THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID SOME SALIENT POINTS IN THE SCIENCE OF THE EARTH BY SIR J. WILLIAM DAWSON C.M.G., LL.D., F.R.S., F.G.S., ETC. WITH FORTY-SIX ILLUSTRATIONS HODDER AND STOUGHTON 27, PATERNOSTER ROW MDcccxcni WORKS BY THE SAME AUTHOR. Modern Science in Bible Lands. With Illus- trations. Popular Edition, Revised. Crown 8vo, 6/- The Origin of the World, according to Revela- tion and Science. Sixth Edition. Crown 8vo, cloth, 7/6. The Story of the Earth and Man. Tenth Edition, with Twenty Illustrations. Crown 8vo, cloth, 7/6. Fossil Men and Their Modern Representa- tives. An attempt to illustrate the Characters and Con- dition of Pre-historic Men in Europe, by those of the American Races. With numerous Illustrations. Third Edition. Crown 8vo, cloth, 7/6. LONDON : HODDER AND STOUGHTON. EARTH SCIENCES LIBRARY PREFACE. *T"^HE present work contains much that is new, and much in correction and amplification of that which is old ; and is intended as a closing deliverance on some of the more important questions of geology,, on the part of a veteran worker, conversant in his younger days with those giants of the last generation, who, in the heroic age of geological science, piled up the mountains on which it is now the privilege of their successors to stand. J. W. D. Montreal, 1893. s. F. CONTENTS. CHAPTER I. FACE THE STARTING-POINT . . . . . ' . . . . 3 CHAPTER II. WORLD-MAKING .... . . . . . . 9 CHAPTER III. THE IMPERFECTION OF THE GEOLOGICAL RECORD ... 39 CHAPTER IV. THE HISTORY OF THE NORTH ATLANTIC . . . . '. 57 CHAPTER V. THE DAWN OF LIFE . . : 95 CHAPTER VI. WHAT MAY BE LEARNED FROM EOZOON 135 CHAPTER VII. THE APPARITION AND SUCCESSION OF ANIMAL FORMS . . 169 CHAPTER VIII. THE GENESIS AND MIGRATIONS OF PLANTS . . . . 201 CHAPTER IX. THE GROWTH OF COAL . . . . . . . . 233 Vlll CONTENTS. CHAPTER X. fAGE THE OLDEST AIR-BREATHERS . . . . . . 257 CHAPTER XI. MARKINGS, FOOTPRINTS, AND FUCOIDS 311 CHAPTER XII. PRE-DETERMINATION IN NATURE 329 CHAPTER XIII. THE GREAT ICE AGE 345 CHAPTER XIV. CAUSES OF CLIMATAL CHANGE 383 CHAPTER XV. THE DISTRIBUTION OF ANIMALS AND PLANTS AS RELATED TO GEOGRAPHICAL AND GEOLOGICAL CHANGES . . .401 CHAPTER XVI. ALPINE AND ARCTIC PLANTS IN CONNECTION WITH GEOLOGICAL HISTORY 425 CHAPTER XVII. EARLY MAN 459 CHAPTER XVIII. MAN IN NATURE 481 ERRATA IN LIST AND LEGENDS OF ILLUSTRATIONS, ETC. Owing to an illness while the work was in press, the author was unable to revise proofs of the Legends of the Illustrations ; hence the following errata. List of Illustrations. Page ix, for "Tabulate" read " Tabulate." Page x, for " Palaeography " read " Palaeo^ography. " Cambro-silurian Sponges, page 39. For " Lanothrix " read " Lasiothrix." ,, " Palasosamis " read " Palaeosamis." Specimen of Eozoon, page 135. For " Genera " read " Genera/." Diagram of Coral, page 139. For " Tabulate" read "Tabulate." Primitive Fishes, page 185. For " Pterichthws " read " Pterichthys." Pupa and Conulus, page 289. For " Darwin" read " Dawson." " prisca " read " priscus." In note for figured " above " read figured "here." Carboniferous Millipedes, page 295. For " Darwin " read " Dawson." Footprints of Limulus, page 311. For " Protechnites " read " Protzchnites. " Restoration of Protospongia, page 329. For " Giluru-" read " Siluro-." Maps of North America, page 383. For " surmergence" read " submergence." Distribution of Animals, page 401. After "Cuttlefishes" insert " 6. Brachiopods. " Page 485, line 10 from bottom, for " physical" read " psychical.' LIST OF ILLUSTRATIONS. PAGE Cape Trinity on the Saguenay . . . . , . , Frontispiece Folding of the Earth's Crust . . . . . To face 9 Cambro-Silurian Sponges V . . . . . ,, 39 Map of the North Atlantic . . .. . . . ,, 57 Nature- print of Eozoon . . . . ... 95 Laurentian Hills, Lower St. Lawrence . . ... - .' ... 100 Section from Petite Nation Seigniory to St. Jerome . . . 101 The Laurentian Nucleus of the American Continent . . . 103 Attitude of Limestone at St. Pierre . ... . . 109 Weathered Eozoon and Canals ; . ' . ' . . . To face 112 . . . . . ."3 Group of Canals in Eozoon . . . . ... .11$ Amoeba and Actinophrys . . 119 Minute Foraminiferal Forms . . . . . . . .123 Section of a Nummulite . . 127 Portion of Shell of Calcarina .. . . . .... 128 \VeatheredEozoonwithOsculartubes . ... . To face 135 Diagram showing different States of Fossilization of a Cell of a Tubulate Coral . ..... . . . 1 39 Slice of Crystalline Lower Silurian Limestone . . . .141 Walls of Eozoon penetrated with Canals . . . . .141 Joint of a Crinoid 145 Shell from a Silurian Limestone, Wales .146 Casts of Canals of Eozoon in Serpentine . . . . .147 Canals of Eozoon r 147 Primordial Trilobites . ... To face 169 Primitive Fishes . . " v . . . ,, 185 Devonian Forest . . . . . . * . ,, 201 Coal Section in Nova Scotia ...... 233 ILLUSTRATIONS. PAGE Skeleton of Hylonomus Lyelli . . . .' . To face 257 Footprints of Hylopus Logani ,, 261 Humerus and Jaws of Dendrerpetou . . . . ,, 273 Reptiliferous Tree . ...... . . . . ,, 277 Microsaurian, restored . . . . . . - . ,, 279 Dolichosoma longissimiim^ restored . . . . ,, 287 Pupa and Conulus . . . . . - . . . , , 289 Millipedes and Insect . . . ... . ,, 295 Footprints of Limulus . . " . ' . . . . ,, 311 Rusichnites Grenvillensis . . . ,, 323 Restoration of Protospongia tetranema . '-. ... ,, 329 Giant Net-sponge . . . . " . ' * . . . ' ,, 337 Boulder Beach, Little Metis . .."..-, ,, 345 Palaeography of North America . . . ... ,, 383 Distribution of Animals in Time ..... ,, 401 Tuckerman's Ravine and Mount Washington > . ,, 425 Pre-historic Skulls , . ,, 459 Primitive Sculpture ,, 481 TABLE OF GEOLOGICAL HISTORY. NON-GEOLOGICAL readers will find in the following table a condensed explanation of the more important technical terms used in the following pages. The order is from older to newer. GREATER PERIODS. SYSTEMS OF FORMATIONS. CHARACTERISTIC FOSSILS. ARCHAEAN OR Eozoic Pre-Laurentian Laurentian Protozoa Protophyta PALAEOZOIC Huronian Cambrian Cambro- Silurian* Silurianf Devonian Carboniferous Permian 1 Crustaceans 1 Molluscs 1 Worms ( Corals, etc. Fishes Amphibians Algse Cryptogamous and Gymnospermous Plants. MESOZOIC Triassic Jurassic Cretaceous {Reptiles Birds Earliest Mammals Pines and Cycads . Trees of modern types. KAINOZOIC OR TERTIARY Eocene Miocene Pliocene Pleistocene Modern Higher Mammals of extinct forms Recent Mammals and Man. Modern Plants. * Ordovician of Lapworth. f Salopian of Lapworth. THE STARTING-POINT. DEDICATED TO THE MEMORY OF PROF. ROBERT JAMESON, OF THE UNIVERSITY OF EDINBURGH, MY FIRST TEACHER IN GEOLOGY, WHOSE LECTURES I ATTENDED, AND WHOSE KIND ADVICE AND GUIDANCE I ENJOYED, IN THE WINTER OF 1840-1841. S. E. HEADLANDS AND SPURS POPULAR PAPERS ON LEADING TOPICS REVISITING OLD LOCALITIES DEDICATIONS GENERAL SCOPE OF THE WORK CHAPTER I. THE STARTING-POINT. AN explorer trudging along some line of coast, or traversing some mountain region, may now and then reach a pro- jecting headland, or bold mountain spur, which may enable him to command a wide view of shore and sea, or of hill and valley, before and behind. On such a salient point he may sit down, note-book and glass in hand, and endeavour to cor- relate the observations made on the ground he has traversed, and may strain his eyes forward in order to anticipate the features of the track in advance. Such are the salient points in a scientific pilgrimage of more than half a century, to which I desire to invite the attention of the readers of these papers. In doing so, I do not propose to refer, except incidentally, to subjects which I have already discussed in books accessible to general readers, but rather to those which are imbedded in little accessible transactions, or scientific periodicals, or which have fallen out of print. I cannot therefore pretend to place the reader on all the salient points of geological science, or even on all of those I have myself reached, but merely to lead him to some of the viewing-places which I have found particu- larly instructive to myself. For similar reasons it is inevitable that a certain personal element shall enter into these reminiscences, though this auto- biographical feature will be kept as much in the background as possible. It is also to be anticipated that the same subject THE STARTING-POINT may appear more than once, but from different points of view, since it is often useful to contemplate certain features of the landscape from more than one place of observation. To drop the figure, the reader will find in these papers, in a plain and popular form, yet it is hoped not in a superficial manner, some of the more important conclusions of a geo- logical worker of the old school, who, while necessarily giving attention to certain specialties, has endeavoured to take a broad and comprehensive view of the making of the world in all its aspects. The papers are of various dates ; but in revising them for publication I have endeavoured, without materially changing their original form, to bring them up to the present time, and to state any corrections or changes of view that have com- mended themselves to me in the meantime. Such changes or modifications of view must of necessity occur to every geologi- cal worker. Sometimes, after long digging and hammering in some bed rich in fossils, and carrying home a bag laden with treasures, one has returned to the spot, and turned over the debris of previous excavation, with the result of finding some- thing rare and valuable, before overlooked. Or, in carefully trimming and chiselling out the matrix of a new fossil, so as to uncover all its parts, unexpected and novel features may develop themselves. Thus, if we were right or partially right before, our new experience may still enable us to enlarge our views or to correct some misapprehensions. In that spirit I have endeavoured to revise these papers, and while I have been able to add confirmations of views long ago expressed, have been willing to accept corrections and modifications based on later discoveries. In the somewhat extended span of work which has been allotted to me, I have made it my object to discover new facts, and to this end have spared no expenditure of time and labour ; but I have felt that the results of discoveries in the THE STARTING-POINT works of God should not be confined to a coterie, but should be made public for the benefit of all. Hence I have gladly embraced any opportunities to popularise my results, whether in lectures, articles, popular books, or in the instruction of students, and this in a manner to give accurate knowledge, and perhaps to attract the attention of fellow-workers to points which they might overlook if presented merely in dry and technical papers. These objects I have in view in connection with the present collection of papers, and also the fact that my own pilgrimage is approaching its close, and that I desire to aid others who may chance to traverse the ground I have passed over, or who may be preparing to pass beyond the point I have reached. To a naturalist of seventy years the greater part of life lies in the past, and in revising these papers I have necessarily had my thoughts directed to the memory of friends, teachers, guides, and companions in labour, who have passed away. I have therefore, as a slight token of loving and grateful remem- brance dedicated these papers to the memory of men I have known and loved, and who, I feel, would sympathise with me in spirit, in the attempt, however feeble, to direct attention to the variety and majesty of those great works of the Creator which they themselves delighted to study. Since the design of these papers excludes special details as to Canadian geology, or that of those old eastern countries to which I have given some attention, I must refer for them to other works, and shall append such reference of this kind as may be necessary. At the same time it will be observed that as my geological work has been concerned most largely with the oldest and newest rocks of the earth, and with the history of life rather than with rocks and minerals, there must neces- sarily be some preponderance in these directions, which might however, independently of personal considerations, be justified by the actual value of these lines of investigation, and by the THE STARTING-POINT special interest attaching to them in the present state of scien- tific discovery. Having thus defined my starting-point, I would now with all respect and deference ask the reader to accompany me from point to point, and to examine for himself the objects which may appear either near, or in the dim uncertain distance, in illustration of what the world is, and how it became what it is.^ Perhaps, in doing so, he may be able to perceive much more than I have been able to discover ; and if so, I shall rejoice, even if such further insight should correct or counteract some of my own impressions. It is not given to any one age or set of men to comprehend all the mysteries of nature, or to arrive at a point where it can be said, there is no need of farther exploration. Even in the longest journey of the most adven- turous traveller there is an end of discovery, and, in the study of nature, cape rises beyond cape and mountain behind moun- tain interminably. The finite cannot comprehend the infinite, the temporal the eternal. We need not, however, on that account be agnostics, for it is still true that, within the scope of our narrow powers and opportunities, the Supreme Intelli- gence reveals to us in nature His power and divinity ; and it is this, and this alone, that gives attraction and dignity to natural science. WORLD-MAKING. DEDICATED TO THE MEMORY OF ADAM SEDGWICK AND SIR RODERICK IMPEY MURCHISON, WHOSE JOINT LABOURS CAF.KISD OUR KNOWLEDGE OF THE HISTORY OF THE EARTH TWO STAGES FARTHER BACK, AND WHOSE DIFFERENCES OF OPINION SERVED TO RENDER MORE GLORIOUS THEIR VICTORIES. VISION OF A NASCENT WORLD THE OLDEST ROCKS DE- VELOPMENT OF LIFE FORMATION OF CONTINENTS IN WHAT SENSE PERMANENT AMERICA AS AN EXAMPLE CHAPTER II. WORLD-MAKING. EOLOGICAL reading, especially when of a strictly VJT uniformitarian character and in warm weather, some- times becomes monotonous ; and I confess to a feeling of drowsiness creeping over me when preparing material for a pre- sidential address to the American Association for the Advance- ment of Science in August, 1883. In these circumstances I became aware of the presence of an unearthly visitor, who announced himself as of celestial birth, and intimated to me that being himself free from those restrictions of space and time which are so embarrassing to earthly students, he was pre- pared for the moment to share these advantages with me, and to introduce me to certain outlying parts of the universe, where I might learn something of its origin and early history. He took my hand, and instantly we were in the voids of space. Turning after a moment, he pointed to a small star and said, "That is the star you call the sun ; here, you see, it is only about the third magnitude, and in a few seconds it will disappear." These few seconds, indeed, reduced the whole visible firma- ment to a mere nebulous haze like the Milky Way, and we seemed to be in blank space. But pausing for a moment I became aware that around us were multitudes of dark bodies, so black that they were, so to speak, negatively visible, even in the almost total darkness around. Some seemed large and massive, some a mere drift of minute particles, formless and without distinct limits. Some were swiftly moving, others 10 WORLD-MAKING stationary, or merely revolving on their own axes. It was a " horror of great darkness," and I trembled with fear. "This," said my guide, "is what the old Hebrew seer called tohu ve bohu, ' formless and void,' the * Tiamat ' or abyss of the old Chaldeans, the ' chaos and old night ' of the Greeks. Your mundane physicists have not seen it, but they speculate re- garding it, and occupy themselves with questions as to whether it can be lightened and vivified by mere attractive force, or by collision of dark bodies impinging on each other with vast momentum. Their speculations are vain, and lead to nothing, because they have no data wherefrom to calculate the in- finite and eternal Power who determined either the attraction or the motion, or who willed which portion of this chaos was to become cosmos, and which was to remain for ever dead and dark. Let us turn, however, to a more hopeful prospect." We sped away to another scene. Here were vast luminous bodies, such as we call nebulae. Some were globular, others disc-like, others annular or like spiral wisps, and some were composed of several concentric shells or rings. All were in rapid rotation, and presented a glo'rious and bril- liant spectacle. "This," said my guide, "is matter of the same kind with that we have just been considering ; but it has been set in active motion. The fiat ' Let there be light ! ' has been issued to it. Nor is its motion in vain. Each of these ne- bulous masses is the material of a system of worlds, and they will produce systems of different forms in accordance with the various shapes and motions which you observe. Such bodies are well known to earthly astronomers. One of them, the great nebula of Andromeda, has been photographed, and is a vast system of luminous rings of vapour placed nearly edgewise to the earth, and hundreds of times greater than the whole solar system. But now let us annihilate time, and consider these gigantic bodies as they will be in the course of many millions of years." Instantaneously these vast nebulae had concentrated WORLD- MAKING II themselves into systems of suns and planets, but with this difference from ours, that the suns were very large and sur- rounded with a wide luminous haze, and each of the planets was self-luminous, like a little sun. In some the planets were dancing up and down in spiral lines. In others they were moving in one plane. In still others, in every variety of direction. Some had vast numbers of little planets and satellites. Others had a few of larger size. There were even some of these systems that had a pair of central suns of con- trasting colours. The whole scene was so magnificent and beautiful that I thought I could never weary of gazing on it. " Here," said he, " we have the most beautiful condition of systems of worlds, when considered from a merely physical point of view : the perfection of solar and planetary luminousness, but which is destined to pass away in the interest of things more important, if less showy. This is the condition of the great star Sirius, which the old priest astronomers of the Nile Valley made so much of in their science and religion, and which they called Sothis. It is now known by your star- gazers to be vastly larger than your sun, and fifty times more brilliant. 1 Let us select one of these systems somewhat similar to the solar system, and suppose that the luminous atmospheres of its nearer planets are beginning to wane in brilliancy. Here is one of them, through whose halo of light we can see the body of the planet. What do you now per- ceive ?" The planet referred to was somewhat larger in appear- ance than our earth, and, approaching near to it, I could see that it had a cloud-bearing firmament, and that it seemed to have continents and oceans, though disposed in more regular forms than on our own planet, and with a smaller proportion of land. Looking at it more closely, I searched in vain for 1 In evidence of these and other statements I may refer to Huggins' recent address as President of the British Association, and to the " Story of the Heavens," etc., by Sir Robert Ball. 12 WORLD-MAKING any sign of animal life, but I saw a vast profusion of what might be plants, but not like those of this world. 