The Story of the Earth and Man

Front matter

NATURE, SCIENCE, AND REVELATION. In large crown Svo, price 9s., cloth. THE HIGHER MINISTRY OE NATURE VIEWED IN THE LIGHT OF MODERN SCIENCE. BY JOHN H. LEIFCHIliD, A.M., AUTHOR OF "OCR COAL FIELDS AND OUR COAL PITS;" "CORNWALL: ITS MINES AND MINERS," ETC, ETC. " Mr. Leifchild is well known from his contributions to the practical departments of Physical Geography. He writes with great vigour and charm of style, and has acquired by long communion with Nature the right to speak of its higher ministry, and of the ' authentic tidings ' which it brings from the mind and heart and will of God."— British Quarterly Review. " This is an able and interesting book, and one which for its purpose and scope we are glad to have an opportunity of recommending." — Globe. " Mr. Leifchild does not fear to confront the most advanced theories of mere Naturalism in a free and fair spirit.

His book is one of sound knowledge and sober thought, and is likely to be useful at the present time." — Illustrated London News. " The author takes up his position under circumstances that entitle him to a fair and impartial hearing on either side. He is known to science as a writer on geological subjects, whose contributions deserve the highest respect, while his right to be heard as a theologian is manifest in the conservative yet purely scientific spirit in which theology is treated. A timely and in many senses a rich contribution to the mental ne cessities of our times ; it is the work of a mind comprehensive inits grasp, deep in its sympathy with nature, and strong in its love of truth. Its scope is broad, comprising on the one hand the largest questions possible to thought, and on the other the minutest details of the latest research.

The philosophy of death, the question of resurrection, the certainty of immortality, the future continuity of our knowledge of God in His works, and the consequent heaven of mind, are all considered with the reverence of a Christian and the calmness of a man of science. The author seizes with exquisite aptitude the latest discourses and hypotheses of science, and by analogical reasoning marshals them in support and elucidation of the highest claims of religious thought." — London Quarterly Review. THE STORY Of THE EARTH AND MAN DIAGRAM or THE EARTHS HISTORY. THE STORY OF THE EARTH AND MAN. 1:Y J. W. DAWSON, LL.D., F.R.S., F.G.S., PRINCIPAL AND VICE-CHANCELLOR OF McGILL UNIVERSITY. MONTREAL , AUTHOR OF "ARCHAIA," "ACADIAN GEOLOGY," ETC. iLonbon: HODDER AND STOUGHTON, 2.7, PATERNOSTER ROW. JVIDCCCLXXIII. Butler & Tanner, The Selwood Printing Works, Frome, and London.

Preface

. The science of the earth as illustrated by geological research, is one of the noblest outgrowths of our modern intellectual life. Constituting the sum of all the natural sciences in their application to the history of our world, it affords a very wide and varied scope for mental activity, and deals with some of the grandest problems of space and time and of organic existence. It invites us to be present at the origin of things, and to enter into the very workshop of the Creator. It has, besides, most important and intimate connection with the industrial arts and with the material resources at the disposal of man. Its educational value, as a means of cultivating the powers of ob serving and reasoning, and of accustoming the mind to deal with large and intricate questions, can scarcely be overrated.

But fully to serve these high ends, the study of geology must be based on a thorough knowledge of the subjects which constitute its elementary data. It must be divested as far as possible of merely local colouring, and of the prejudices of specialists. It must be emancipated from the control of the bald metaphysical speculations so rife in our time, and

PREFACE.

. VIII above all it must be delivered from that materialistic infidelity, which, by robbing nature of the spiritual element, and of its presiding. Divinity, makes science dry, barren, and repulsive, diminishes its educational value, and even renders it less efficient for purposes of practical research. That the want of these preliminary conditions mars much of the popular science of our day is too evident ; and I confess that the wish to attempt something better, and thereby to revive the interest in geological study, to attract attention to its educational value, and to remove the misapprehensions which exist in some quarters respecting it, were principal reasons which induced me to undertake the series of papers for the Leisure Hour, which are reproduced, with some amend ments and extension, in the present work.

