, which is now eighten feet deep where there was dry land be- fore.* Once more we will ask our readers to take a rapid flight over the map of the world, passing this time from the Indian Archipelago to the island of Iceland, — that " wonderful land of frost and fire." Besides the famous Volcano of Heola, there are five others scarcely less formidable, all of which have been in active eruption within modern times. Of these the most celebrated is that of Skapljar Jokul. In the year 1783 this Volcano poured forth two streams of lava, which, when hardened, formed together one continuous layer of igneous rock, ninety miles in length, a hundred feet in height, and ' See Hersohel, Familiai Lectures on Scientific Subjects, pp. 34-6 ; Lyell, Principles of Geology, vol. ii., pp. 104-6. 272 VOLCANOS OF ICELAND. from seven to fifteen miles in breadth. The phenomena which accompanied the eruption are thus vividly de- scribed by Sir John Herschel : — " On the tenth of May innumerable fountains of fire were seen shooting up through the ice and snow which covered the mountain ; and the principal river, called the Skapta, after rolling down a flood of foul and poisonous water, disappeared. Two days after, a torrent of lava poured down into the bed which the river had deserted. The river had run in a ravine, 600 feet deep and 200 broad. This the lava entirely filled ; and not only so, but it overflowed the surrounding country, and ran into a great lake, from which it instantly expelled the water in an explosion of steam. When the lake was fairly filled, the lava again overflowed and divided into two streams, one of which covered some ancient lava fields ; the other re-entered the bed