1 These were trees of monstrous stature, and their leaves, which were of great size and shaped like fronds of seaweeds, were not usually green, but variegated with red, crimson and orange. The sur- face of the land looked like beds of gigantic specimens of Colias and similar variegated-leaved plants, the whole present- ing a most gorgeous yet grotesque spectacle. " This," said my guide, " is the primitive vegetation which clothes each of the planets in its youthful state. The earth was once so clothed, in the time when vegetable life alone existed, and there were no animals to prey upon it, and when the earth was, like the world you now look upon, a paradise of plants ; for all things in nature are at first in their best estate. This vegetation is known to you on the earth only by the Carbon and Graphite buried in your oldest rocks. It still lingers on your neighbour Mars, 2 which has, however, almost passed beyond this stage, and we are looking forward before long to see a still more gigantic though paler development of it in altogether novel shapes on the great continents that are being formed on the surface of Jupiter. But look again." And time being again annihilated, I saw the same world, now destitute of any luminous envelope, with a few dark clouds in its atmosphere, and presenting just the same appearance which I would sup- pose our earth to present to an astronomer viewing it with a powerful telescope from the moon. " Here we are at home again," said my guide; "good-bye." I found myself nodding over my table, and that my pen had just dropped from my hand, making a large blot on my paper. My dream, however, 1 We shall see farther on that there is reason to believe that the primitive land vegetation was more different from that of the Devonian and Carboni- ferous than it is from that of the present day. 2 Mars is probably a stage behind the earth in its development, and the ruddy hue of its continents would seem to be due to some organic covering. WORLD- MAKING 13 gave me a hint as to a subject, and I determined to devote my address to a consideration of questions which geology has not solved, or has only imperfectly and hypothetically dis- cussed. Such unsolved or partially solved questions must necessarily exist in a science which covers the whole history of the earth in time. At the beginning it allies itself with astronomy and physics and celestial chemistry. At the end it runs into human history, and is mixed up with archaeology and anthro- pology. Throughout its whole course it has to deal with questions of meteorology, geography and biology. In short, there is no department of physical or biological science, with which this many-sided study is not allied, or at least on which the geologist may not presume to trespass. When, therefore, it is proposed to discuss in the present chapter some of the unsolved problems and disputed questions of this universal science, the reader need not be surprised if it should be some- what discursive. Perhaps we may begin at the utmost limits of the subject by remarking that in matters of natural and physical science we are met at the outset with the scarcely solved question as to our own place in the nature which we study, and the bearing of this on the difficulties we encounter. The organism of man is decidedly a part of nature. We place ourselves, in this aspect, in the sub-kingdom vertebrata and class mammalia, and recognise the fact that man is the terminal link in a chain of being, extending throughout geological time. But the or- ganism is not all that belongs to man, and when we regard him as a scientific inquirer, we raise a new question. If the human mind is a part of nature, then it is subject to natural law, and nature includes mind as well as matter. Indeed, without being absolute idealists we may hold that mind is more potent than matter, and nearer to the real essence of things. Our science is in any case necessarily dualistic, being the product 14 WORLD-MAKING of the reaction of mind on nature, and must be largely sub- jective and anthropomorphic. Hence, no doubt, arises much of the controversy of science, and much of the unsolved diffi- culty. We recognise this when we divide science into that which is experimental, or depends on apparatus, and that which is observational and classificatory distinctions these which relate not so much to the objects of science as to our methods of pursuing them. This view also opens up to us the thought that the domain of science is practically boundless, for who can set limits to the action of mind on the universe, or of the universe on mind. It follows that science, as it exists at any one time, must be limited on all sides by unsolved mysteries ; and it will not serve any good purpose to meet these with clever guesses. If we so treat the enigmas of the sphinx nature, we shall surely be devoured. Nor, on the other hand, must we collapse into absolute despair, and resign ourselves to the confession of inevitable ignorance. It becomes us rather boldly to confront the unsolved questions of nature, and to wrestle with their difficulties till we master such as we can, and cheerfully leave those we cannot overcome to be grappled with by our successors. Fortunately, as a geologist, I do not need to invite attention to those transcendental questions which relate to the ultimate constitution of matter, the nature of the ethereal medium filling space, the absolute difference or identity of chemical elements, the cause of gravitation, the conservation and dissipation of energy, the nature of life, or the primary origin of bioplasmic matter. I may take the much more humble role of an in- quirer into the unsolved or partially solved problems which meet us in considering that short and imperfect record which geology studies in the rocky layers of the earth's crust, and which leads no farther back than to the time when a solid rind had already formed on the earth, and was already covered with an ocean. This record of geology covers but a small WORLD-MAKING 15 part of the history of the earth and of the system to which it belongs, nor does it enter at all into the more recondite problems involved ; still it forms, I believe, some necessary preparation at least to the comprehension of these. If we are to go farther back, we must accept the guidance of physicists rather than of geologists, and I must say that in this physical cosmology both geologists and general readers are likely to find themselves perplexed with the vagaries in which the most sober mathematicians may indulge. We are told that the original condition of the solar system was that of a vaporous and nebulous cloud intensely heated and whirling rapidly round, that it probably came into this condition by the impact of two dark solid bodies striking each other so violently, that they became intensely heated and resolved into the smallest possible fragments. Lord Kelvin attributes this impact to their being attracted together by gravitative force. Croll l argues that in addition to gravitation these bodies must have had a proper motion of great velocity, which Lord Kelvin thinks " enormously " improbable, as it would require the solid bodies to be shot against each other with a marvellously true aim, and this not in the case of the sun only, but of all the stars. It is rather more improbable than it would be to affirm that in the artillery practice of two opposing armies, cannon balls have thousands of times struck and shattered each other midway between the hostile batteries. The ques- tion, we are told, is one of great moment to geologists, since on the one hypothesis the duration of our system has amounted to only about twenty millions of years ; on the other, it may have lasted ten times that number. 2 In any case it seems a strange way of making systems of worlds, that they should result from the chance collision of multitudes of solid bodies 1 " Stellar Evolution." 2 Other facts favour the shorter time (Clarence King, Am. Jl. of Science > vol. xlv. , 3rd series). S. E. 2 1 6 WORLD-MAKING rushing hither and thither in space, and it is almost equally strange to imagine an intelligent Creator banging these bodies about like billiard balls in order to make worlds. Still, in that case we might imagine them not to be altogether aimless. The question only becomes more complicated when with Grove and Lockyer we try to reach back to an antecedent condition, when there are neither solid masses nor nebulae, but only an inconceivably tenuous and universally diffused medium made up of an embryonic matter, which has not yet even resolved itself into chemical elements. How this could establish any motion within itself tending to aggregation in masses, is quite inconceivable. To plodding geologists labori- ously collecting facts and framing conclusions therefrom, such flights of the mathematical mind seem like the wildest fan- tasies of dreams. We are glad to turn from them to examine those oldest rocks, which are to us the foundation stones of the earth's crust. What do we know of the oldest and most primitive rocks ? At this moment the question may be answered in many and discordant ways ; yet the leading elements of the answer may be given very simply. The oldest rock formation known to geologists is the Lower Laurentian, the Fundamental Gneiss, the Lewisian formation of Scotland, the Ottawa gneiss of Canada, the lowest Archaean crystalline rocks. This forma- tion, of enormous thickness, corresponds to what the older geologists called the fundamental granite, a name not to be scouted, for gneiss is only a stratified or laminated granite. Perhaps the main fact in relation to this old rock is that it is a gneiss ; that is, a rock at once bedded and crystalline, and having for its dominant ingredient the mineral orthoclase, a compound of silica, alumina and potash, in which are imbedded, as in a paste, grains and crystals of quartz and hornblende. We know very well from its texture and composition that it cannot be a product of mere heat, and being a bedded rock WORLD-MAKING I/ we infer that it was laid down layer by layer in the manner of aqueous deposits. On the other hand, its chemical com- position is quite different from that of the muds, sands and gravels usually deposited from water. Their special charac- ters are caused by the fact that they have resulted from the slow decay of rocks like these gneisses, under the operation of carbon dioxide and water, whereby the alkaline matter and the more soluble part of the silica have been washed away, leaving a residue mainly silicious and aluminous. Such more modern rocks tell of dry land subjected to atmospheric decay and rain-wash. If they have any direct relation to the old gneisses, they are their grandchildren, not their parents. On the contrary, the oldest gneisses show no pebbles or sand or limestone nothing to indicate that there was then any land undergoing atmospheric waste, or shores with sand and gravel. For all that we know to the contrary, these old gneisses may have been deposited in a shoreless sea, hold- ing in solution or suspension merely what it could derive from a submerged crust recently cooled from a state of fusion, still thin, and exuding here and there through its fissures heated waters and volcanic products. This, it may be observed here, is just what we have a right to expect, if the earth was once a heated or fluid mass, and if our oldest Laurentian rocks consist of the first beds or layers deposited upon it, perhaps by a heated ocean. It has been well said that " the secret of the earth's hot youth has been well kept." But with the help of physical science we can guess at an originally heat-liquefied ball with denser matter at its centre, lighter and oxidised matter at its surface. We can imagine a scum or crust form- ing at the surface ; and from what we know of the earth's in- terior, nothing is more likely to have constituted that slaggy 1 Carbon dioxide, the great agent in the decay of silicious rocks, must then have constituted a very much larger part of the atmosphere than at present. 1 8 WORLD-MAKING crust than the material of our old gneisses. As to its bedded character, this may have arisen in part from the addition of cooling layers below, in part from the action of heated water above, and in part from pressure or tension ; while, wherever it cracked or became broken, its interstices would be injected with molten matter from beneath. All this may be conjecture, but it is based on known facts, and is the only probable con- jecture. If correct, it would account for the fact that the gneissic rocks are the lowest and oldest that we reach in every part of the earth. In short, the fundamental gneiss of the Lower Laurentian may have been the first rock ever formed ; and in any case it is a rock formed under conditions which have not since re- curred, except locally. It constitutes the first and best example of those chemico-physical, aqueous or aqueo-igneous rocks, so characteristic of the earliest period of the earth's history. Viewed in this way the Lower Laurentian gneiss is probably the oldest kind of rock we shall ever know the limit to our backward progress, beyond which there remains nothing to the geologist except physical hypotheses respecting a cooling incan- descent globe. For the chemical conditions of these primitive rocks, and what is known as to their probable origin, I may refer to the writings of my friends, the late Dr. Sterry Hunt and, Dr. J. G. Bonney, to whom we owe so much of what is known of the older crystalline rocks 1 as well as of their literature, and the questions which they raise. My purpose here is to sketch the remarkable difference which we meet as we ascend into the Middle and Upper Laurentian. In the next succeeding formation, the middle part of the Laurentian of Logan, the Grenville series of Canada, we meet with a great and significant change. It is true we have still a predominance of gneisses which may have been formed in the 1 limit, "Essays on Chemical Geology"; Bonney, "Addresses to British Association and Geological Society of London, " WORLD- MAKING 1 9 same manner with those below them ; ,but we find these now associated with great beds of limestone and dolomite, which must have been formed by the separation of calcium and mag- nesium carbonates from the sea water, either by chemical pre- cipitation or by the agency of living beings. We have also quartzite, quartzose gneisses, and even pebble beds, which in- form us of sandbanks and shores. Nay, more, we have beds containing graphite which must be the residue of plants, and iron ores which tell of the deoxidation of iron oxide by organic matters. In short, here we have evidence of new factors in world-building, of land and ocean, of atmospheric decay of rocks, of deoxidizing processes carried on by vegetable life on the land and in the waters, of limestone-building in the sea. To afford material for such rocks, the old Ottawa gneiss must have been lifted up into continents and mountain masses by bendings and foldings of the original crust. Under the slow but sure action of the carbon dioxide dissolved in rainwater, its felspar had crumbled down in the course of ages. Its potash, soda, lime, magnesia, and part of its silica had been washed into the sea, there to enter into new combinations and to form new deposits. The crumbling residue of fine clay and sand had been also washed down into the borders of the ocean, and had been there deposited in beds. Thus the earth had entered into a new phase, which continues onward through the geological ages ; and I place in the reader's hands one key for unlocking the mystery of the world in affirming that this great change took place, this new era was inaugurated in the midst of the Laurentian period, the oldest of our great divisions of the earth's geological history. 1 1 I follow the original arrangement of Logan, who first defined this succession in the extensive and excellent exposures of these rocks in Canada. Elsewhere the subject has often been confused and mixed with local de- tails. The same facts, though sometimes under different names, are re- corded by the geologists of Scandinavia, l>ritain, and the United States, 20 WORLD- MA KING Was not this a fit period for the first appearance of life? should we not expect it to appear, independently of the evidence of the fact, so soon at least as the temperature of the ocean falls sufficiently low to permit its existence ? * I do not propose to enter here into that evidence. This we shall have occasion to consider in the sequel. I would merely say here that we should bear in mind that in this latter half of the Lower Laurentian, or if we so choose to style it, Middle Laurentian period, we have the conditions required for life in the sea and on the land ; and since in other periods we know that life was always present when its conditions were present, it is not unreasonable to look for the earliest traces of life in this forma- tion, in which we find, for the first time, the completion ot those physical arrangements which make life, in such forms of it as exist in the sea, possible. This is also a proper place to say something of the disputed doctrine of what is termed metamorphism, or the chemical and molecular changes which old rocks have undergone. The Laurentian rocks are undoubtedly greatly changed from their original state, more especially in the matters of crystalli- zation and the formation of disseminated minerals, by the action of heat and heated water. Sandstones have thus passed into quartzites, clays into slates and schists, limestones into mar- bles. So far, metamorphism is not a doubtful question ; but when theories of metamorphism go so far as to suppose an actual change of one element for another, they go beyond the bounds of chemical credibility ; yet such theories of meta- morphism are often boldly advanced and made the basis of important conclusions. Dr. Hunt has happily given the name *' metasomatosis " to this imaginary and improbable kind of and the acceptance of the conclusions of Nicol and Lapworth has served to bring even the rocks of the Highlands of Scotland more into line with those of Canada. 1 Dana states this at 180 F. for plants and 120 for animals. WORLD-MAKING 21 metamorphism. I would have it to be understood that, in speaking of the metamorphism of the older crystalline rocks, it is not to this metasomatosis that I refer, and that I hold that rocks which have been produced out of the materials decom- posed by atmospheric erosion can never by any process of metamorphism be restored to the precise condition of the Laurentian rocks. Thus, there is in the older formations a genealogy of rocks, which, in the absence of fossils, may be used with some confidence, but which does not apply to the more modern deposits, and which gives a validity to the use of mineral character in classifying older rocks which does not hold for later formations. Still, nothing in geology abso- lutely perishes, or is altogether discontinued ; and it is prob- able that, down to the present day, the causes which produced the old Laurentian gneiss may still operate in limited locali- ties. Then, however, they were general, not exceptional. It is further to be observed that the term gneiss is sometimes of wide and even loose application. Beside the typical orthoclase and hornblendic gneiss of the Laurentian, there are micaceous, quartzose, garnetiferous and many other kinds of gneiss ; and even gneissose rocks, which hold labradorite or anorthite in- stead of orthoclase, are sometimes, though not accurately, in-^ eluded in the term. The Grenville series, or Middle Laurentian, is succeeded by what Logan in Canada called the Upper Laurentian, and which other geologists have called the Norite or Norian series. Here we still have our old friends the gneisses, but somewhat peculiar in type, and associated with them are great beds and masses, rich in lime-felspar, the so-called labradorite and anorthite rocks. The precise origin of these is uncertain, but this much seems clear, namely, that they originated in circumstances in which the great limestones deposited in the Lower or Middle Lauren- tian were beginning to be employed in the manufacture, prob- ably by aqueo-igneous agencies, of lime-felspars. This proves 22 WORLD-MAKING the Norian rocks to be younger than the Lower Laurentian, and that, as Logan supposed, considerable earth movements had occurred between the two, implying lapse of time, while it is also evident that the folding and crumpling of the Lower Lau- rentian had led to great outbursts of igneous matter from below the crust, or from its under part. Next to the Laurentian, but probably after an interval, the rocks of which are yet scarcely known, we have the Huronian of Logan, a series much less crystalline and more fragmentary, and affording more evidence of land elevation and atmo- spheric and aqueous erosion than those preceding it. It has extensive beds of volcanic rock, great conglomerates, some of them made up of rounded fragments of Laurentian rocks, and others of quartz pebbles, which must have been the remains of rocks subjected to very perfect decay. The pure quartz-rocks tell the same tale, while slates and limestones speak also of chemical separation of the materials of older rocks. The Hu- ronian evidently tells of previous movements in the Lauren- tian, and changes which allowed the Huronian to be deposited along its shores and on the edges of its beds. Yet the Huronian itself is older than the Palaeozoic series, and affected by power- ful earth movements at an earlier date. Life existed in the waters in Huronian times. We have spicules of sponges in the limestone, and organic markings on the slaty beds ; but they are few, and their nature is uncertain. Succeeding the Huronian, and made up of its debris and that of the Laurentian, we have the great Cambrian series, that in which we first find undoubted evidence of abundant marine life, and which thus forms the first chapter in the great Palaeozoic book of the early history of the world. Here let it be observed we have at least two wide gaps in our history, marked by the crumpling up, first, of the Laurentian, and then of the Huronian beds. After what has been said, the reader will perhaps not be WORLD-MAKING 23 astonished that fierce geological battles have raged over the old crystalline rocks. By some geologists they are almost entirely explained away, or referred to igneous action, or to the alteration of ordinary sediments. Under the treatment of another school they grow to great series of Pre-Cambrian rocks, constituting vast systems of formations, distinguishable from each other chiefly by differences of mineral character. Facts and fossils are daily being discovered, by which these disputes will ultimately be settled. After the solitary appearance of Eozoon in the Laurentian, and of a few uncertain forms in the Huronian, we find our- selves, in the Cambrian, in the presence of a nearly complete invertebrate fauna of protozoa, polyps, echinoderms, mollusks and Crustacea, and this not confined to one locality merely, but apparently extended simultaneously throughout the ocean, over the whole world. This sudden incoming of animal life, along with the subsequent introduction of successive groups of invertebrates, and finally of vertebrate animals, furnishes one of the greatest unsolved problems of geology, which geologists were wont to settle by the supposition of successive creations. In the sequel I shall endeavour to set forth the facts as to this succession, and the general principles involved in it, and to show the insufficiency of certain theories of evolution suggested by biologists to give any substantial aid to the geologist in these questions. At present I propose merely to notice some of the general principles which should guide us in studying the development of life in geological time, and the causes which have baffled so many attempts to throw light on this obscure portion of our unsolved problems. It has been urged on the side ot rational evolution and there are both rational and irrational forms of this many-sided doctrine that this hypothesis does not profess to give an explanation of the absolute origin of life on our planet, or even of the original organization of a single cell, or of a simple mass 24 WORLD-MAKING of protoplasm, living or dead. All experimental attempts to produce by synthesis the complex albuminous substances, or to obtain the living from the non-living, have so far been fruitless, and indeed we cannot imagine any process by which such changes could be effected. That they have been effected we know, but the process employed by their maker is still as mysterious to us as it probably was to him who wrote the words : " And God said, Let the waters swarm with swarmers." How vast is the gap in our knowledge and our practical power implied in this admission, which must, however, be made by every mind not absolutely blinded by a superstitious belief in those forms of words which too often pass current as philosophy. But if we are content to start with a number of organisms ready made a somewhat humiliating start, however we still have to ask How do these vary so as to give new species ? It is a singular illusion, and especially in the case of men who profess to be believers in natural law, that variation may be boundless, aimless and fortuitous, and that it is by spontaneous selection from varieties thus produced that development arises. But surely the supposition of mere chance and magic is un- worthy of science. Varieties must have causes, and their causes and their effects must be regulated by some law or laws. Now it is easy to see that they cannot be caused by a mere innate tendency in the organism itself. Every organism is so nicely equilibrated that it has no such spontaneous tendency, except within the limits set by its growth and the law of its periodical changes. There may, however, be equilibrium more or less stable. I believe all attempts hitherto made have failed to account for the fixity of certain, nay, of very many, types throughout geological time, but the mere consideration that one may be in a more stable state of equilibrium than another, so far explains it. A rocking stone has no more spontaneous tendency to move than an ordinary boulder, but WORLD-MAKING 25 it may be made to move with a touch. , So it probably is with organisms. But if so, then the causes of variation are external, as in many cases we actually know them to be, and they must depend on instability with change in surroundings, and this so arranged as not to be too extreme in amount, and to