How far I have succeeded, I must leave to the intelligent and, I trust, indulgent reader to decide. In any case I have presented this many-sided subject in the" aspect in which it appears to a geologist whose studies have led him to compare with each other the two great continental areas which are the classic ground of the science, and who retains his faith in those unseen realities of which the history of the earth itself is but one of the shadows projected on the field of time. To geologists who may glance at the following

PREFACE.

. IX pages, I would say that, amidst much that is familiar, they will find here and there some facts which may be new to them, as well as some original suggestions and conclusions as to the relations of things, which though stated in familiar terms, I have not advanced without due consideration of a wide range of facts. To the general reader I have endeavoured to present the more important results of geological investigation divested of technical difficulties, yet with a careful re gard to accuracy of statement, and in such a manner as to invite to the farther and more precise study of the subject in nature, and in works which enter into technical details. I have endeavoured as far as pos sible to mention the authors of important discoveries ; but it is impossible in a work of this kind to quote authority for every statement, while the omission of much important matter relating to the topics discussed is also unavoidable.

Shortcomings in these respects must be remedied by the reader himself, with the aid of systematic text-books. Those who may desire any farther explanation of the occasional allusions to the record of creation in Genesis, will find this in my previously published volume entitled " Archaia." J. W. D. McGill College, Montreal, January, 1873. PAGK 1 CONTENTS. Chapter I. — The Genesis or the Earth. Uniformity and Progress. — Internal Heat. — Nebular Theory. — Probable Condition of the Primitive World Chapter II. — The Bozoic Ages. The Laurentian Rocks. — Their Character and Distribution. — The Conditions of their Deposition. — Their Metamorphism. — Eozoon Canadense. — Laurentian Vegetation 17 Chapter III. — The Primordial or Cambrian Age. Connection of the Laurentian and Primordial. — Animals of the Primordial Seas. — Lingula, Trilobites, Oldhamia, etc. — The terms Cambrian and Silurian. — Statistics of Primordial Life ..... 36 Chapter TV. — The Silurian Ages.

Geography of the Continental Plateaus. — Life of the Silurian. — Reign of Invertebrates. — Corals, Crinoids, Mollusks, Crustaceans. — The First Vertebrates. — Silurian Fishes.— Land Plants 56 Chapter V. — The Devonian or Erian Age. Physical Character of the Age. — Difference of Deposits in Marginal and Continental Areas. — Specialisation of Physical Geography.— Corals, Crustaceans, Fishes, Insects, Plants CONTENTS. XII Chapter VI. — The Carboniferous Age. page Perfection of Palæozoic Life. — Carboniferous Geography. — Colours of Sediments. — Vegetation. — Origin of Coal. — Land Life. — Reptiles, Land Snails, Millipedes, etc. — Oceanic Life 109 Chapter VII. — The Permian Age. Movements of the Land. — Plication of the Crust. — Chemical Conditions of Dolomite, etc. — Geographical Results of Permian Movements. — Life of the Period. — Summary of Palæozoic History .... 160 Chapter VIII. — The Mesozoic Ages.

Characters of the Trias. — Summary of Changes in the Triassic and Cretaceous Periods. — Changes of the Continental Plateaus. — Relative Duration of the Palæozoic and Mesozoic. — -Mesozoic Forests. — Land Animals. — The reign of Reptiles. — Early Mammals and Birds 188 Chapter IX. — The Mesozoic Ages — (continued). Animals of the Sea. — Great Sea Lizards, Fishes, Cephalopods, etc. — -Chalk and its History. — Tabular View of the Mesozoic Ages 211 Chapter X. — The Neozoic Ages. Physical Changes at the end of Mesozoic. — Subdivisions of the Neozoic. — Great Eocene Seas. — Land Animals and Plants. — Life of the Miocene. — Reign of Mammals 235 Chapter XI. — The Neozoic Ages — (continued). Later Vegetation. — The Animals of the Pliocene Period. — Approach of the Glacial Period. — Character of the Post-pliocene or Glacial CONTENTS.