operate in some determinate direction. Observe how remarkable the unity of the adjustments involved in such a supposition ! how superior they must be to our rude and always more or less unsuccessful attempts to produce and carry forward varieties and races in definite directions ! This cannot be chance. If it exists, it must depend on plans deeply laid in the nature of things, else it would be most monstrous magic and causeless miracle. Still more certain is this conclusion when we con- sider the vast and orderly succession made known to us by geology, and which must have been regulated by fixed laws, only a few of which are as yet known to us. Beyond these general considerations we have others of a more special character, based on palaeontological facts, which show how imperfect are our attempts as yet to reach the true causes of the introduction of genera and species. One is the remarkable fixity of the leading types of living beings in geological time. If, instead of framing, like Haeckel, fanciful phylogenies, we take the trouble, with Barrande and Gaudry, to trace the forms of life through the period of their existence, each along its own line, we shall be greatly struck with this, and especially with the continuous existence of many low types of life through vicissitudes of physical conditions of the most stupendous character, and over a lapse of time scarcely conceivable. What is still more remarkable is that this holds in groups which, within certain limits, are perhaps the most variable of all. In the present world no creatures are individually more variable than the protozoa; as, for example, the foraminifera and the sponges. Yet these groups are fundamentally the same, from the beginning of the Palaeo- 26 WORLD-MAKING zoic until now, and modern species seem scarcely at all to differ from specimens procured from rocks at least half-way back to the beginning of our geological record. If we suppose that the present sponges and foraniinifera are the descendants of those of the Silurian period, we can affirm that in all that vast lapse of time they have, on the whole, made little greater change than that which may be observed in variable forms at present. The same remark applies to other low animal forms. In types somewhat higher and less variable, this is almost equally noteworthy. The pattern of the venation of the wings of cockroaches, and the structure and form of land snails, gally-worms and decapod crustaceans were all settled in the Carboniferous age, in a way that still remains. So were the foliage and the fructification of club-mosses and ferns. If, at any time, members of these groups branched off, so as to lay the foundation of new species, this must have been a very rare and exceptional occurrence, and one demanding even some suspension of the ordinary laws of nature. We may perhaps be content on this question to say with Gaudry, 1 that it is not yet possible to " pierce the mystery that surrounds the development of the great classes of animals," or with Prof. Williamson, 2 that in reference to fossil plants " the time has not yet arrived for the appointment of a botanical King-at-arms and Constructor of pedigrees." W r e shall, how- ever, find that by abandoning mere hypothetical causes and carefully noting the order of the development and the causes in operation, so far as known, we may reach to ideas as to cause and mode, and the laws of succession, even if unable to pene- trate the mystery of origins. Another caution which a palaeontologist has occasion to give with regard to theories of life, has reference to the tendency of biologists to infer that animals and plants were introduced 1 " Enchainements da Monde Animal/' Paris, 1883. 2 Address before Royal Institution, Feb., 1883. WORLD-MAKING under embryonic forms, and at first in few and imperfect species. Facts do not substantiate this. The first appearance of leading types of life is rarely embryonic, or of the nature of immature individuals. On the contrary, they often appear in highly perfect and specialized forms, often, however, of compo- site type and expressing characters afterwards so separated as to belong to higher groups. The trilobites of the Cambrian are some of them of few segments, and so far embryonic, but the greater. part are many-segmented and very complex. The batrachians of the Carboniferous present many characters higher than those of their modern successors and now appropriated to the true reptiles. The reptiles of the Permian and Trias usurped some of the prerogatives of the mammals. The ferns, lycopods and equisetums of the Devonian and Carboniferous were, in fructification, not inferior to their modem representa- tives, and in the structure of their stems far superior. The shell-bearing cephalopods of the Palaeozoic would seem to have possessed structures now special to a higher group, that of the cuttle-fishes. The bald and contemptuous negation of these facts by Haeckel and other biologists does not tend to give geologists much confidence in their dicta. Again, we are now prepared to say that the struggle for existence, however plausible as a theory, when put before us in connection with the productiveness of animals and the few survivors of their multitudinous progeny, has not been the determining cause of the introduction of new species. The periods of rapid introduction of new forms of marine life were not periods of struggle, but of expansion those periods in which the submergence of continents afforded new and large space for their extension and comfortable subsistence. In like manner, it was continental emergence that afforded the oppor- tunity for the introduction of land animals and plants. Fur- ther, in connection with this, it is now an established conclusion, that the great aggressive faunas and floras- of the continents. 28 WORLD-MAKING have originated in the north, some of them within the arctic circle, and this in periods of exceptional warmth, when the perpetual summer sunshine of the arctic regions coexisted with a warm temperature. The testimony of the rocks thus is that not struggle but expansion furnished the requisite conditions for new forms of life, and that the periods of struggle were characterized by depauperation and extinction. But we are sometimes told that organisms are merely mechanical, and that the discussions respecting their origin have no significance any more than if they related to rocks or crystals, because they relate merely to the organism considered as a machine, and not to that which may be supposed to be more important, namely, the great determining power of mind and will. That this is a mere evasion by which we really gain nothing, will appear from a characteristic extract of an article by an eminent biologist in the new edition of the Encyclopedia Britannica, a publication which, I am sorry to say, instead of its proper role as a repertory of facts, has admitted partisan papers, stating extreme and unproved speculations as if they were conclusions of science. The statement referred to is as follows : " A mass of living protoplasm is simply a molecular machine of great complexity, the total results of the working of which, or its vital phenomena, depend on the one hand on its construction, and on the other, on the energy supplied to it ; and to speak of vitality as anything but the name for a series of operations is as if one should talk of the horologity of a clock." It would, I think, scarcely be possible to put into the same number of words a greater amount of unscientific assumption and unproved statement than in this sentence. Is " living protoplasm " different in any way from dead protoplasm, and if so, what causes the difference ? What is a " machine " ? Can we conceive of a self-produced or uncaused machine, or one not intended to work out some definite results ? The results of the machine in question are said to be " vital phenomena " : WORLD-MAKING 29 certainly most wonderful results, and greater than those of any machine man has yet been able to construct. But why " vital " ? If there is no such thing as life, surely they are merely physical results. Can mechanical causes produce other than physical effects ? To Aristotle life was " the cause of form in organ- isms." Is not this quite as likely to be true as the converse pro- position ? If the vital phenomena depend on the " construction " of the machine, and the " energy supplied to it," whence this construction and whence this energy ? The illustration of the clock does not help us to answer this question. The construc- tion of the clock depends on its maker, and its energy is de- rived from the hand that winds it up. If we can think of a clock which no one has made, and which no one winds, a clock constructed by chance, set in harmony with the universe by chance, wound up periodically by chance, we shall then have an idea parallel to that of an organism living, yet without any vital energy or creative law ; but in such a case we should certainly have to assume some antecedent cause, whether we call it " horologity " or by some other name. Perhaps the term evolution would serve as well as any other, were it not that common sense teaches that nothing can be spontaneously evolved out of that in which it did not previously exist. There is one other unsolved problem in the study of life by the geologist to which it is still necessary to advert. This is the inability of palaeontology to fill up the gaps in the chain of being. In this respect we are constantly taunted with the im- perfection of the record, a matter so important that it merits a separate treatment; but facts show that this is much more complete than is generally supposed. Over long periods of time and many lines of being we have a nearly continuous chain, and if this does not show the tendency desired, the fault is as likely to be in the theory as in the record. On the other hand, the abrupt and simultaneous appearance of new types in many specific and generic forms and over wide and 30 WORLD-MAKING separate areas at one and the same time, is too often repeated to be accidental. Hence palaeontologists, in endeavouring to establish evolution, have been obliged to assume periods of exceptional activity in the introduction of species, alternating with others of stagnation, a doctrine differing very little from that of special creation, as held by the older geologists. The attempt has lately been made to account for these breaks by the assumption that the geological record relates only to periods of submergence, and gives no information as to those of elevation. This is manifestly untrue. In so far as marine life is concerned, the periods of submergence are those in which new forms abound for very obvious reasons, already hinted ; but the periods of new forms of land and fresh-water life are those of elevation, and these have their own records and monuments, often very rich and ample, as, for example, the swamps of the Carboniferous, the transition from the great Cretaceous sub- sidence, when so much of the land of the Northern Hemisphere was submerged, to the new continents of the Tertiary, the Tertiary lake-basins of Western America, the Terraces and raised beaches of the Pleistocene. Had I time to refer in detail to the breaks in the continuity of life which cannot be explained by the imperfection of the record, I could show at least that nature in this case does advance per saltum by leaps, rather than by a slow continuous process. Many able reasoners, as Le-Conte, in America, and Mivart and Collard in England, hold this view. Here, as elsewhere, a vast amount of steady conscientious work is required to enable us to solve the problems of the history of life. But if so, the more the hope for the patient student and investigator. I know nothing more chilling to re- search, or unfavourable to progress, than the promulgation of a dogmatic decision that there is nothing to be learned but a merely fortuitous and uncaused succession, amenable to no law, and only to be covered, in order to hide its shapeless and WORLD-MAKING 3! uncertain proportions, by the mantle 'of bold and gratuitous hypothesis. So soon as we find evidence of continents and oceans we raise the question, Have these continents existed from the first in their present position and form, or have the land and water changed places in the course of geological time ? This ques- tion also deserves a separate and more detailed consideration. In reality both statements are true in a certain limited sense. On the one hand, any geological map whatever suffices to show that the general outline of the existing land began to be formed in the first and oldest crumplings of the crust. On the other hand, the greater part of the surface of the land consists of marine sediments which must have been deposited when the continents were in great part submerged, and whose materials must have been derived from land that has perished in the process, while all the continental surfaces, except, perhaps, some high peaks and ridges, have been many times submerged. Both of these apparently contradictory statements are true ; and without assuming both, it is impossible to explain the existing contours and reliefs of the surface. In exceptional cases even portions of deep sea have been elevated, as in the case of the Polycistine deposits in the West Indies ; but these exceptions are as yet scarcely sufficient to prove the rule. In the case of North America, the form of the old nucleus of Laurentian rock in the north already marks out that of the finished continent, and the successive later formations have been laid upon the edges of this, like the successive loads of earth dumped over an embankment. But in order to give the great thickness of the Palaeozoic sediments, the land must have been again and again submerged, and for long periods of time. Thus, in one sense, the continents have been fixed ; in another, they have been constantly fluctuating. Hall and Dana have well illustrated these points in so far as eastern North America s. E. 3 32 WORLD-MAKING is concerned. Prof. Hull of the Geological Survey of Ireland has had the boldness to reduce the fluctuations of land and water, as evidenced in the British Islands, to the form of a series of maps intended to show the physical geography of each successive period. The attempt is probably premature, and has been met with much adverse criticism ; but there can be no doubt that it has an element of truth. When we attempt to calculate what could have been supplied from the old Eozoic nucleus by decay and aqueous erosion, and when we take into account the greater local thickness of sediments towards the present sea-basins, we can scarcely avoid the conclusion that extensive areas once occupied by high land are now under the sea. But to ascertain the precise areas and position of these perished lands may now be impossible. In point of fact we are obliged to believe in the contempo- raneous existence in all geological periods, except perhaps the very oldest, of three sorts of areas on the surface of the earth : (i) Oceanic areas of deep sea, which must always have oc- cupied the bed of the present ocean, or parts of it ; (2) Conti- nental plateaus sometimes existing as low flats, or as higher table-lands, and sometimes submerged ; (3) Areas of plication or folding, more especially along the borders of the oceans, forming elevated lands rarely submerged and constantly afford- ing the material of sedimentary accumulations. We shall find, however, that these have changed places in a remarkable man- ner, though always in such a way that neither the life of the land nor of the waters was wholly extinguished in the process. Every geologist knows the contention which has been occasioned by the attempts to correlate the earlier Palaeozoic deposits of the Atlantic margin of North America with those forming at the same time on the interior plateau, and with those of intervening lines of plication and igneous disturbance. Stratigraphy, lithology and fossils are all more or less at fault in dealing with these questions, and while the general nature WORLD-MAKING 33 of the problem is understood by many geologists, its solution in particular cases is still a source of apparently endless debate. The causes and mode of operation of the great movements of the earth's crust which have produced mountains, plains and table-lands, are still involved in some mystery. One patent cause is the unequal settling of the crust towards the centre ; but it is not so generally understood as it should be, that the greater settlement of the ocean-bed has necessitated its pressure against the sides of the continents in the same manner that a huge ice-floe crushes a ship or a pier. The geological map of North America shows this at a glance, and impresses us with the fact that large portions of the earth's crust have not only been folded but bodily pushed back for great distances. On looking at the extreme north, we see that the great Laurentian mass of central Newfoundland has acted as a projecting pier to the space immediately west of it, and has caused the gulf of St. Lawrence to remain an undisturbed area since Palaeozoic times. Immediately to the south of this, Nova Scotia and New Brunswick are folded back. Still farther south, as Guyot has shown, the old sediments have been crushed in sharp folds against the Adirondack mass, which has sheltered the table-land of the Catskills and of the great lakes. South of this again the rocks of Pennsylvania and Maryland have been driven back in a great curve to the west. Move- ments of this kind on the Pacific coast of America have been still more stupendous, as well as more recent. Dr. G. M. Dawson * thus refers to the crushing action of the Pacific bed on the rocks of British Columbia, and this especially at two periods, the close of the Triassic and the close of the Cretace- ous : " The successive foldings and crushings which the Cor- dillera region has suffered have resulted in an actual change of position of the rocks now composing its western margin. 1 Trans. Royal Society of Canada, 1890. 34 WORLD-MAKING This change may have amounted since the beginning of Mesozoic time to one-third of its whole present width, which would place the line of the coast ranges about two degrees of longitude farther west." Here we have evidence that a tract of country 400 miles wide and consisting largely of mountain ranges and table-lands, has been crushed bodily back over two degrees of longitude ; and this applies not to British Columbia merely, but to the whole west coast from Alaska to Chili. Yet we know that any contraction of the earth's nucleus can crumple up only a very thin superficial crust, which in this case must have slid over the pasty mass below. 1 Let it be observed, however, that the whole lateral pressure of vast areas has been condensed into very narrow lines. Nothing, I think, can more forcibly show the enormous pressure to which the edges of the continents have been exposed, and at the same time the great sinking of the hard and resisting ocean- beds. Complex and difficult to calculate though these move- ments of plication are, they are more intelligible than the apparently regular pulsations of the flat continental areas, whereby they have alternately been below and above the waters, and which must have depended on somewhat regularly recurring causes, connected either with the secular cooling of the earth or with the gradual retardation of its rotation, or with both. There is, however, good reason to believe that the suc- cessive subsidences alternated with the movements of plication, and depended on upward bendings of the ocean floor, and also on the gradual slackening of the rotation of the earth. Throughout these changes, each successive elevation exposed the rocks for long ages to the decomposing influence of the atmosphere. Each submergence swept away and deposited as 1 This view is quite consistent with the practical solidity of the earth, and vvith the action of local expansion by heat, of settlement of areas overloaded with sediment, and of primitive or downward sliding of beds, This we shall see in the sequel. - WORLD-MAKING 35 sediment the material accumulated by decay. Every change of elevation was accompanied with changes of climate, and with' modifications of the habitats of animals and plants. Were it possible to restore accurately the physical geography of the earth in all these respects, for each geological period, the data for the solution of many difficult questions would be furnished. We have wandered through space and time sufficiently for one chapter, and some of the same topics must come up later in other connections. Let us sum up in a word. In human history we are dealing with the short lives and limited plans of man. In the making of worlds we are conversant with the plans of a Creator with whom one day is as a thousand years, and a thousand years as one day. We must not measure such things by our microscopic scale of time. Nor should we fail to see that vast though the ages of the earth are, they are parts of a continuous plan, and of a plan probably reaching in space and time immeasurably beyond our earth. When we trace the long history from an incandescent fire-mist to a finished earth, and vast ages occupied by the dynasties of plant and animal life, we see not merely a mighty maze, an almost endless pro- cession of changes, but that all of these were related to one another by a chain of causes and effects leading onward to greater variety and complexity, while retaining throughout the traces of the means employed. The old rocks and the ancient lines of folding and the perished forms of life are not merely a scaffolding set up to be thrown down, but the foundation stones of a great and symmetrical structure. Is it yet conv pleted ? Who can tell ? The earth may still be young, and infinite ages of a better history may lie before it. REFERENCES l : Presidential Address to the American Association for the Advancement of Science, meeting at Minneapolis, 1883. "The Story of the Earth and Man." Ninth edition, London, 1887. 1 The references in this and succeeding chapters are exclusively to papers and works by the author, on which the several chapters are based. THE IMPERFECTION OF THE GEOLOGICAL RECORD. DEDICATED TO THE MEMORY OF JOACHIN BARRANDE, ONE OF THE MOST SUCCESSFUL LABOURERS IN THE COMPLETION OF THE HISTORY OF LIFE IN ITS EARLIER STAGES. NATURE OF THE IMPERFECTION QUESTIONS AS TO ITS ARISING FROM WANT OF CONTINUITY, FROM LACK OF PRESERVATION, FROM IMPERFECT COLLECTING. EX- AMPLESLAND SNAILS, CARBONIFEROUS BATRACHIANS, PALAEOZOIC SPONGES, PLEISTOCENE SHELLS, DEVONIAN AND CARBONIFEROUS PLANTS COMPARATIVE PERFEC- TION IN THE CASE OF MARINE SHELLS, ETC. POSSIBLE CAMBRIAN SQUIDS QUESTIONS AS TO WANT OF FIRST CHAPTERS OF THE RECORD PRACTICAL CONCLUSIONS CHAPTER III. THE IMPERFECTION OF THE GEOLOGICAL RECORD. /COMPLAINTS of the imperfection of the geological V_^/ record are rife among those biologists who expect to find continuous series of fossils representing the gradual trans- mutation of species. No doubt these gaps are in some cases portentous, and unfortunately they often occur just where it is most essential to certain general conclusions that they should be filled up. Instead, however, of making vague lamentations on the subject, it is well to inquire to what causes these gaps may be due, to what extent they invalidate the completeness of geological history for scientific purposes, and how they may best be filled. Here we may first remark that it is not so much the physical record of geology that is imperfect as the organic record. Ever since the time of Hutton and Playfair we have learned that the processes of mineral detrition and deposition are contin- uous, and have been so throughout geological time. The erosion of the land is constantly going on, every shower carries its tribute of earthy matter toward the sea, and every wave that strikes against a beach or cliff does some work toward the grinding of shells, pebbles or stone. Thus, everywhere around our continents there is a continuous deposition of beds of earthy matter, and it is this which, when elevated into new land, has given us our chronological series of geological forma- tions. True, the elevating process is not continuous, but, so 39 40 IMPERFECTION OF THE GEOLOGICAL RECORD far as we know, intermittent ; but it has been so often repeated that we have no reason to doubt that the wasting continents afford a complete series of aqueous deposits, since the time when the dry land first appeared. In recent years the Challenger expedition and similar dredg- ings have informed us of still another continuity of deposition in the depths of the ocean. There, where no detritus from the land, or only a very little fine volcanic ash or pumice has ever reached, we have, going on from age to age, a deposit of the hard parts of abyssal animals and of those that swim in the open sea ; so that if it were possible to bore or sink a shaft in some parts of the ocean, we should find not only a continu- ous bed, but a continuous series of pelagic life from the Laurentian to the present day. Thus we have continuous physical records, could we but reach or completely put them together, and eliminate the disturbing influence of merely local vicissitudes. It is when we begin to search the geological formations for fossils, that imperfection in our record first becomes painfully manifest. In the case of many groups of marine animals, as, for example, the shell-fish and the corals, and I may add the bivalve crustaceans, so admirably worked up by my friend Prof. Rupert Jones, we have very complete series. With the land snails the case is altogether different. As stated in an- other paper of this series, a few species of these animals appear in the later Palaeozoic age, and after that they have no suc- cessors known to us in all the great periods covered by the Permian, the Trias, and the earlier Jurassic. A few air-breath- ing water-snails appear in the upper Jurassic, and true land snails are not met with again until the Tertiary. Were there no land snails in this vast lapse of time ? Have we two suc- cessive creations, so to speak, of these creatures at distant intervals ? Were they only diminished in numbers and distri- bution in the intervening time? Is the hiatus owing merely IMPERFECTION OF THE GEOLOGICAL RECORD 41 to the unlikelihood of such shells being preserved ? Or is it owing to the lack of diligence and care in collecting ? In this particular case we are, no doubt, disposed to say that the series must have been continuous. But we cannot be sure of this. In whatever way a few species of land snails were so early introduced in the time of the Devonian or of the Coal formation, if from physical vicissitudes or lack of proper pabulum they became extinct, there is no reason known to us why, when circumstances again became favourable, they should not be reintroduced in the same manner as at first, whether by development from allied types or otherwise. The fact that the few Devonian and Carboniferous species are very like those that still exist, perhaps makes against this supposition, but does not exclude it. If we suppose that new forms of life of low grade are introduced from time to time in the course of the geological ages, and if we adopt the Darwinian hypo- thesis of evolution, we arrive, as Naegeli has so well pointed out, at the strange paradox, that the highest forms of life must be the oldest of all, since they will be the descendants of the' earliest of the lower animals, whereas the animals now of low grade may have been introduced later, and may not have had time to improve. But all our attempts to reduce nature to one philosophic expression necessarily lead to such paradoxes. On the other hand, the chances of the preservation of land snails in aqueous deposits are vastly less than those in favour of the preservation of aquatic species. The first Carboniferous species found 1 had been preserved in the very exceptional circumstances afforded by the existence of hollow trunks of Sigillariae on the borders of the Coal formation flats, and the others subsequently found were in beds no doubt receiving the drainage of neighbouring land areas. Still it is not un- common on the modern sea-shore, anywhere near the mouths of rivers, to find a few freshwater shells here and there. The 1 Piipa vetusta of the Nova Scotia coal formation. 42 IMPERFECTION OF THE GEOLOGICAL RECORD carbonaceous beds of the Trias, the fossil soils of the Portland series, the estuarine Wealden beds would seem to be as favour- ably situated as those of the coal formation for preserving land shells, though possibly the flora of the Mesozoic was less suit- able for feeding such creatures than that of the Coal period, and they may consequently have become few and local. After all, perhaps more diligent collecting and more numerous col- lectors might succeed, and may succeed in the future, in filling this and similar gaps. It is a great mistake to suppose that discoveries of this kind are made by chance. It is only by the careful and painstaking examination of much material that the gaps in the geological record can be filled up, and I propose in the sequel of this article to note a few instances, in a country where the range of territory is altogether out of proportion to the number of observers, and which have come within my own knowledge. It was not altogether by accident that Sir C. Lyell and the writer discovered a few reptilian bones and a land snail in breaking up portions of the material filling an erect Sigillaria in the South Joggins coal measures. We were engaged in a deliberate survey of the section, to ascertain as far as might be the conditions of accumulation of coal, and one point which occurred to us was to inquire as to the circumstances of preservation of stumps of forest trees in an erect position, to trace their roots into the soils on which they stood, and to ascertain the circumstances in which they had been buried, had decayed, and had been filled with mineral matter. It was in questioning these erect trees on such subjects and this not without some digging and hammering that we made the dis- covery referred to. But we found such remains only in one tree, and they were very imperfect, and indicated only two species of batrachians and one land snail. There the discovery might have rested. But I undertook to follow it up. In successive visits to the IMPERFECTION OF THE GEOLOGICAL RECORD 43 coast, a large number of trees standing in the cliff and reefs, or fallen to the shore, were broken up and examined, the result being to discover that, with one unimportant exception, the productive trees were confined to one of the beds at Coal Mine Point, that from which the original specimens had been obtained. Attention was accordingly concentrated on this, and as many as thirty trees were at different times extracted from it, of which rather more than one-half proved more or less productive. By these means bones representing about sixty specimens and twelve species were extracted, besides numerous remains of land shells, millipedes, and scorpions. In this way a very complete idea was obtained of the land life, or at least of the smaller land animals, of this portion of the coal formation of Nova Scotia. It is not too much to say that if similar repositories could be found in the succeeding forma- tions, and properly worked when found, our record of the history of land quadrupeds might be made very complete. When in 1855 I changed my residence from Nova Scotia to Montreal, and so was removed to some distance from the carboniferous rocks which I had been accustomed to study, I naturally felt somewhat out of place in a Cambro-Silurian dis- trict, more especially as my friend Billings had already almost exhausted its fossils. I found, however, a congenial field in the Pleistocene shell beds; more especially as I had given some attention to recent marine animals when on the sea coast. The very perfect series of Pleistocene deposits in the St. Lawrence valley locally contain marine shells from the bottom of the till or boulder clay up to the overlying sands and gravels. The assemblage was a more boreal one than that on the coast of Nova Scotia, though many of the species were the same, and both the climatal and bathymetrial conditions differed in different parts of the Pleistocene beds themselves. The gap in the record here could at that time be filled up only by col- lecting recent shells. In addition to what could be obtained 44 IMPERFECTION OF THE GEOLOGICAL RECORD by exchanging with naturalists who had collected in Greenland, Labrador, and Norway, I employed myself, summer after summer, in dredging both on the south and north shore of the St. Lawrence, until able at length to discover in a living state, but under different conditions as to temperature and depth, nearly every species found in trie beds on the land, from the lower boulder clay to the top of the formation, and from the sea-level to the beds six hundred feet high on the hills. Not only so : I could ascertain in certain places and conditions all the peculiar varieties of the species, and the special modes of life which they indicated. Thus, in the cases of the Peter Redpath Museum, and in notes on the Post- pliocene of Canada, the gap between the Modern and the Glacial age was completely filled up in so far as Canadian marine species are concerned. The net result was, as I have elsewhere stated, that no change other than varietal had occurred. In studying the fossil plants of the Carboniferous, so abundant in the fine exposures of the coal formation in Nova Scotia, two defects struck me painfully. One was the fragmentary and imperfect state of the specimens procurable. Another was the question, What preceded these plants in the older rocks ? The first of these was to be met only by thorough exploration. When a fragment of a plant was disclosed it was necessary to inquire if more existed in the same bed, and to dig, or blast away or break up the rock, until some remaining portions were disclosed. In this way it has been possible to obtain entire specimens of many trees of the Carboniferous ; and to such an extent has the laborious and somewhat costly process been effectual, that more species of carboniferous trees are probably known in their entire forms from the Coal forma- tions of Nova Scotia than from any other part of the world. I have been amused to find that so little are experiences of this kind known to some of my confreres abroad, that they IMPERFECTION OF THE GEOLOGICAL RECORD 45 are disposed to look with scepticism on the information obtained by this laborious but certain process, and to suppose that they are being presented with imaginary " restorations." I think it right here to copy a remark of a German botanist, who has felt himself called to criticise my work : " Dawson's description of the genus (Psilophyton) rests chiefly on the impression made on him in his repeated researches," etc. " He puts us off with an account of the general idea which he has drawn from the study of them." This is the remark of a closet naturalist, with reference to the kind of work above referred to, which, of course, cannot be represented in its entirety in figures or hand specimens. 1 As to the precursors of the Carboniferous flora, in default of information already acquired, I proceeded to question the Erian or Devonian rocks of Canada, in which Sir William Logan had already found remains of plants which had not, however, been studied or described. Laboriously coasting along the cliffs of Gaspe and the Baie des Chaleurs, digging into the sandstones of Eastern Maine, and studying the plants collected by the New York Survey, I began to find that there was a rich Devonian flora, and that, like that of the Carboni- ferous, it presented different stages from the base to the summit of the formation. But here a great advance was made in a somewhat unexpected way. My then young friends, the late Prof. Hartt and Mr. Matthew, of St. John, had found a few remains of plants in the Devonian, or at least pre-Carboniferous beds of St. John, which were placed in my hands for descrip- tion. They were so novel and curious that inquiry was stimu- lated, and these gentlemen, with some friends of similar tastes, explored the shales exposed in the reefs near St. John, and when they found the more productive beds, broke them up by 1 Solms-Laubach, " Fossil Botany." A pretentious book, which should not have been translated into English without thorough revision and correction. S. E. 4 46 IMPERFECTION OF THE GEOLOGICAL RECORD actual quarrying operations in such a way that they soon obtained the richest Devonian plant collections ever known. I think I may truly say that these young and enthusiastic explorers worked the St. John plant-beds in a manner pre- viously unexampled in the world. Their researches were not only thus rewarded, but incidentally they discovered the first known Devonian insects, which could not have been found by a less painstaking process, and one of them discovered what I believe to be the oldest known land shell. Still more, their studies led to the separation from the Devonian beds of the Underlying Cambrian slates, previously confounded with them ; and this, followed up by the able and earnest work of Mr. Matthew, has carried back our knowledge of the older rocks in Canada several stages, or as far as the earliest Cambrian previously known in Europe, but not before fully recognised in America, and has discovered in these old rocks the precursors of many forms of life not previously traced so far back. The moral of these statements of fact is that the imper- fections of the record will yield only to patient and painstaking work, and that much is in the power of local amateurs. I would enforce this last statement by a reference to a little research, in which I have happened to take part at a summer resort on the Lower St. Lawrence, at which I have from time to time spent a few restful vacation weeks. Little Metis is on the Quebec Group of Sir William Logan, that peculiar local representative of the lower part of the Cambro-Silurian and Upper Cambrian formations which stretches along the south side of the St. Lawrence all the way from Quebec to Cape Rosier, near Gaspe*, a distance of five hundred miles. This great series of rocks is a jumble of deposits belonging at that early time to the marginal area of what is now the American continent, and indicating the action not merely of ordinary causes of aqueous deposit, but of violent volcanic ejections, IMPERFECTION OF THE GEOLOGICAL RECORD 4? accompanied perhaps by earthquake waves, and not improb- ably by the action of heavy coast ice. The result is that mud rocks now in the form of black, grey, and red shales arid slates alternate with thick and irregular beds of hard sandstone, sometimes so coarse that it resembles the angular debris of the first treatment of quartz in a crusher. With these sandstones are thick and still more irregular conglomerates formed of pebbles and boulders of all sizes, up to several feet in diameter, some of which are of older limestones containing Cambrian fossils, while others are of quartzite or of igneous or volcanic rocks. The whole formation, as presented at Metis, is of the most unpromising character as regards fossils, and after visiting the place for ten years, and taking many long walks along the shore and into the interior, and scrutinising every exposure, I had found nothing more interesting than a few fragments of graptolites, little zoophytes, ancient representatives of our sea mosses, and which are quite characteristic of several portions of the Quebec Group. With these were some marks of fucoids and tracks or burrows of worms. The explorers of the Geological Survey had been equally unsuccessful. Quite accidentally a new light broke upon these unpromis- ing rocks. My friend, Dr. Harrington, strolling one day on the shore, sat down to rest on a stone, and picked up a piece of black slate lying at his feet. He noticed on it some faintly traced lines which seemed peculiar. He put it in his pocket and showed it to me. On examination with a lens it proved to have on it a few spicules of a hexactinellid sponge little crosses forming a sort of mesh or lattice-work similar to that which Salter had many years before found in the Cambrian rocks of Wales, and had named Protospongia the first sponge. The discovery seemed worth following up, and we took an early opportunity of proceeding to the place, where, after some search, we succeeded in tracing the loose pieces to a ledge of 48 IMPERFECTION OF THE GEOLOGICAL RECORD shale on the beach, where there was a little band, only about an inch thick, stored with remains of sponges, a small bivalve shell and a slender branching seaweed. This was one small layer in reefs of slate more than one hundred feet thick. We sub- sequently found two other thin layers, but less productive. Tools and workmen were procured, and we proceeded to quarry in the reef, taking out at low tide as large slabs as possible of the most productive layer, and carefully splitting these up. The results, as published in the Transactions of the Royal Society of Canada, 1 show more than twelve species of siliceous sponges belonging to six genera, besides fragments indicating other species, and all of these living at one time on a very limited space of what is practically a single surface of muddy sea-bottom. 2 The specimens show the parts of these ancient sponges much more perfectly than they were previously known, and indeed, enable many of them to be perfectly re- stored. They for the first time connect the modern siliceous sponges of the deep sea with those that flourished on the old sea-bottom of the early Cambro-Silurian, and thus bridge over a great gap in the histojy of this low form of life, showing that the principles of construction embodied in the remarkable and beautiful siliceous sponges, like Euplectella, the " Venus flower-basket," now dredged from the deep sea, were already perfectly carried out in this far-back beginning of life. This little discovery further indicates that portions of the older Palaeozoic sea-bottoms were as well stored with a varied sponge life as those of any part of the modern ocean. I figure 3 a number of species, remains of all of which may be gathered from a few yards of a single surface at Little Metis. The multitude of interesting details embodied in all this it is impossible to enter into here, but may be judged of from 1 Additional collections made in 1892 show two or three additional species, one of them the type of a new and remarkable genus. 2 1889, section iv. p. 39. 3 Frontispiece to chapter. IMPERFECTION OF THE GEOLOGICAL RECORD 49 the forms reproduced. These examples tend to show that the imperfection of the record may not depend on the record itself, but on the incompleteness of our work. We must make large allowance for imperfect collecting, and especially for the too prevalent habit of remaining content with few and incomplete specimens, and of grudging the time and labour necessary to explore thoroughly the contents of special beds, and to work out all the parts of forms found more or less in fragments. The point of all this at present is that patient work is needed to fill up the breaks in our record. A collector passing along the shore at Metis might have picked up a fragment of a fossil sponge, and recorded it as a fossil, or possibly described the fragment. This fact alone would have been valuable, but to make it bear its full fruit it was necessary to trace the fragment to its source, and then to spend time and labour in extracting from the stubborn rock the story it had to tell. Instances of this kind crowd on my memory as coming within my own ex- perience and observation. It is hopeful to think that the re- cord is daily becoming less imperfect ; it is stimulating to know that so much is only waiting for investigation. The his- tory never can be absolutely complete. Practically, to us it is infinite. Yet every series of facts known may be complete in itself for certain purposes, however many gaps there may be in the story. Even if we cannot find a continuous series be- tween the snails of the Coal formation or the sponges of the Quebec Group and their successors to-day, we can at least see that they are identical in plan and structure, and can note the differences of detail which fitted them for their places in the ancient or the modern world. Nor need we be too discontented if the order of succession, such as it is, does not exactly square with some theories we may have formed. Perhaps it may in the end lead us to greater and better truths. Another subject which merits attention here is the evidence which mere markings or other indications may sometimes give 50 IMPERFECTION OF THE GEOLOGICAL RECORD as to the existence of unknown creatures, and thus may be as important to us as the footprints of Friday to Robinson Crusoe. As I have been taking Canadian examples, I may borrow one here from Mr. Matthew, of St. John, New Brunswick. He remarks in one of his papers the manner in which the Trilobites of the early Cambrian are protected with defensive spines, and asks against what enemies they were intended to guard. That there were enemies is further proved by the oc- currence of Coprolites or masses of excrement, oval or cylin- drical in form, and containing fragments of shells of Trilobites, of Pteropods (Hyolithes) and of Lingula. There must there- fore have been marine animals of considerable size, which preyed on Trilobites. Dr. Hunt and myself have recorded similar facts from the Upper-Cambrian and Cambro- Silurian of the Province of Quebec. No remains, however, are known of animals which could have produced such coprolites, except, indeed, some of the larger worms of the period, and they seem scarcely large enough. In these circumstances Mr. Matthew falls back on certain curious marks or scratches with which large surfaces of these old rocks are covered, and which he names Ctenichnites or " Comb tracks." These markings seem to indicate the rapid motion of some animal touching the bottom with fins or other organs ; and as we know no fishes in these old rocks, the question recurs, What could it have been ? From the form and character of the markings Mr. Matthew infers (i) That these animals lived in "schools," or were social in their habits ; (2) That they had a rapid, direct, darting motion; (3) That they had three or four (at least) flexible arms ; (4) That these arms were furnished with hooks or spines ; (5) That the creatures swam with an easy motion, so that sometimes the arms of one side touched the bottom, sometimes those of the other. These indications point to animals allied to the modern squids or cuttlefishes, and as these animals may have had no hard parts capable of pre- IMPERFECTION OF THE GEOLOGICAL RECORD 51 servation, except their horny beaks, nothing might remain to indicate their presence except these marks on the bottom. Mr. Matthew therefore conjectures that there may have been large cuttlefishes in the Cambrian. Since, however, these are animals cf very high rank in their class, and are not certainly- known to us till a very much later period, their occurrence in these old rocks would be a very remarkable and unexpected fact. A discovery made by Walcott in the Western States since Mr. Matthew's paper was written, throws fresh light on the question. Remains of fishes have been found by the former in the Cambro Silurian rocks nearly as far back as Mr. Matthew's comb-tracks. Besides this, Pander in Russia has found in these old rocks curious teeth, which he refers conjecturally to fishes (Conodonts). Why may there not have been in the Cambrian large fishes having, like the modern sharks, cartilage or gristle instead of bone perhaps destitute of scale.