XIII PAGE 299 Chapter XII. — Close of the Post-Pliocene, and Advent op Man. Connection of Geological and Human History. — The Post-glacial Period. — Its Relations to the Pre-Historic Human Period. — Elevation of Post-Pliocene Land. — Introduction of Man. — Subsidence and Re-elevation. — Calculations as to Time. — Tabular View of the Neozoic Ages 282 Chapter XIII. — Advent op Man — (continued). Relations of Post-pliocene and Modern Animals. — Cavern Deposits. — Kent's Cave. — General Remarks Chapter XIV. — Primitive Man. Theory of Evolution as applied to Man. — Its Demands. — Its Deficiencies. — Fallacious Character of Arguments of Derivationists. — Hypothesis of Creation. — Its Demands and Advantages 316 Chapter XV. — Primitive Man — (continued). Geological Conditions of Man's Introduction. — His Modern Date. — His Isolated Position. — His Higher Powers. — Pictures of Primitive Man according to Evolution and Creation. — General Conclusions LIST OF ILLUSTRATIONS.

PAGE Ideal Sections Illustrating the Genesis of the Earth 8 America in the Laurentian Period 18 Eozoon Canadense 24 Life in the Primordial Age 40 Organic Limestone of the Silurian . . . .63 Life in the Silurian 6S Life in the Devonian 88 Vegetation of the Devonian 103 Carboniferous Plants 126 Oldest Land Snails 139 Carboniferous Reptiles 146 Foldings of the Crust in the Permian Period . .162 Curves of Elevation and Depression . . . . 179 Culmination of Types of Palæozoic Animals . . . 183 Land Animals of the Mesozoic 194 Aquatic Animals of the Mesozoic . . . . 219 FoRAMINIFERAL ROCK-BUILDERS 243 Miocene Mammals . . . . . . . . 253 Britain in the Post-pliocene %\t Storg 0s % €ixxt\ antr Pair.

Chapter I. The Genesis Of The Earth

The title of this work is intended to indicate precisely its nature. It consists of rough, broad sketches of the aspects of successive stages in the earth's history, as disclosed by geology, and as they present themselves to observers at the present time. The last qualification is absolutely necessary, when dealing with a science whose goal to-day will be its starting point to-morrow, and in whose view every geological picture must have its light and shaded portions, its clear foreground and its dim distance, varying according to the lights cast on them by the progress of investigation, and accord ing to the standpoint of the observer. In such pic tures results only can be given, not the processes by which they have been obtained ; and with all possible gradations of light and distance, it may be that the artist will bring into too distinct outline facts still only dimly perceived, or will give too little prominence to B THE STOEY OF THE EARTH AND MAN. others which should appear in bold relief.

He must in this judge for himself; and if the writer's impressions do not precisely correspond with those of others, he trusts that they will allow something for difference of vision and point of view. The difficulty above referred to perhaps rises to its maximum in the present chapter. For how can any one paint chaos, or give form and filling to the form less void ? Perhaps no word-picture of this period of the first phase of mundane history can ever equal the two negative touches of the inspired penman — "without form and void" — a world destitute of all its present order, and destitute of all that gives it life and animation. This it was, and not a complete and finished earth, that sprang at first from its Creator's hand ; and we must inquire in this first chapter what information science gives as to any such condition of the earth.

In the first place, the geological history of the earth plainly intimates a beginning, by utterly negativing the idea that "all things continue as they were from the creation of the world." It traces back to their origin not only the animals and plants which at present live, but also their predecessors, through successive dynasties emerging in long procession from the depths of a primitive antiquity. Not only so; it assigns to their relative ages all the rocks of the earth's crust, and all the plains and mountains built up of them. Thus, as we go back in geological time, we leave behind us, one by one, all the things with which we are familiar, and the inevitable conclusion gains on us that we must be approaching a beginning, though this may be veiled from us in clouds and thick darkness. How is it, then, that there are " Uniformitarians" in geology, and that it has been said that our science shows no traces of a beginning, no indications of an end ?