*, and with small teeth which have not yet been de- tected. The fin rays of such fishes may have left the comb tracks, and in support of this I may say that there are in the Lower Carboniferous of Horton Bluff, in Nova Scotia, very similar tracks in beds holding many remains of fishes. Which- ever view we adopt we see good evidence that there were in the early Cambrian animals of higher grade than we have yet dreamt of. Observe, however, that if we could complete the record in this point it would only give us higher forms of life at an earlier time, and so push farther back their possible development from lower forms. I fear, indeed, that I can hold out little hopes to the evolutionists that a more complete geological record would help them in any way. It would possibly only render their position more difficult But the saddest of all the possible defects of the geological record is that it may want the beginning, and be like the Bible of some of the German historical critics, from which they 52 IMPERFECTION OF THE GEOLOGICAL RECORD eliminate as mythical everything before the time of the later Hebrew kings. Our attention is forcibly called to this by the condition of the fauna of the earliest Cambrian rocks. The discoveries in these in Wales, in Norway, and in America show us that the seas of this early period swarmed with animals re- presenting all the great types of invertebrate marine life. We have here highly organized Crustaceans, Worms, Mollusks and other creatures which show us that in that early age all these distinct forms of life were as well separated from each other as in later times, that eyes of different types, jointed limbs with nerves and muscles, and a vast variety of anatomical contrivances were as highly developed as at any subsequent time. 1 To a Darwinian evolutionist this means nothing less than that these creatures must have existed through countless ages of development from their imagined simple ancestral form or forms how long it is impossible to guess, since, unless change was more speedy in the infancy of the earth, the term of ages required must have far exceeded that from the Cam- brian to the Modern. Yet, to represent all this we have abso- lutely nothing except Eozoon in its solitary grandeur, and a 1 Walcott and Matthew record more than 160 species of 67 genera, in- cluding Sponges, Zoophytes, Echinoderms, Brachiopods, Bivalve and Univalve shellfishes, Trilobites and other Crustaceans from the Lower- Cambrian of the United States of America and Canada alone ; and these are but a portion of the inhabitants of the early Cambrian seas. There is a rich Scandinavian fauna of the same early date, and in England and Wales, Sailer, Hicks and Lapworth have described many fossils of the basal Cambrian. From year to year, also, discoveries of fossil remains are being made, both in America and Europe, in beds of older date than those previously known to be fossiliferous. At present, however, these remains are still few and imperfectly known, and it is not in all cases certain whether the beds in which they occur are pre-Cambrian or belong to the lowest members of that great system. It is unfortunate that so many of the strata between the Laurentian and the Cambrian seem to be of a character little likely to contain fossils ; being littoral deposits produced in times of much physical disturbance. Yet there must have been con- temporaneous beds of a different character, which may yet be discovered. IMPERFECTION OF THE GEOLOGICAL RECORD 53 few other forms, possibly of Protozoa and worms. An im- aginary phylogeny of animal life from Monads to Trilobites would be something as long as the whole geological history. Yet it would be almost wholly imaginary, for the record of the rocks tells little or nothing. In face of such an imperfection as this, geologists should surely be humble, 'and make confes- sion of ignorance to any extent that may be desired. Yet we may at least, with all humility and self-abasement, ask our critics how they know that this great blank really exists, and whether it may not be possible that the swarming life of the early Cambrian may, after all, have appeared suddenly on the stage in some way as yet unknown to us and to them. REFERENCES : " Fossil Sponges from the Quebec Group of Little Metis, Lower St. Lawrence": Transactions Royal Society of Canada, 1890. "Resume of the Carboniferous Land Shells of North America": American Journal of Science, 1880. "Burrows and Tracks of In- vertebrate Animals ": Journal Geological Society of London, 1890. "Notes on the Pleistocene of Canada" : Canadian Naturalist, 1876. " Air-breathers of the Coal Period " : Ibid., 1863. THE HISTORY OF THE NORTH ATLANTIC. DEDICATED TO THE MEMORY OF PROF. JOHN PHILLIPS, OF OXFORD, ONE OF THE MOST ABLE, EARNEST, AND GENIAL OF ENGLISH GEOLOGISTS ; AND OF OTHER EMINENT SCIENTIFIC MEN, NOW PASSED AWAY, WHO SUPPORTED HIM AS PRESIDENT OF THE BRITISH ASSOCIATION, AT ITS MEETING IN BIRMINGHAM, IN 1865. DISTRIBUTION OF LAND AND WATER CAUSES OF IRREGU- LARITIES OF THE SURFACE CRUST AND INTERIOR POSITION OF CONTINENTS PAST HISTORY OF THE ATLANTIC ITS RELATIONS TO LIFE ITS FUTURE 1- :' CHAPTER IV. THE HISTORY OF THE NORTH ATLANTIC. I HAD the pleasure of being present at the meeting of the British Association at Birmingham, in 1865 : a meeting attended by an unusually large number of eminent geologists, under the presidency of my friend Phillips. I had the further pleasure of being his successor at the meeting in the same place, in 1886; and the subject of this chapter is that to which I directed the attention of the Association in my Presidential address. I fear it is a feeble and imperfect utter- ance compared with that which might have been given forth by any of the great men present in 1865, and who have since left us, could they have spoken with the added knowledge of the intervening twenty years. The geological history of the Atlantic appeared to be a suitable subject for a trans-Atlantic president, and to a Society which had vindicated its claim to be British in the widest sense by holding a meeting in Canada, while it was also meditating a visit to Australia a visit not yet accomplished, but in which it may now meet with a worthy daughter in the Australian Association formed since the meeting of 1886. The subject is also one carrying our thoughts very far back in geological time, and connecting itself with some of the latest and most important discussions and discoveries in the science of the earth, furnishing, indeed, too many salient points to be profitably occupied in a single chapter. If we imagine an observer contemplating the earth from a 58 THE HISTORY OF THE NORTH ATLANTIC convenient distance in space, and scrutinizing its features as it rolls before him, we may suppose him to be struck with the fact that eleven-sixteenths of its surface are covered with water, and that the land is so unequally distributed that from one point of view he would see a hemisphere almost exclusively oceanic, while nearly the whole of the dry land is gathered in the opposite hemisphere. He might observe that large portions of the great oceanic areas of the Pacific and Antarctic Oceans are dotted with islands like a shallow pool with stones rising above its surface as if the general depth were small in com- parison with the area. Other portions of these oceans he might infer, from the colour of the water and the absence of islands, cover deep depressions in the earth's surface. He might also notice that a mass or belt of land surrounds each pole, and that the northern ring sends off to the southward three vast tongues of land and of mountain chains, terminating respectively in South America, South Africa, and Australia, towards which feebler and insular processes are given off by the antarctic continental mass. This, as some geographers have observed, l gives a rudely three-ribbed aspect to the earth, though two of the ribs are crowded together, and form the Eurasian mass or double continent, while the third is isolated in the single continent of America. He might also observe that the northern girdle is cut across, so that the Atlantic opens by a wide space into the Arctic Sea, while the Pacific is contracted toward the north, but confluent with the Antarctic Ocean. The Atlantic is also relatively deeper and less cum- bered with islands than the Pacific, which has the highest ridges near its shores, constituting what some visitors to the Pacific coast of America have not inaptly called the " back of the world," while the wider slopes face the narrower ocean. The Pacific and Atlantic, though both depressions or flat- 1 Dana, " Manual of Geology," introductory part. Green, " Vestiges of a Molten Globe," has summed up these facts. THE HISTORY OF THE NORTH ATLANTIC 59 tenings of the earth, are, as we shall find, different in age, character, and conditions; and the Atlantic, though the smaller, is the older, and, from the geological point of view, in some respects, the more important of the two ; while, by virtue of its lower borders and gentler slope, it is, though the smaller basin, the recipient of the greater rivers, and of a proportionately great amount of the drainage of the land. 1 If our imaginary observer had the means of knowing any- thing of the rock formations of the continents, he would notice that those bounding the North Atlantic are, in general, of great age some belonging to the Laurentian system. On the other hand, he would see that many of the mountain ranges along the Pacific are comparatively new, and that modern igneous action occurs in connection with them. Thus he might see in the Atlantic, though comparatively narrow, a more ancient feature of the earth's surface ; while the Pacific belongs to more modern times. But he would note, in con- nection with this, that the oldest rocks of the great continental masses are mostly toward their northern ends ; and that the borders of the northern ring of land, and certain ridges en- tending southward from it, constitute the most ancient and permanent elevations of the earth's crust, though now greatly surpassed by mountains of more recent age nearer the equator, so that the continents of the northern hemisphere seem to have grown progressively from north to south. If the attention of our observer were directed to more modern processes, he might notice that while the antarctic continent freely discharges its burden of ice to the ocean north of it, the arctic ice has fewer outlets, and that it mainly dis- charges itself through the North Atlantic, where also the great mass of Greenland stands as a huge condenser and cooler, 1 Mr. Mellard Reade, in two Presidential addresses before the Geo- logical Society of Liverpool, has illustrated this point and its geological consequences. S.E;. 5 60 THE HISTORY OF THE NORTH ATLANTIC unexampled elsewhere in the world, throwing every spring an immense quantity of ice into the North Atlantic, and more especially into its western part. On the other hand, he might learn from the driftage of weed and the colour of the water, that the present great continuous extension and form of the American continent tend to throw northward a powerful branch of the equatorial current, which, revolving around the North Atlantic, counteracts the great flow of ice which otherwise would condemn it to a perpetual winter. Further, such an observer would not fail to notice that the ridges which lie along the edges of the oceans and the ebul- litions of igneous matter which proceed, or have proceeded from them, are consequences of the settling downward of the great oceanic depressions, a settling ever intensified by their receiving more and more of deposit on their surfaces ; and that this squeezing upward of the borders of these depressions into folds has been followed or alternated with elevations and depressions without any such folding, and proceeding from other causes. On the whole, it would be apparent that these actions are more vigorous now at the margins of the Pacific area, while the Atlantic is backed by very old foldings, or by plains and slopes from which it has, so to speak, dried away without any internal movement. Thus it would appear that the Pacific is the great centre of earth-movement, while the Atlantic trench is the more potent regulator of temperature, and the ocean most likely to be severely affected in this respect by small changes of its neighbouring land. Last of all, an observer, such as I have supposed, would see that the oceans are the producers of moisture and the conveyors of heat to the northern regions of the world, and that in this respect and in the immense condensation and delivery of ice at its north end, the Atlantic is by far the more active, though the smaller of the two. So much could be learned by an extra-mundane observer ; THE HISTORY OF THE NORTH ATLANTIC 6 1 but unless he had also enjoyed opportunities of studying the rocks of the earth in detail and close at hand, or had been favoured by some mundane friend with a perusal of " Lyell's Elements," or "Dana's Manual," he would not be able to ap- preciate as we can the changes which the Atlantic has seen in geological time, and in which it has been a main factor. Nor could he learn from such superficial observation certain secrets of the deep sea, which have been unveiled by the sounding lead, the inequalities of the ocean basin, its few profound depths, like inverted mountains or table-lands, its vast nearly flat abyssmal floor, and the sudden rise of this to the hundred fathom line, forming a terrace or shelf around the sides of the continents. These features, roughly represented in the map prefixed, he would be unable to perceive. Before leaving this broad survey, we may make one further remark. An observer, looking at the earth from without, would notice that the margins of the Atlantic and the main lines of direction of its mountain chains are north-east and south-west, and north-west and south-east, as if some early causes had determined the occurrence of elevations along great circles of the earth's surface tangent to the polar circles. We are invited by the preceding general glance at the surface of the earth to ask certain questions respecting the Atlantic, (i) What has at first determined its position and form? (2) What changes has it experienced in the lapse of geological time ? (3) What relations have these changes borne to the development of life on the land and in the water ? (4) W T hat is its probable future ? Before attempting to answer these questions, which I shall not take up formally in succession, but rather in connection with each other, it is necessary to state, as briefly as possible, certain general conclusions respecting the interior of the earth. It is popularly supposed that we know nothing of this beyond a superficial crust perhaps averaging 50,000 to 100,000 feet in 62 THE HISTORY OF THE NORTH ATLANTIC thickness. It is true we have no means of exploration in the earth's interior, but the conjoined labours of physicists have now proceeded sufficiently far to throw much inferential light on the subject, and to enable us to make some general affirma- tions with certainty ; and these it is the more necessary to state distinctly, since they are often treated as mere subjects of speculation and fruitless discussion. (1) Since the dawn of geological science, it has been evi- dent that the crust on which we live must be supported on a plastic or partially liquid mass of heated rock, approximately uniform in quality under the whole of its area. This is a legitimate conclusion from the wide distribution of volcanic phenomena, and from the fact that the ejections of volcanoes, while locally of various kinds, are similar in every part of the world. It led to the old idea of a fluid interior of the earth, but this seems now generally abandoned, and this interior heated and plastic layer is regarded as merely an under-crust, resting on a solid nucleus. 1 (2) We have reason to believe, as the result of astronomical investigations, 2 that, notwithstanding the plasticity or liquidity of the under-crust, the mass of the earth its nucleus as we may call it is practically solid and of great density and hardness. Thus we have the apparent paradox of a solid yet fluid earth ; solid in its astronomical relations, liquid or 1 I do not propose to express any definite opinion as to this question, as either conclusion will satisfy the demands of geology. It would seem, however, that astronomers now admit a slight periodical deformation of the crust. See Lord Kelvin's Anniversary Address to Royal Society, 1892. 2 Hopkins, Mallet, Lord Kelvin, and Prof. G. H. Darwin maintain the solidity and rigidity of the earth on astronomical grounds ; but different conclusions have been reached by Fisher, Hennesey, Delaunay, and Airy. In America, Hunt, Barnard and Crosby, Button, Le Conte and Wadsworth have discussed these questions. Bonney has suggested that a mass may be slowly mobile under long-continued pressure, while rigid with reference to more sudden movements. THE HISTORY OF THE NORTH ATLANTIC 63 plastic for the purposes of volcanic action and superficial move- ments. (3) The plastic sub-crust is not in a state of dry igneous fusion, but in that condition of aqueo-igneous or hydrothermic fusion which arises from the action of heat on moist substances, and which may either be regarded as a fusion or as a species of solution at a very high temperature. This we learn from the phenomena of volcanic action, and from the composition of the volcanic and plutonic rocks, as well as from such chemical experiments as those of Daubrtfe, and of Tilden, and Shenstone. 1 It follows that water or steam, as well as rocky matter, may be ejected from the under-crust. (4) The interior sub-crust is not perfectly homogeneous, but may be roughly divided into two layers or magmas, as they have been called ; an upper, highly silicious or acidic, of low specific gravity and light-coloured, and corresponding to such kinds of plutonic and volcanic rocks as granite and trachyte ; and a lower, less silicious or more basic, more dense, and more highly charged with iron, and corresponding to such igneous rocks as the dolerites, basalts, and kindred lavas. It is interesting here to note that this conclusion, elaborated by Durocher and Von Waltershausen, and usually connected with their names, appears to have been first announced by John Phillips, in his " Geological Manual," and as a mere common- sense deduction from the observed phenomena of volcanic action and the probable results of the gradual cooling of the earth. It receives striking confirmation from the observed succession of acidic and basic volcanic rocks of all geological periods and in all localities. It would even seem, from recent spectroscopic investigations of Lockyer, that there is evidence of a similar succession of magmas in the heavenly bodies, and the discovery by Nordenskiold of native iron in Greenland 1 Phil. 7rans., 1884. Also Crosby in Prof. Boston Soc. Nat. Hist., 1883. 64 THE HISTORY OF THE NORTH ATLANTIC basalts, affords a probability that the inner magma is in part metallic, and possibly, that vast masses of unoxidised metals exist in the central portion of the earth. (5) Where rents or fissures form in the upper crust, the material of the lower crust is forced upward by the pressure of the less supported portions of the former, giving rise to volcanic phenomena either of an explosive or quiet character, as may be determined by contact with water. The underlying material may also be carried to the surface by the agency of heated water, producing those quiet discharges which Hunt has named crenitic. It is to be observed here that explosive volcanic phenomena, and the formation of cones, are, as Prestwich has well remarked, characteristic of an old and thickened crust; quiet ejection from fissures and hydro- thermal action may have been more common in earlier periods and with a thinner over-crust. This is an important con- sideration with reference to those earlier ages referred to in chapter second. (6) The contraction of the earth's interior by cooling and by the emission of material from below the over-crust, has caused this crust to press downward, and therefore laterally, and so to effect great bends, folds, and plications ; and these, modified subsequently by surface denudation, and the piling of sediments on portions of the crust, constitute mountain chains and continental plateaus. As Hall long ago pointed out, 1 such lines of folding have been produced more especially where thick sediments had been laid down on the sea-bottom, and where, in consequence, internal expansion of the crust had occurred from heating below. Thus we have here another apparent paradox, namely, that the elevations of the earth's crust occur in the places where the greatest burden of de- 1 Hall (American Association Address, 1857, subsequently republished, with additions, as "Contributions to the Geological History of the American Continent"), Mallet, Rogers, Dana, La Conte, etc. THE HISTORY OF THE NORTH ATLANTIC 65 trims has been laid down upon it, and where, consequently, the crust has been softened and depressed. We must beware, in this connection, of exaggerated notions of the extent of con- traction and of crumpling required to form mountains. Bonney has well shown, in lectures delivered at the London Institu- tion, that an amount of contraction, almost inappreciable in comparison with the diameter of the earth, would be sufficient ; and that, as the greatest mountain chains are less than -^^th. of the earth's radius in height, they would, on an artificial globe a foot in diameter, be no more important than the slight inequalities that might result from the paper gores overlapping each other at the edges. This thinness of the crushed crust agrees with the deductions of physical science as to the shallowness of the superficial layer of compression in a cooling globe. It is perhaps not more than five miles in thickness. A singular proof of this is seen by the extension of straight cracks filled with volcanic rock in the Laurentian districts of Canada. 1 The beds of gneiss and associated rocks are folded and crumpled in a most complex manner, yet they are crossed by these faults, as a crack in a board may tear a sheet of paper or a thin veneer glued on it. We thus see that the crumpled Laurentian crust was very thin, while the uncrushed sub-crust determined the line of fracture. (7) The crushing and sliding of the over-crust implied in these movements raise some serious questions of a physical character. One of these relates to the rapidity or slowness of such movements, and the consequent degree of intensity of the heat developed, as a possible cause of metamorphism of rocks. Another has reference to the possibility of changes in the equilibrium of the earth itself, as resulting from local collapse and ridging. These questions in connection with the 1 As, for instance, the great dyke running nearly in a straight line from near St. Jerome along the Ottawa to Templeton, on the Ottawa, and be- yond, a distance of more than a hundred miles. 66 THE HISTORY OF THE NORTH ATLANTIC present dissociation of the axis of rotation from the magnetic poles, and with changes of climate, have attracted some atten- tion, 1 and probably deserve further consideration on the part of physicists. In so far as geological evidence is concerned, it would seem that the general association of crumpling with metamorphism indicates a certain rapidity in the process of mountain-making, and consequent development of heat ; and the arrangement of the older rocks around the Arctic basin for- bids us from assuming any extensive movement of the axis of rotation, though it does not exclude changes to a limited extent. (8) It appears from the above that mountains and conti- nental elevations may be of three kinds, (a) They may con- sist of material thrown out of volcanic rents, like earth out of a mole burrow. Mountains like Vesuvius and JEtna are of this kind. () They may be parts of wide ridges or chains variously cut and modified by rains and rivers. The Lebanon and the Catskill Mountains are cases in point, (c) They may be lines of crumpling by lateral pressure. The greatest moun- tains, like the Cordillera, the Alps, and the Appalachians are of this kind, and such mountains may represent lateral pressure occurring at various times, and whose results have been greatly modified subsequently. I wish to formulate these principles as distinctly as possible, and as the result of all the long series of observations, calcu- lations, and discussions since the time of Werner and Hutton, and in which a vast number of able physicists and naturalists have borne a part, because they may be considered as certain deductions from our actual knowledge, and because they lie at the foundation of a rational physical geology. We may roughly popularise these deductions by comparing the earth to a drupe or stone-fruit, such as a plum or peach 1 See recent papers of Oldham and Fisher, in Geological Magazine, and Philosophical Magazine, July, 1886. Also Peroche, " Revol. Polahes." Paris, 1886. THE HISTORY OF THE NORTH ATLANTIC 6/ somewhat dried up. It has a large and intensely hard stone and kernel, a thin pulp made up of two layers, an inner, more dense and dark-coloured, and an outer, less dense and lighter- coloured. These constitute the under-crust. On the outside it has a thin membrane or over-crust. In the process of drying it has slightly shrunk, so as to produce ridges and hollows of the outer crust, and this outer crust has cracked in some places, allowing portions of the pulp to ooze out an some of them its lower dark substance, in others, its upper and lighter material. The analogy extends no farther, for there is nothing in our withered fruit to represent the oceans occupying the lower parts of the surface, or the deposits which they have laid down. Here a most important feature demands attention. The rain, the streams, and the sea are constantly cutting down the land and depositing it in the bed of the waters. Thus weight is taken from the land, and added to the sea bed. Geological facts, such as the great thickness of the coal measures, in which we find thousands of feet of sediment, all of which must have been deposited in shallow water, and the accumulation of hundreds of feet of superficial material in deltas at the mouth of great rivers, show that the crust of the earth is so mobile as to yield downward to every pressure, however slight. 1 It may do this slowly and gradually, or by jumps from time to time ; and this yielding necessarily tends to squeeze up the edges of the depressed portions into ridges, and to cause lateral move- ment and ejection of volcanic matter at intervals. Keeping in view these general conclusions, let us now turn to their bearing on the origin and history of the North Atlantic. Though the Atlantic is a deep ocean, its basin does not constitute so much a depression of the crust of the earth as a flattening of it, and this, as recent soundings have shown, with a slight ridge or elevation along its middle, and banks or terraces fringing the edges, so that its form is not so much 1 Starkie Gardiner, Nature, December, 1889. 68 THE HISTORY OF THE NORTH ATLANTIC that of a basin as that of a shallow elongated plate with its middle a little raised. Its true margins are composed of portions of the over-crust folded, overlapped and crushed, as if by lateral pressure emanating from the sea itself. We can- not, for example, look at a geological map of America without perceiving that the Appalachian ridges, which intervene be- ween the Atlantic and the St. Lawrence valley, have been driven bodily back by a force acting from the east, and that they have resisted this pressure only where, as in the Gulf of St. Lawrence and the Catskill region of New York, they have been protected by outlying masses of very old rocks, as, for example, by that of the island of Newfoundland and that of the Adirondack Mountains. The admirable work begun by my friend and fellow-student, Professor James Nicol, followed up by Professor Lapworth, and now, after long controversy, fully confirmed by the recent observations of the Geological Survey of Scotland, has shown the most intense action of the same kind on the east side of the ocean in the Scottish high- lands ; and the more widely distributed Eozoic and other old rocks of Scandinavia may be appealed to in further evidence of this. 1 If we now inquire as to the cause of the Atlantic depres- sion, we must go back to the time when the areas occupied by the Atlantic and its bounding coasts were parts of the shoreless sea in which the earliest gneisses or stratified granites of the Laurentian age were being laid down in vastly extended beds. These ancient crystalline rocks have been the subject of much discussion and controversy, to which reference has been made in a previous chapter. It will be observed, in regard to these theories, that they do 1 Address to Geological Section, Brit. Assoc., by Prof. Judd, Aberdeen Meeting, 1885. According to Rogers, the crumpling of the Appalachians has reduced a breadth of 158 miles to about 60. Geikie, Address, Geo- logical Society, 1891-2. THE HISTORY OF THE NORTH ATLANTIC 69 not suppose that the old gneiss is an ordinary sediment, but that all regard it as formed in exceptional circumstances, these circumstances being the absence of land and of subaerial decay of rock, and the presence wholly or principally of the material of the upper surface of the recently hardened crust. This being granted, the question arises, Ought we not to com- bine the several theories as to the origin of gneiss, and to believe that the cooling crust has hardened in successive layers from without inward; that at the same time fissures were locally discharging igneous matter to the surface ; that matter held in supension in the ocean and matter held in solution by heated waters rising from beneath the outer crust were ming- ling their materials in the deposits of the primitive ocean ? 1 It would seem that the combination of all these agencies may safely be evoked as causes of the pre-Atlantic deposits. This is the eclectic position I have maintained in a previous chap- ter, and which I hold to be in every way the most probable. Let us suppose, then, the floor of old ocean covered with a flat pavement of gneiss, or of that material which is now gneiss, the next question is, How and when did this original bed become converted into sea and land ? Here we have some things certain, others most debateable. That the cooling mass, especially if it was sending out volumes of softened rocky material, either in the form of volcanic ejections or in that of matter dissolved in heated water, and piling this on the surface, must soon become too small for its shell, is apparent ; but when and where would the collapse, crushing and wrink- ling inevitable from this cause begin? The date is indi- cated by the lines of old mountain chains which traverse the Laurentian districts; but the reason why is less apparent. The more or less unequal cooling, hardening and conductive power of the outer crust we may readily assume. The drifthge unequally of water-borne detritus to the south-west by the 1 Hunt, Transactions Royal Society of Canada, 1885. 70 THE HISTORY OF THE NORTH ATLANTIC bottom currents of the sea is another cause, and, as we shall soon see, most effective. Still another is the greater cooling and hardening of the crust in the polar regions, and the ten- dency to collapse of the equatorial protuberance from the slackening of the earth's rotation. Besides these, the internal tides of the earth's substance at the times of solstice would exert an oblique pulling force on the crust, which might tend to crack it along diagonal lines. From whichever of these causes, or the combination of the whole, we know that, within the Laurentian time, folded portions of the earth's crust began to rise above the general surface, in broad belts running from north-east to south-west, and from north-west to south-east, where the older mountains of Eastern America and Western Europe now stand, and that the subsidence of the oceanic areas, allowed by this crumpling of the crust, permitted other areas on both sides of the Atlantic to form limited table-lands. This was the commencement of a process repeated again and again in subsequent times, and which began in the middle Laurentian, when for the first time we find beds of quartzite, limestone, and iron ore, and graphite beds, indicating that there was already land and water, and that the sea, and perhaps the land, swarmed with forms of animal and plant life, unknown, for the most part, now. Independently of the questions as to the animal nature of Eozoon, I hold that we know, as certainly as we can know anything inferentially, the existence of these primitive forms of life. If I were to conjecture what were these early forms of plant and animal life, still unknown to us by actual specimens, I would suppose that, just as in the Palaeo- zoic, the acrogens culminated in gigantic and complex forest trees, so in the Laurentian, the algae, the lichens, and the mosses grew to dimensions and assumed complexity of struc- ture unexampled in later times, and that, in the sea, the humbler forms of Protozoa and Sea Mosses were the dominant types, but in gigantic and complex forms. The land of this THE HISTORY OF THE NORTH ATLANTIC 7 1 period was probably limited, for the most part, to high lati- tudes, and its aspect, though more rugged and abrupt, and of greater elevation, must have been of that character which we still see in the Laurentian hills. The distribution of this ancient land is indicated by the long lines 01 old Laurentian rock extending from the Labrador coast and the north shore of the St. Lawrence, and along the eastern slopes of the Appalachians in America, and the like rocks of the Hebrides, the Western Highlands, and the Scandinavian mountains. A small but interesting remnant is that in the Malvern Hills, so well described by Holl. It will be well to note here, and to fix on our minds, that these ancient ridges of Eastern America and Western Europe have been greatly denuded and wasted since Laurentian times, and that it is along their eastern sides that the greatest sedimentary accumulations have been de- posited. From this time dates the introduction of that dominance of existing causes which forms the basis of uniformitarianism in geology, and which had to go on with various and great modi- fications of detail, through the successive stages of the geolo- gical history, till the land and water of the northern hemisphere attained to their present complex structure. So soon as we have a circumpolar belt or patches of Eozoic l land and ridges running southward from it, we enter on new and more complicated methods of growth of the continents and seas. Portions of the oldest crystalline rocks, raised out of the protecting water, were now eroded by atmospheric agents, and especially by the carbonic acid, then existing in the atmosphere perhaps more abundantly than at present, under whose influence the hardest of the gneissic rocks gradually decay. The arctic lands were subjected, in addition, to the powerful mechanical force of frost and thaw. Thus every shower of rain and every swollen stream would carry into the 1 Or Archaean, or pre-Cambrian, if these terms are preferred. 72 THE HISTORY OF THE NORTH ATLANTIC sea the products of the waste of land, sorting them into fine clays and coarser sands ; and the cold currents which cling to the ocean bottom, now determined in their courses, not merely by the earth's rotation, but also by the lines of folding on both sides of the Atlantic, would carry south-westward, and pile up in marginal banks of great thickness the debris produced from the rapid waste of the land already existing in the Arctic regions. The Atlantic, opening widely to the north, and having large rivers pouring into it, was, especially, the ocean characterised, as time advanced, by the prevalence of these phenomena. Thus, throughout the geological history it has happened that, while the middle of the Atlantic has received merely organic deposits of shells of foraminifera and similar organisms, and this probably only to a small amount, its margins have had piled upon them beds of detritus of im- mense thickness. Professor Hall, of Albany, was the first geologist who pointed out the vast cosmic importance of these deposits, and that the mountains of both sides of the Atlantic owe their origin to these great lines of deposition, along with the fact, afterwards more fully insisted on by Rogers, that the portijns of the crust which received these masses of debris became thereby weighted down and softened, and were more liable than other parts to lateral crushing. Thus, in the later Eozoic and early Palaeozoic times, which succeeded the first foldings of the oldest Laurentian, great ridges were thrown up, along the edges of which were beds of limestone, and on their summits and sides, thick masses of ejected igneous rocks. In the bed of the central Atlantic there are no such accumulations. It must have been a flat, or slightly ridged, plate of the ancient gneiss, hard and resisting, though perhaps with a few cracks, through which igneous mat- ter welled up, as in Iceland and the Azores in more modern times. In this condition of things we have causes tending to perpetuate and extend the distinctions of ocean and continent, THE HISTORY OF THE NORTH ATLANTIC 73 mountain and plain, already begun ; and of these we may more especially note the continued subsidence of the areas of greatest marine deposition. This has long attracted attention, and affords very convincing evidence of the connection of sedi- mentary deposit as a cause with the subsidence of the crust. 1 We are indebted to a French physicist, M. Faye, for an impor- tant suggestion on this subject. It is that the sediment accu- mulated along the shores of the ocean presented an obstacle to radiation, and consequently to cooling of the crust, while the ocean floor, unprotected and unweighted, and constantly bathed with currents of cold water having great power of con- vection of heat, would be more rapidly cooled, and so would become thicker and stronger. This suggestion is complemen- tary to the theory of Professor Hall, that the areas of greatest deposit on the margins of the ocean are necessarily those of greatest folding and consequent elevation. We have thus a hard, thick, resisting ocean bottom, which, as it settles down to- ward the interior, under the influence of gravity, squeezes upwards and folds and plicates all the soft sediments deposited on its edges. The Atlantic area is almost an unbroken cake of this kind. The Pacific area has cracked in many places, allowing the interior fluid matter to exude in volcanic ejec- tions. It may be said that all this supposes a permanent continu- ance of the ocean basins, whereas many geologists postulate a mid-Atlantic continent to give the thick masses of detritus found in the older formations both in Eastern America and Western Europe, and which thin off in proceeding into the 1 Button in Report oj U.S. Geological Survey t 1891. From facts stated in this report and in my "Acadian Geology," it is apparent that in the Western States and in the coalfields of Novia Scotia, shallow-water deposits have been laid down, up to thicknesses of 10,000 to 20,000 feet in connection with continuous subsidence. See also a paper by Ricketts in the Geol. Mag., 1883. 74 THE HISTORY OF THE NORTH ATLANTIC interior of both continents. I prefer, as already stated, to consider these belts of sediment as the deposits of north- ern currents, and derived from arctic land, and that, like the great banks off the American coast at the present day, which are being built up by the present arctic current, they had little to do with any direct drainage from the adjacent shore. We need not deny, however, that such ridges of land as existed along the Atlantic margins were contributing their quota of river-borne material, just as on a still greater scale the Amazon and Mississippi are doing now, and this especially on the sides toward the present continental plateaus, though the greater part must have been derived from the wide tracts of Lauren- tian land within the Arctic Circle, or near to it. It is further obvious that the ordinary reasoning respecting the necessity of continental areas in the present ocean basins would actually oblige us to suppose that the whole of the oceans and conti- nents had repeatedly changed places. This consideration op- poses enormous physical difficulties to any theory of alterna- tions of the oceanic and continental areas, except locally at their margins. But the permanence of the Atlantic depression does not ex- clude the idea of successive submergences of the continental plateaus and marginal slopes, alternating with periods of eleva- tion, when the ocean retreated from the continents and con- tracted its limits. In this respect the Atlantic of to-day is much smaller than it was in those times when it spread widely over the continental plains and slopes, and much larger than it has been in times of continental elevation. This leads us to the further consideration that, while the ocean beds have been sinking, other areas have been better supported, and constitute the continental plateaus ; and that it has been at or near the junctions of these sinking and rising areas that the thickest de- posits of detritus, the most extensive foldings, and the greatest ejections of volcanic matter have occurred. There has thus THE HISTORY OF THE NORTH ATLANTIC 75 been a permanence of the position of the continents and oceans throughout geological time, but with many oscillations of these areas, producing submergences and emergences of the land. In this way we can reconcile the vast vicissitudes of the conti- nental areas in different geological periods with that continuity of development from north to south, and from the interiors to the margins, which is so marked a feature. We have, for this reason, to formulate another apparent geological paradox, namely, that while, in one sense, the continental and oceanic areas are permanent, in another, they have been in continual movement. Nor does this view exclude extension of the con- tinental borders or of chains of islands beyond their present limits, at certain periods ; and indeed, the general principle already stated, that subsidence of the ocean bed has produced elevation of the land, implies in earlier periods a shallower ocean and many possibilities as to volcanic islands, and low continental margins creeping out into the sea ; while it is also to be noted that there are, as already stated, bordering shelves, constituting shallows in the ocean, which at certain periods have emerged as land. We are thus compelled, as already stated, to believe in the contemporaneous existence in all geological periods, except perhaps the earliest of them, of the three distinct conditions of areas on the surface of the earth, defined in chapter second oceanic areas of deep sea, continental plateaus and marginal shelves, and lines of plication and folding. In the successive geological periods the continental pla- teaus, when submerged, owing to their vast extent of warm and shallow sea, have been the great theatres of the development of marine life and of trie deposition of organic limestones, and when elevated, they have furnished the abodes of the noblest land faunas and floras. The mountain belts, especially in the north, have been the refuge and stronghold of land life in periods of submergence ; and the deep ocean basins have s. E. 6 76 THE HISTORY OF THE NORTH ATLANTIC been the perennial abodes of pelagic and abyssal creatures and the refuge of multitudes of other marine animals and plants in times of continental elevation. These general facts are full of importance with reference to the question of the succession of formations and of life in the geological history of the earth. So much space has been occupied with these general views, that it would be impossible to trace the history of the Atlantic in detail through the ages of the Palaeozoic, Mesozoic, and Tertiary. We may, however, shortly glance at the changes of the three kinds of surface already referred to. The bed of the ocean seems to have remained, on the whole, abyssal ; but there were probably periods when those shallow reaches of the Atlantic which stretch across its most northern portion, and partly separate it from the Arctic basin, presented connecting coasts or continuous chains of islands sufficient to permit animals and plants to pass over. 1 At certain periods also there were, not unlikely, groups of volcanic islands, like the Azores, in the temperate or tropical Atlantic. More especially might this be the case in that early time when it was more like the present Pacific ; and the line of the great volcanic belt of the Mediterranean, the mid-Atlantic banks, the Azores and the West India Islands point to the possibility of such partial con- nections. These were stepping stones, so to speak, over which land organisms might cross, and some of these may be con- nected with the fabulous or pre-historic Atlantis. In the Palaeozoic period, the distinctions already referred to. into continental plateaus, mountain ridges, and ocean depths, were first developed, and we find, already, great masses of sedi- ment accumulating on the seaward sides of the old Laurentian ridges, and internal deposits thinning away from these ridges over the submerged continental areas, and presenting dissimilar 1 It would seem, from Geikie's description of the Faroe Islands, that they may be a remnant of such connecting land, dating from the Cretaceous or Eocene period. THE HISTORY OF THE NORTH ATLANTIC 7/ conditions of sedimentation. It would seem also that, as Hicks has argued for Europe, and Logan and Hall for America, this Cambrian age was one of slow subsidence of the land previously elevated, accompanied with or caused by thick deposits of detritus along the borders of the subsiding shore, which was probably covered with the decomposing rock arising from long ages of subaerial waste. In the coal formation age its characteristic swampy flats stretched in some places far into the shallower parts of the ocean. 