The question deserves consideration ; but the answer is not difficult. In all the lapse of geological time there has been an absolute uniformity of natural law. The same grand machinery of force and matter has been in use throughout all the ages, working out the great plan. Yet the plan has been progressive and advancing, nevertheless. The uniformity has been in the methods, the results have presented a wondrous diversity and development. Again, geology, in its oldest periods, fails to reach the beginning of things. It shows us how course after course of the building has been laid, and how it has grown to completeness, but it contains as yet no record of the laying of the foundation-stones, still less of the quarry whence they were dug. Still the constant progress which we have seen points to a beginning which we have not seen; and the very uniformity of the process by which the edifice has been erected, implies a time when it had not been begun, and when its stones were still repos ing in their native quarry.

What, then, is the oldest condition of the earth actually shown to us by geology, — that which prevailed in the Eozoic or Laurentian period, when the oldest rocks known, those constituting the foundationstones of our present continents, were formed and laid in their places ? With regard to physical conditions, it was a time when our existing continents were yet in the bosom of the waters, when the ocean was almost universal, yet when sediments were being deposited in it as at present, while there were also volcanic foci, vomiting forth molten matter from the earth's hidden interior. Then, as now, the great physical agencies of water and fire were contending with one another for the mastery, doing and undoing, building up and breaking down. But is this all? Has the earth no earlier history ?

That it must have had, we may infer from many indications ; but as to the nature of these earlier states, we can learn from conjecture and in ference merely, and must have recourse to other witnesses than those rocky monuments which are the aure guides of the geologist. One fact bearing on these questions which has long excited attention, is the observed increase in tempera ture in descending into deep mines, and in the water of deep artesian wells — an increase which may be stated in round numbers at one degree of heat of the centigrade thermometer for every 100 feet of depth from the surface. These observations apply of course ro a very inconsiderable depth, and we have no certainty that this rate continues for any great distance towards the centre of the earth. If, however, we regard it as indicating the actual law of increase of temperature, it would result that the whole crust of the earth is a mere shell covering a molten mass of rocky matter.

Thus a very slight step of imagination would carry us back to a time when this slender crust had not yet formed, and the earth rolled through space an incandescent globe, with all its water and other vaporisable matters in a gaseous state. As tronomical calculation has, however, shown that the earth, in its relation to the other heavenly bodies, obeys the laws of a rigid ball, and not of a fluid globe. Hence it has been, inferred that its actual crust must be very thick, perhaps not less than 2,500 miles, and that its fluid portion must therefore be of smaller dimensions than has been inferred from the observed increase of temperature. Further, it seems to have been rendered probable, from the density of rocky matter in the solid and liquid states, that a molten globe would solidify at the centre as well as at the surface, and consequently that the earth must not only have a solid crust of great thickness, but also a solid nucleus, and that any liquid portions must be of the nature of a sheet or of detached masses intervening between these.

On the other hand, it has recently been maintained that the calcu lations which are supposed to have established the great thickness of the crust, on the ground that the earth does not change its form in obedience to the attraction of the sun and moon, are based on a mis conception, and that a molten globe with a thin crust would attain to such a state of equilibrium in this respect as not to be distinguishable from a solid planet. This view has been maintained by the French physicist, Delaunay, and for some time it made geologists suppose that, after all, the earth's crust may be very thin. Sir William Thomson, however, and Archdeacon Pratt, have ably maintained the previous opinion, based on Hopkins' calculations ; and it is now believed that we may rest upon this as representing the most probable condition of the interior of the earth at present.

Another fact bearing on this point is the form of the earth, which is now actually a spheroid of rotation; that is, of such a shape as would result from the action of gravity and centrifugal force in the motion of a huge liquid drop rotating in the manner in which the earth rotates. Of course it may be said that the earth may have been made in that shape to fit it for its rotation ; but science prefers to suppose that the form is the result of the forces acting on it. This consideration would of course corroborate the deductions from that just mentioned. Again, if we examine a map showing the distribution of volcanoes upon the earth, and trace these along the volcanic belt of Western America and Eastern Asia, and in the Pacific Islands, and in the isolated volcanic regions in other parts of the world ; and if we add to these the multitude of volcanoes now extinct, we shall be convinced that the sources of internal heat, of which these are the vents, must be present almost everywhere under the earth's crust.