1 In the Permian, the great plicated mountain margins were fully developed on both sides of the Atlantic. In the Jurassic, the American continent probably extended farther to the sea than at present. In the Wealden age there was much land to the west and north of Great Britain, and Professor Bonney has directed attention to the evidence of the existence of this land as far back as the Trias, while Mr. Starkie Gardiner has insisted on connecting links to the southward, as evidenced by fossil plants. So late as the Post-glacial, or early human period, large tracts, now submerged, formed portions of the continents. On the other hand, the interior plains of America and Europe were often submerged. Such submergences are indicated by the great limestones of the Palaeozoic, by the chalk and its representative beds in the Cretaceous, by the Num- mulitic formation in the Eocene, and lastly, by the great Pleis- tocene submergence, one of the most remarkable of all, one in which nearly the whole northern hemisphere participated, and which was probably separated from the present time by only a few thousands of years. 2 These submergences and ele- 1 I have shown the evidence of this in the remnants of Carboniferous districts once more extensive on the Atlantic coast of Nova Scotia and Cape Breton ("Acadian Geology"). 2 The recent surveys of the Falls of Niagara coincide with a great many evidences to which I have elsewhere referred in proving that the Pleistocene submergence of America and Europe came to an end not more than ten 78 THE HISTORY OF THE NORTH ATLANTIC vations were not always alike on the two sides of the Atlantic. The Salina period of the Silurian, for example, and the Jurassic, show continental elevation in America not shared by Europe. The great subsidences of the Cretaceous and the Eocene were proportionally deeper and wider on the eastern continent, and this and the direction of the land being from north to south, cause more ancient forms of life to survive in America. These elevations and submergences of the plateaus alternated with the periods of mountain-making plication, which was going on at intervals, at the close of the Eozoic, at the beginning of the Cambrian, at the close of the Siluro-Cambrian, in the Permian, and in Europe and Western America in the Tertiary. The series of changes, however, affecting all these areas was of a highly complex character in detail. 1 We may also note a fact which I have long ago insisted on, 1 the regular pulsation of the continental areas, giving us alter- nations in each great system of deep-sea and shallow-water beds, so that the successive groups of formations may be di- vided into triplets of shallow- water, deep-water, and shallow- water strata, alternating in each period. This law of succession applies more particularly to the formations of the continental plateaus, rather than to those of the ocean margins, and it shows that, intervening between the great movements of plica- tion there were subsidences of those plateaus, or elevations of the sea bottom, which allowed the waters to spread themselves over all the inland spaces between the great folded mountain ranges of the Atlantic borders. In referring to the ocean basins we should bear in mind that there are three of these in the northern hemisphere the Arctic, the Pacific, and the Atlantic. De Ranee has ably thousand years ago, and was itself not of very great duration. Thus in Pleistocene times the land must have been submerged and re-elevated in a very rapid manner. 1 " Acadian Geology." THE HISTORY OF THE NORTH ATLANTIC 79 summed up the known facts as to Arctic geology in a series of articles in Nature, from which it appears that this area pre- sents from without inwards a succession of older and newer formations from the Eozoic to the Tertiary, and that its extent must have been greater in former periods than at present, while it must have enjoyed a comparatively warm climate from the Cambrian to the Pleistocene period. The relations of its deposits and fossils are closer with those of the Atlantic than with those of the Pacific, as might be anticipated from its wider opening into the former. Blandford has recently remarked on the correspondence of the marginal deposits around the Pacific and Indian oceans, 1 and Dr. Dawson informs me that this is equally marked in comparison with the west coast of America, but these marginal areas have not yet gained much on the ocean. In the North Atlantic, on the other hand, there is a wide belt of comparatively modern rocks on both sides, more especially toward the south and on the American side ; but while there appears to be a perfect correspondence on both sides of the Atlantic, and around the Pacific respectively, there seems to be less parallelism between the deposits and forms of life of the two oceans, as compared with each other, and less correspondence in forms of life, especially in modern times. Still, in the earlier geological ages, as might have been antici- pated from the imperfect development of the continents, the same forms of life characterise the whole ocean from Australia to Arctic America, and indicate a grand unity of Pacific and 1 Journal of Geological Society, May, 1886. Blandford's statements re- specting the mechanical deposits of the close of the Palaeozoic in the Indian Ocean, whether these are glacial or not, would seem to show a correspond- ence with the Permian conglomerates and earth movements of the Allan- tic area ; but since that time the Atlantic has enjoyed comparative repose. The Pacific seems to have reproduced the conditions of the Carboniferous in the Cretaceous age, and seems to have been less affected by the great changes of the Pleistocene. 80 THE HISTORY OF THE NORTH ATLANTIC Atlantic life not equalled in later times, 1 and which speaks of true contemporaneity rather than of what has been termed homotaxis or mere likeness of orders. We may pause here for a moment to notice some of the effects of Atlantic growth on modern geography. It has given us rugged and broken shores, composed of old rocks in the north, and newer formations and softer features to- ward the south. It has given us marginal mountain ridges and internal plateaus on both sides of the sea. It has pro- duced certain curious and by no means accidental corre- spondences of the eastern and western sides. Thus the solid basis on which the British Islands stand may be compared with Newfoundland and Labrador, the English Channel with the Gulf of St. Lawrence, the Bay of Biscay with the Bay of Maine, Spain with the projection of the American land at Cape Hatteras, the Mediterranean with the Gulf of Mexico. The special conditions of deposition and plication necessary to these results, and their bearing on the character and pro- ductions of the Atlantic basin, would require a volume for their detailed elucidation. Thus far our discussion has been limited almost entirely to physical causes and effects. If we now turn to the life history of the Atlantic, we are met at the threshold with the question of climate, not as a thing fixed and immutable, but as changing from age to age in harmony with geographical mutations, and producing long cosmic summers and winters of alternate warmth and refrigeration. We can scarcely doubt that the close connection of the Atlantic and Arctic oceans is one factor in those remarkable vicissitudes of climate experienced by the former, and in which the Pacific area has also shared in connection with the 1 Daintree and Etheridge, " Queensland Geology, "Journal Geological Society, August, 1872 ; R. Elheridge, Junior, "Australian Fossils," Trans. Phys. Soc., Edin., 1880. THE HISTORY OF THE NORTH ATLANTIC 8 1 Antarctic Sea. No geological facts are indeed at first sight more strange and inexplicable than the changes of climate in the Atlantic area, even in comparatively modern periods. We know that in the early Tertiary temperate conditions reigned as far north as the middle of Greenland, and that in the Pleisto- cene the Arctic cold advanced until an almost perennial winter prevailed half way to the equator. It is no wonder that nearly every cause available in the heavens and the earth has been invoked to account for these astounding facts. I shall, I trust, be excused if, neglecting most of these theoretical views, I venture to invite attention, in connection with this question, chiefly to the old Lyellian doctrine of the modification of climate by geographical changes. Let us, at least, consider how much these are able to account for. The ocean is a great equalizer of extremes of temperature. It does this by its great capacity for heat, and by its cooling and heating power when passing from the solid into the liquid and gaseous states, and the reverse. It also acts by its mobility, its currents serving to convey heat to great distances, or to cool the air by the movement of cold icy waters. The land, on the other hand, cools or warms rapidly, and can transmit its influence to a distance only by the winds, and the influence so transmitted is rather in the nature of a disturbing than of an equalizing cause. It follows that any change in the distribution of land and water must affect climate, more espe- cially if it changes the character or course of the ocean currents. Turning to the Atlantic, in this connection we perceive that its present condition is peculiar and exceptional. On the one hand it is widely open to the Arctic Sea and the influence of its cold currents, and on the other it is supplied with a heating apparatus of enormous power to give a special elevation of temperature, more particularly to its eastern coasts. The great equatorial current running across from Africa is on its northern side embayed in the Gulf of Mexico, as in a great 82 THE HISTORY OF THE NORTH ATLANTIC cauldron, and pouring through the mouth of this in the Bahama channel, forms the gulf stream, which, widening out like a fan, forms a vast expanse of warm water, from which the pre- vailing westerly winds of the North Atlantic waft a constant supply of heated moist air to the western coasts of Europe, giving them a much more warm and uniform climate than that which prevails in similar latitudes in Eastern America, where the cold Arctic currents hug the shore, and bring down ice from Baffin's Bay. Now all this might be differently arranged. We shall find that there were times, when the Isthmus of Panama being broken through, there was no Gulf Stream, and Norway and England were reduced to the conditions of Greenland and Labrador, and when refrigeration was still further increased by subsidence of northern lands affording freer sweep to the Arctic currents. On the other hand, there were times when the Gulf of Mexico extended much farther north than at present, and formed an additional surface of warm water to heat all the interior of America, as well as the Atlantic. Geo- graphical changes of these kinds, have probably given us the glacial period in very recent times, and at an earlier era those warm climates which permitted temperate vegetation to flourish as far north as Greenland. These are, however, great topics, which must form the subject of other chapters. I am old enough to remember the sensation caused by the delightful revelations of Edward Forbes respecting the zones of animal life in the sea, and the vast insight which they gave into the significance of the work on minute organisms pre- viously done by Ehrenberg, Lonsdale and Williamson, and into the meaning of fossil remains. A little later the sound- ings for the Atlantic cable revealed the chalky foraminiferal ooze of the abyssal ocean. Still more recently, the wealth of facts disclosed by the Challenger voyage, which naturalists have scarcely yet had time to digest, have opened up to us new worlds of deep-sea life. THE HISTORY OF THE NORTH ATLANTIC 83 The bed of the deep Atlantic is covered, for the most part, by a mud or ooze, largely made up of the debris of foramini- fera and other minute organisms mixed with fine clay. In the North Atlantic the Norwegian naturalists call this the Biloculina mud. Farther south, the Challenger naturalists speak of it as Globigerina ooze. In point of fact it contains different species of foraminiferal shells, Globigerina and Orbulina being in some localities dominant, and in others, other species ; and these changes are more apparent in the shallower portions of the ocean. On the other hand, there are means for disseminating coarse material over parts of the ocean beds. There are, in the line of the Arctic current, on the American coast, great sand banks, and off the coast of Norway, sand constitutes a considerable part of the bottom material. Soundings and dredgings off Great Britain, and also off the American coast, have shown that fragments of stone referable to Arctic lands are abundantly strewn over the bottom, along certain lines, and the Antarctic continent, otherwise almost unknown, makes its presence felt to the dredge by the abundant masses of crystalline rock drifted far from it to the north. These are not altogether new discoveries. I had inferred, many years ago, from stones taken up by the hooks of fishermen on the banks of Newfoundland, that rocky material from the north is dropped on these banks by the heavy ice which drifts over them every spring, that these are glaciated, and that after they fall to the bottom sand is drifted over them with sufficient velocity to polish the stones, and to erode the shelly coverings of Arctic animals attached to them. 1 If, then, the Atlantic basin were upheaved into land, we should see beds of sand, gravel and boulders with clay flats and layers of marl and limestone. According to the Challenger reports, in the Antarctic seas S. of 64 there is blue mud, with fragments of rock, in depths 1 "Notes on Post-Pliocine of Canada," 1872. 84 THE HISTORY OF THE NORTH ATLANTIC of 1,200 to 2,000 fathoms. The stones, some of them glaci- ated, were granite, diorite, amphibolite, mica schist, gneiss and quartzite. This deposit ceases and gives place to Globigerina ooze and red clay at 46 to 47 S., but even farther north there is sometimes as much as 49 per cent, of crystalline sand. In the Labrador current a block of syenite, weighing 400 Ibs., was taken up from 1,340 fathoms, and in the Arctic current, 100 miles from land, was a stony deposit, some stones being glaciated. Among these were smoky quartz, quartzite, lime- stone, dolomite, mica schist, and serpentine ; also particles of monoclinic and triclinic felspar, hornblende, augite, magnetite, mica and glauconite, the latter, no doubt, formed in the sea bottom, the others drifted from Eozoic and Palaeozoic forma- tions to the north. 1 A remarkable fact in this connection is that the great depths of the sea are as impassable to the majority of marine animals as the land itself. According to Murray, while twelve of the Challenger's dredgings, taken in depths greater than 2,000 fathoms, gave 92 species, mostly new to science, a similar number of dredgings in shallower water near the land, give no less than 1,000 species. Hence arises another apparent para- dox relating to the distribution of organic beings. While at first sight it might seem that the chances of wide distribution are exceptionally great for marine species, this is not so. Ex- cept in the case of those which enjoy a period of free locomo- tion when young, or are floating and pelagic, the deep ocean sets bounds to their migrations. . On the other hand, the spores of cryptogamic plants may be carried for vast distances by the wind, and the growth of volcanic islands may effect connections which, though only temporary, may afford oppor- tunity for land animals and plants to pass over. With reference to the transmission of living beings across the Atlantic, we have before us the remarkable fact that from 1 General Report, " Challenger" Expedition. THE HISTORY OF THE NORTH ATLANTIC 85 the Cambrian age onwards there were, on the two sides of the ocean, many species of invertebrate animals which were either identical or so closely allied as to be possibly varietal forms, in- dicating probably the shallowness of the ocean in these periods. In like manner, the early plants of the Upper Silurian, Devo- nian, and Carboniferous present many identical species ; but this identity is less marked in more modern times. Even in the latter, however, there are remarkable connections between the floras of oceanic islands and the continents. Thus the Bermudas, altogether recent islands, have been stocked by the agency chiefly of the ocean currents and of birds, with nearly 150 species of continental plants; and the facts col- lected by Helmsley as to the present facilities of transmission, along with the evidence afforded by older oceanic islands which have been receiving animal and vegetable colonists for longer periods, go far to show that, time being given, the sea actually affords facilities for the migration of the in- habitants of the land, comparable with those of continuous continents. In so far as plants are concerned, it is to be observed that the early forests were largely composed of cryptogamous plants, and the spores of these in modern times have proved capable of transmission from great distances. In considering this, we cannot fail to conclude, that the union of simple cryp- togamous fructification with arboreal stems of high complexity, so well illustrated by Dr. Williamson, had a direct relation to the necessity for a rapid and wide distribution of these ancient trees. It seems also certain that some spores, as, for example, those of the Rhizocarps, 1 a type of vegetation abundant in the Palaeozoic, and certain kinds of seeds, as those named sEthoetesta and Pachytheca, were fitted for flotation. Further, the periods of Arctic warmth permitted the passage around 1 See paper by the author on Palaeozoic Rhizocarps, Chicago Trans., 1886. 86 THE HISTORY OF THE NORTH ATLANTIC the northern belt of many temperate species of plants, just as now happens with the Arctic flora ; and when these were dis- placed by colder periods, they marched southward along both sides of the sea on the mountain chains. The same remark applies to northern forms of marine inver- tebrates, which are much more widely distributed in longitude than those farther south. The late Mr. Gywn Jeffreys, in one of his latest communications on this subject, stated that 54 per cent, of the shallow-water mollusks of New England and Canada are also European, and of the deep-sea forms, 30 out of 35 ; these last, of course, enjoying greater facilities for migration than those which have to travel slowly along the shallows of the coast in order to cross the ocean and settle themselves on both sides. Many of these animals, like the common mussel and sand clam, are old settlers which came over in the Pleistocene period, or even earlier. Others, like the common periwinkle, seem to have been slowly extending them- selves in modern times, perhaps even by the agency of man. The older immigrants may possibly have taken advantage of lines of coast now submerged, or of warm periods, when they could creep round the Arctic shores. Mr. Herbert Carpenter and other naturalists employed on the Challenger collections have made similar statements respecting other marine inverte- brates, as, for instance, the Echinoderms, of which the deep- sea crinoids present many common species, and my own collec- tions prove that many of the shallow-water forms are common. Ball and Whiteaves 1 have shown that some mollusks and Echinoderms are common even to the Atlantic and Pacific coasts of North America ; a remarkable fact, testifying at once to the fixity of these species and to the manner in which they have been able to take advantage of geographical changes. Some of the species of whelks common to the Gulf of St. Lawrence and the Pacific are animals which have no special 1 Ball, Report on Alaska ; Whiteaves, Trans. R. S. C. THE HISTORY OF THE NORTH ATLANTIC 87 locomotive powers, even when young, but they are northern forms not proceeding far south, so that they may have passed through the Arctic seas. In this connection it is well to re- mark that many species of animals have powers of locomotion in youth which they lose when adult, and that others may have special means of transit. I once found at Gaspe a specimen of the Pacific species of Coronula, or whale-barnacle, the C. regince of Darwin, attached to a whale taken in the Gulf of St. Lawrence, and which had possibly succeeded in making that passage around the north of America which so many navigators have essayed in vain. 1 But it is to be remarked that while many plants and marine invertebrates are common to the two sides of the Atlantic, it is different with land animals, and especially vertebrates. I do not know that any palaeozoic insects or land snails or millipedes of Europe and America are specifically identical, and of the numerous species of batrachians of the Carboniferous and reptiles of the Mesozoic, all seem to be distinct on the two sides. The same appears to be the case with the Tertiary mammals, until in the later stages of that great period we find such genera as the horse, the camel, and the elephant appear- ing on the two sides of the Atlantic ; but even then the species seem different, except in the case of a few northern forms. Some of the longer-lived mollusks of the Atlantic furnish suggestions which remarkably illustrate the biological aspect of these questions. Our familiar friend the oyster is one of these. The first-known oysters appear in the Carboniferous in Belgium and in the United States of America. In the Carboniferous and Permian they are few and small, and they do not culminate till the Cretaceous, in which there are no less than ninety-one so-called species in America alone ; but some of the largest known species are found in the Eocene. The oyster, though 1 I am informed, however, that the Coronula is found also in the Bis- cayan whales. 