Lastly, if we consider the elevations and depressions which large portions of the crust of the earth have undergone in geological time, and the actual crumpling and folding of the crust visible in great mountain chains, we arrive at a similar conclusion, and also become convinced that the crust has been not too thick to admit of extensive fractures, flexures, and foldings. There are, however, it must be admitted, theories of volcanic action, strongly supported by the chemical nature of the materials ejected by modern volcanoes, which would refer all their phenomena to the softening, under the continued influence of heat and water, of materials within the crust of the earth rather than under it.* Still, the phenomena of vol canic action, and of elevation and subsidence, would, under any explanation, suppose intense heat, and therefore probably an original incandescent condition.

La Place long ago based a theory of the originally gaseous condition of the solar system on the relation of the planets to each other, and to the sun, on their planes of revolution, the direction of their revolution, and that of their satellites. On these grounds he inferred that the solar system had been formed out of a nebulous mass by the mutual attrac tion of its parts. This view was further strengthened by the discovery of nebulæ, which it might be supposed were undergoing the same processes by which the solar system was produced. This nebular theory, as it was called, was long very popular. It was subsequently supposed to be damaged by the fact that some of the nebulæ which had been regarded as systems in progress of formation were found by im- * Dr. T. Sterry Hunt, in Silliman's Journal, 1870. proved telescopes to be really clusters of stars, and it was inferred that the others might be of like character.

The spectroscope has, however, more recently shown that some nebulæ are actually gaseous ; and it has even been attempted to demonstrate that Figs. 1 to 5. Ideal sections illustrating the Genesis of the Earth. Fig. 1. A vaporous world. Fig. 2. A world with a central fluid nucleus (6) and a photosphere (a). Fig. 3. The photosphere darkened, and a solid crust (c) and solid nucleus (d) formed. Fig. 4. Water (e) deposited on the crust, forming a universal ocean. Fig. 5. Tbe crust crumpled by shrinkage, land elevated, and the water occupying the intervening depressions. The figures are all of uniform size ; but the circle (A) shows the diameter of the globe when in the state of fig. 1, and that marked (B) its diameter when in the state of fig. 5. In all the figures (a) represents vapour or air; (6) liquid rock; (c) solid rock as a crust; (d) solid nucleus ; (e) water. they are probably undergoing change fitting them to become systems.

This has served to revive the nebular hypothesis, which has been further strengthened by the known fact that the sun is still an incandescent globe surrounded by an immense luminous envelope of vapours rising from its nucleus and con densing at its surface. On the other hand, while the sun may be supposed, from its great magnitude, to remain intensely heated, and while it will not be appreciably less powerful for myriads of years, the moon seems to be a body which has had time to complete the whole history of geological change, and to become a dry, dead, and withered world, a type of what our earth would in process of time actually become. Such considerations lead to the conclusion that the former watery condition of our planet was not its first state, and that we must trace it back to a previous reign of fire.

The reasons which can be adduced in support of this are no doubt somewhat vague, and may in their details be variously interpreted ; but at present we have no other interpretation to give of that chaos, formless and void, that state in which " nor aught nor nought existed," which the sacred writings and the traditions and poetry of ancient nations concur with modern science in indicating as the primitive state of the earth. Let our first picture, then, be that of a vaporous mass, representing our now solid planet spread out over a space nearly two thousand times greater in diameter than that which it now occupies, and whirling in its annual round about the still vaporous centre of our system, in which at an earlier period the earth had been but an exterior layer, or ring of vapour. The atoms that now constitute the most solid rocks are in this state as tenuous as air, kept apart by the expansive force of heat, which prevents not only their mechanical union, but also their chemical combination.

But within the mass, slowly and silently, the force of gravitation is compressing the particles in its giant hand, and gathering the denser toward the centre, while heat is given forth on all sides from the condensing mass into the voids of space without. Little by httle the denser and less volatile matters collect in the centre as a fluid molten globe, the nucleus of the future planet ; and in this nucleus the elements, obeying their chemical affinities hitherto latent, are arranging themselves in compounds which are to constitute the future rocks. At the same time, in the exterior of the vaporous envelope, matters cooled by radiation into the space without, are combining with each other, and are being precipitated in earthy rain or snow into the seething mass within, where they are either again vaporised and sent to the surface or absorbed in the increasing nucleus.

As this process advances, a new brilliancy is given to the faint shining of the nebulous matter by the incandescence of these solid particles in the upper layers of its atmosphere, a condition which at this moment, on a greater scale, is that of the sun ; in the case of the earth, so much smaller in volume, and farther from the centre of the system, it came on earlier, and has long since passed away. This was the glorious starlike condition of our globe : in a physical point of view, its most perfect and beautiful state, when, if there were astronomers with telescopes in the stars, they might have seen our now dull earth flash forth — a brilliant white star secondary to the sun. But in process of time this passes away. All the more solid and less volatile substances are condensed and precipitated ; and now the atmosphere, still vast iu bulk, and dark and misty in texture, contains only the water, chlorine, carbonic acid, sulphuric acid, and other more volatile substances ; and as these gather in dense clouds at the outer surface, and pour in fierce corrosive rains upon the heated nucleus, combining with its materials, or flashing again into vapour, darkness dense and gross settles upon the vaporous deep, and continues for long ages, until the atmosphere is finally cleared of its acid vapours and its superfluous waters.* In the meantime, radiation, and the heat abstracted from the liquid nucleus by the showers of condensing material from the atmosphere, have so far cooled its surface that a crust of slag or cinder forms upon it.

Broken again and again by the heav ings of the ocean of fire, it at length sets permanently, and receives upon its bare and blistered surface the ever-increasing aqueous and acid rain thrown down * Hunt, " Chemistry of the Primeval Earth," Silliman's Journal, 1858. from the atmosphere, at first sending it all hissing and steaming back, but at length allowing it to remain a universal boiling ocean. Then began the reign of the waters, and the dominion of fire was confined to the abysses within the solid crust. Under the prime val ocean were formed the first stratified rocks, from the substances precipitated from its waters, which must have been loaded with solid matter. We must not imagine this primeval ocean like our own blue sea, clear and transparent, but filled with earthy and saline matters, thick and turbid, until these were per mitted to settle to the bottom and form the first sediments.

The several changes above referred to are represented in diagrammatic form in figs. 1 to 4. In the meantime all is not at rest in the interior of the new-formed earth. Under the crust vast oceans of molten rock may still remain, but a solid interior nucleus is being crystallised in the centre, and the whole interior globe is gradually shrinking. At length this process advances so far that the exterior crust, like a sheet of ice from below which the waber has subsided, is left unsupported; and with terrible earthquake-throes it sinks downward, wrinkling up into huge folds, between which are vast sunken areas into which the waters subside, while from the inter vening ridges the earth's pent-up fires belch forth ashes and molten rocks. (Fig. 5.) So arose the first dry land : — " The mountains huge appear Emergent, and their broad bare backs upheave Into the clouds, their tops ascend the sky, So high as heaved the tumid hills, so low Down sunk a hollow bottom, broad and deep, Capacious bed of waters."

The cloud was its garment, it was swathed in thick darkness, and presented but a rugged pile of rocky precipices ; yet well might the " morning stars sing together, and all the sons of God shout with joy," when its foundations were settled and its corner stone laid, for then were inaugurated the changes which were to lead to the introduction of life on the earth, and to all the future development of the con tinents. Physical geographers have taught us that the great continents, whether we regard their coasts or their mountain chains, are built up on lines which run north-east and south-west, and north-west and south east ; and it is also observed that these lines are great circles of the earth tangent to the polar circle. Fur ther, we find, as a result of geological investigation, that these lines determined the deposition and the elevation of the oldest rocks known to us.

Hence it is fair to infer that these were the original directions of the first lines of fracture and upheaval. Whether these lines were originally drawn by the influence of of the seasons on the cooling globe, or by the cur rents of its molten interior, or of the superficial ocean, they bespeak a most uniform and equable texture for the crust, and a definite law of fracture and upheaval ; and they have modified all the subsequent action of the ocean as a depositor of sediment, and of the internal heat as a cause of alteration and movement of rocks. Against these earliest belts of land the ocean first chafed and foamed. Along their margins marine denudation first commenced, and the oceanic currents first deposited banks of sediment ; and along these first lines have the volcanic orifices of all periods been most plentiful, and elevatory movements most powerfully felt.