88 THE HISTORY OF THE NORTH ATLANTIC an inhabitant of shallow water, and very limitedly locomotive when young, has survived all the changes since the Carbon- iferous age, and has spread itself over the whole northern hemisphere, 1 though a warm water rather than Arctic type. I have collected fossil oysters in the Cretaceous clays of the coulees of Western Canada, in the Lias shales of England, in the Eocene and the Cretaceous beds of the Alps, of Egypt, of the Red Sea coast, of Judea, and the heights of Lebanon. Everywhere and in all formations they present forms which are so variable and yet so similar that one might suppose all the so-called species to be mere varieties. Did the oyster originate separately on the two sides of the Atlantic, or did it cross over so promptly that its appearance seems to be identical on the two sides ? Are all the oysters of a common ancestry, or did the causes, whatever they were, which introduced the oyster in the Carboniferous act over again in later periods ? Who can tell ? This is one of the cases where causation and develop- ment the two scientific factors which constitute the basis of what is called evolution cannot easily be isolated. I would recommend to those biologists who discuss these questions to devote themselves to the oyster. This familiar mollusk has successfully pursued its course, and has overcome all its enemies, from the flat-toothed selachians of the Carboniferous to the oyster dredges of the present day, has varied almost indefinitely, and yet has continued to be an oyster, unless, indeed, it may at certain portions of its career have temporarily assumed the guise of a Gryphaea or an Exogyra. The history of such an animal deserves to be traced with care, and much curious in- formation respecting it will be found in the report which I have cited in the note. But in these respects the oyster is merely an example of many forms. Similar considerations apply to all those Pliocene and Pleistocene mollusks which are found in the raised sea 1 White, Report U. S. Geol. Survey, 1882-83. THE HISTORY OF THE NORTH ATLANTIC 89 bottoms of Norway and Scotland, on the top of Moel Tryfaen, in Wales, and at similar great heights on the hills of America, many of which can be traced back to early Tertiary times, and can be found to have extended themselves over all the seas of the northern hemisphere. They apply in like manner to the ferns, the conifers, and the broad-leaved trees, many of which we can now trace without specific change to the Eocene and Cretaceous. They all show that the forms of living things are more stable than the lands and seas in which they live. If we were to adopt some of the modern ideas of evolution, we might cut the Gordian knot by supposing that, as like causes produce like effects, these types of life have originated more than once in geological time, and need not be genetically connected with each other. But while evolutionists repudiate such an appli- cation of their doctrine, however natural and rational, it would seem that nature still more strongly repudiates it, and will not allow us to assume more than one origin for one species. Thus the great question of geographical distribution remains in all its force ; and, by still another of our geological paradoxes, mountains become ephemeral things in comparison with the delicate herbage which covers them, and seas are in their pre- sent extent but of yesterday, when compared with the minute and feeble organisms that creep on their sands or swim in their waters. The question remains : Has the Atlantic achieved its des- tiny and finished its course, or are there other changes in store for it in the future? The earth's crust is now thicker and stronger than ever before, and its great ribs of crushed and folded rock are more firm and rigid than in any previous period. The stupendous volcanic phenomena manifested in Mesozoic and early Tertiary times along the borders of the Atlantic have apparently died out. These facts are in so far guarantees of permanence. On the other hand, it is known that move- ments of elevation, along with local depression, are in progress QO THE HISTORY OF THE NORTH ATLANTIC in the Arctic regions, and a great weight of new sediment is being deposited along the borders of the Atlantic, especially on its western side ; and this is not improbably connected with the earthquake shocks and slight movements of depression which have occurred in North America. It is possible that these slight and secular movements may go on uninterruptedly, or with occasional paroxysmal disturbances, until considerable changes are produced. It is possible, on the other hand, that after the long period of quiescence which has elapsed, there may be a new settlement of the ocean bed, accompanied with foldings of the crust, es- pecially on the western side of the Atlantic, and possibly with renewed volcanic activity on its eastern margin. In either case, a long time relatively to our limited human chronology may intervene before the occurrence of any marked change. On the whole, the experience of the past would lead us to ex- pect movements and eruptive discharges in the Pacific rather than in the Atlantic area. It is therefore not unlikely that the Atlantic may remain undisturbed, unless secondarily and in- directly, until after the Pacific area shall have attained to a greater degree of quiescence than at present. But this subject is one too much involved in uncertainty to warrant us in follow- ing it farther. In the meantime the Atlantic is to us a practically permanent ocean, varying only its tides, its currents, and its winds, which science has already reduced to definite laws, so that we can use if we cannot regulate them. It is ours to take advantage of this precious time of quietude, and to extend the blessings of science and of our Christian civilisation from shore to shore, until there shall be no more sea, not in the sense of that final drying-up of old ocean to which some physicists look forward, but in the higher sense of its ceasing to be the emblem of un- rest and disturbance, and the cause of isolation. I must now close this chapter with a short statement of some THE HISTORY OF THE NORTH ATLANTIC QI general truths which I have had in view in directing attention to the geological development of the Atlantic. We cannot, I think, consider the topics to which I have referred with- out perceiving that the history of ocean and continent is an example of progressive design, quite as much as that of living beings. Nor can we fail to see that, while in some important directions we have penetrated the great secret of nature, in reference to the general plan and structure of the earth and its waters, and the changes through which they have passed, we have still very much to learn, and perhaps quite as much to unlearn, and that the future holds out to us and to our suc- cessors higher, grander, and clearer conceptions than those to which we have yet attained. The vastness and the might of ocean and the manner in which it cherishes the feeblest and most fragile beings, alike speak to us of Him who holds it in the hollow of His hand, and gave to it of old its boundaries and its laws ; but its teaching ascends to a higher tone when we consider its origin and history, and the manner in which it has been made to build up continents and mountain-chains, and, at the same time, to nourish and sustain the teeming life of sea and land. REFERENCES : Presidential Address to the British Association for the Advancement of Science, Birmingham, 1886. " Geology of Nova Scotia, New Brunswick, and Prince Edward Island." Fourth Edition, London, 1891. S. E. THE DAWN OF LIFE. DEDICATED TO THE MEMORY OF SIR WILLIAM E. LOGAN, THE UNWEARIED EXPLORER OF THE LAURENTIAN ROCKS, AND THE FOUNDER OF THE GEOLOGICAL SURVEY OF CANADA. WHAT ARE THE OLDEST ROCKS, AND WH-ERE ? CONDITIONS OF THEIR FORMATION INDICATIONS OF LIFE WHAT ITS PROBABLE NATURE NATURE-PRINT OF EOZOON, showing laminated, acervuline, and fragmental portions. This is printed from an electrotype taken from an etched slab of Eozoon, and not touched with a graver except to remedy some accidental flaws in the plate. The diagonal white line marks the course of a calcite vein. CHAPTER V. THE DAWN OF LIFE DO we know the first animal ? Can we name it, explain its structure, and state its relations to its successors ? Can we do this by inference from the succeeding types of being ; and if so, do our anticipations agree with any actual reality disinterred from the earth's crust ? If we could do this , either by inference or actual discovery, how strange it would be to know that we had before us even the remains of the first creature that could feel or will, and could place itself in vital relation with the great powers of inanimate nature. If we believe in a Creator, we shall feel it a solemn thing to have access to the first creature into which He breathed the breath of life. If we hold that all things have been evolved from collision of dead forces, then the first molecules of matter which took upon themselves the responsibility of living, and, aiming at the enjoyment of happiness, subjected themselves to the dread alternatives of pain and mortality, must surely evoke from us that filial reverence which we owe to the authors of our own being ; if they do not involuntarily draw forth even a superstitious adoration. The veneration of the old Egyptian for his sacred animals would be a comparatively reasonable idolatry, if we could imagine any of these animals to have been the first that emerged from the domain of dead matter, and the first link in a reproductive chain of being that produced all the population of the world. Independently of any such hypotheses, all students of nature must regard with surpassing 96 THE DAWN OF LIFE interest the first bright streaks of light that break on the long reign of primeval night and death, and presage the busy day of teeming animal existence. No wonder, then, that geologists have long and earnestly groped in the rocky archives of the earth in search of some record of this patriarch of the animal kingdom. But after long and patient research there still remained a large residuum of the oldest rocks destitute of all traces of living beings, and designated by the hopeless name "Azoic," the formations destitute of remains of life, the stony records of a lifeless world. So the matter remained till the Laurentian rocks of Canada, lying at the base of these old Azoic formations, afforded forms believed to be of organic origin. The dis- covery was hailed with enthusiasm by those who had been prepared by previous study to receive it. It was regarded with feeble and not very intelligent faith by many more, and was met with half-concealed or open scepticism by others. It pro- duced a copious crop of descriptive and controversial literature, but for the most part technical, and confined to scientific trans- actions and periodicals, read by very few except specialists. Thus, few even of geological and biological students have clear ideas of the real nature and mode of occurrence of these ancient organisms, if organisms they are, and of their relations to better known forms of life ; while the crudest and most in- accurate ideas have been current in lectures and popular books, and even in text-books. This state of things has long ceased to be desirable in the interests of science, since the settlement of the questions raised is in the highest degree important to the history of life. We cannot, it is true, affirm that Eozoon is in reality the long- sought prototype of animal existence; but it was /or us, at least until recently, the last organic foothold, on which we can poise ourselves, that we may look back into the abyss of the infi- nite past, and forward to the long and varied progress of life in THE DAWN OF LIFE 97 geological time. Now, however, we have announcements to be referred to in the sequel of other organisms discovered in the so-called Archaean rocks ; and it is not improbable that these will rapidly increase. The discussion of its claims have also raised questions and introduced new points, certain, if properly entered into, to be fruitful of interesting and valuable thought, and to form a good introduction to the history of life in con- nection with geology. As we descend in depth and time into the earth's crust, after passing through nearly all the vast series of strata consti- tuting the monuments of geological history, we at length reach the Eozoic or Laurentian rocks, 1 deepest and oldest of all the formations known to the geologist, and more thoroughly altered or metamorphosed by heat and heated moisture than any others. These rocks, at one time known as Azoic, being sup- posed destitute of all remains of living things, but now more properly Eozoic, are those in which the first bright streaks of the dawn of life make their appearance. The name Laurentian, given originally to the Canadian development of these rocks by Sir William Logan, but now applied to them throughout the world, is derived from a range of hills lying north of the St. Lawrence valley, which the old French geographers named the Laurentides. In these hills the harder rocks of this old formation rise to considerable heights, and form the highlands separating the St. Lawrence valley from the great plain fronting on Hudson's Bay and the Arctic Sea. At first sight it may seem strange that rocks so ancient should anywhere appear at the surface, especially on the tops of hills ; but this is a necessary result of the mode of formation of our continents. The most ancient sediments deposited in the sea were those first elevated into land, and first altered and hardened. Upheaved in the folding of the earth's crust into high and rugged ridges, they have either re- 1 Otherwise named "Archaean." 98 THE DAWN OF LIFE mained uncovered with newer sediments, or have had such as were deposited on them washed away ; and being of a hard and resisting nature, they have remained comparatively unworn when rocks much more modern have been swept off by denud- ing agencies. 1 But the exposure of the old Laurentian skeleton of mother earth is not confined to the Laurentide Hills, though these have given the formation its name. The same ancient rocks appear in the Adirondack mountains of New York, and in the patches which at lower levels protrude from beneath the newer formations along the American coast from Newfoundland to Maryland. The older gneisses of Norway, Sweden, and the Hebrides, of Bavaria and Bohemia, of Egypt, Abyssinia and Arabia, belong to the same age, and it is not unlikely that similar rocks in many other parts of the old continent will be found to be of as great antiquity. In no part of the world, however, are the Laurentian rocks more extensively distributed or better known than in Canada ; and to this as the grandest and most instructive development of them we may more especially devote our attention. The Laurentian rocks, associated with another series only a little younger, the Huronian, form a great belt of broken and hilly country, extending from Labrador across the north of Canada to Lake Superior, and thence bending northward to the Arctic Sea. Everywhere on the lower St. Lawrence they appear as ranges of billowy rounded ridges on the north side of the river, and as viewed from the water or the southern shore, especially when sunset deepens their tints to blue and violet, they present a grand and massive appearance, which, in the eye of the geologist, who knows that they have endured the battles and the storms of time longer than any other moun- 1 This implies the permanence of continents in their main features, a doctrine the writer has maintained for thirty years, and which is discussed elsewhere. THE DAWN OF LIFE 99 tains, invests them with the dignity which their mere elevation would fail to give. (Fig. i.) In the isolated mass of the Adirondacks, south of the Canadian frontier, they rise to a still greater elevation, and form an imposing mountain group, almost equal in height to their somewhat more modern rivals, the White Mountains, which face them on the opposite side of Lake Champlain. The grandeur of the old Laurentian ranges is, however, best displayed where they have been cut across by the great trans- verse gorge of the Saguenay, arid where the magnificent preci- pices, known as Capes Trinity and Eternity, look down from their elevation of 1,500 feet on the fiord, which at their feet is more than 100 fathoms deep. The name Eternity applied to such a mass is geologically scarcely a misnomer, for it dates back to the very dawn of geological time, and is of hoar antiquity in comparison with such upstart ranges as the Andes and the Alps. (See Frontispiece.) On a nearer acquaintance, the Laurentian country appears as a broken and hilly upland and highland district, clad in its pristine state with magnificent forests, but affording few attrac- tions to the agriculturist, except in the valleys, which follow the lines of its softer beds, while it is a favourite region for the angler, the hunter, and the lumberman. Many of the Lauren- tian townships of Canada are, however, already extensively settled, and the traveller may pass through a succession of more or less cultivated valleys, bounded by rocks or wooded hills and crags, and diversified by running streams and roman- tic lakes and ponds, constituting a country always picturesque and often beautiful, and rearing a strong and hardy population. To the geologist it presents in the main immensely thick beds of gneiss, bedded diorite and quartzite, and similar crystalline rocks, contorted in the most remarkable manner, so that if they could be flattened out they would serve as a skin much too large for mother earth in her present state, so much has IOO THE DAWN OF LIFE THE DAWN OF LIFE IOI she shrunk and wrinkled since those ^ ^ youthful days when the Laurentian rocks were her outer covering. o I cannot describe such rocks, but their c - names, as given in the section, Fig. 2, will tell something to those who have any knowledge of the older crystalline materials of the earth's crust. To those ^ who have not, I would advise a visit to some cliff on the lower St. Lawrence, or ) Limestone with Eozoon. (c) Diorite and Gneiss. tected by a ridge of gneiss, rises in an abrupt wooded bank by the roadside, and a little farther forms a bare white promontory, projecting into the fields. The limestone is here highly inclined and much contorted, and in all the excavations a thickness of about 100 feet of it may be exposed. It is white and crystalline, varying much, however, in coarseness in different bands. It is in some layers pure and white ; in others it is traversed by many grey layers of gneissose and other matter, or by irregular bands and nodules of pyroxene and serpentine, and it contains subordinate beds of dolomite. In one layer only, and this but a few feet thick, does the Eozoon occur in abundance in a perfect state, though 10 THE DAWN OF LIFE fragments and imperfectly preserved specimens abound in other parts of the bed. It is a great mistake to suppose that it constitutes whole beds of rock in an uninterrupted mass. Its true mode of occurrence is best seen on the weathered sur- faces of the rock, where the serpentinous specimens project in irregular patches of various sizes, sometimes twisted by the contortion of the beds, but often too small to suffer in this way. On such surfaces the projecting patches of the fossil exhibit laminae of serpentine so precisely like the Stromatoporce of the Silurian rocks, that any collector would pounce upon them at once as fossils. In some places these small weathered speci- mens can be easily chipped off from the crumbling surface of the limestone ; and it is perhaps to be regretted that they have not been more extensively shown to palaeontologists, with the cut slices which to many of them are so problematical. One of the original specimens, brought from the Calumet, and now in the Museum of the Geological Survey of Canada, was of this kind, and much finer specimens from Cote St. Pierre are now in that collection and in my own. A very fine example is represented on the plate facing this chapter, which is taken from an original photograph. In some of the layers are found other and more minute vesicular forms, which may be organic, and these, together with fragmental remains, as ingredients in the limestone, will be discussed in the sequel. We may merely notice here that the most abundant layer of Eozoon at this place occurs near the base of the great limestone band, and that the upper layers, in so far as seen, are less rich in it. Further, there is no necessary connection between Eozoon and the occurrence of serpentine, for there are many layers full of bands and lenticular masses of that mineral without any Eozoon except occasional fragments, while the fossil is some- times partially mineralised with pyroxene, dolomite, or common limestone. The section in Fig. 4 will serve to show the atti- tude of the limestone at this place, while the more general THE DAWN OF LIFE III section, Fig. 2, page 101, taken from Sir William Logan, shows its relation to the other Laurentian rocks. We may now notice the manner in which the specimens discovered in this and other places in the Laurentian country came to be regarded as organic. It is a trite remark that most discoveries are made, not by one person, but by the joint exertions of many, and that they have their preparations made often long before they actually appear. For this reason I may be excused here for introducing some personal details in relation to the discovery of Eozoon, and which are indeed necessary in vindication of its claims. In this case the stable foundations were laid years before the discovery of Eozoon, by the careful surveys made by Sir William Logan and his assistants, and the chemical examination of the rocks and minerals by Dr. Sterry Hunt, which established beyond all doubt the great age and truly bedded character of the Lauren- tian rocks and their probable original nature, and the changes which they have experienced in the course of geological time. On the other hand, Dr. Carpenter and others in England were examining the structure of the shells of the humbler inhabitants of the modern ocean, and the manner in which the pores of their skeletons become infiltrated with mineral matter when deposited in the sea bottom. These laborious and apparently dissimilar branches of scientific inquiry were destined to be united by a series of happy discoveries, made not fortuitously but by painstaking and intelligent observers. The discovery of the most ancient fossil was thus not the chance picking up of a rare and curious specimen. It was not likely to be found in this way ; and if so found, it would have remained unnoticed and of no scientific value, but for the accumulated stores of zoological and palaeontological knowledge, and the surveys previously made, whereby the age and distribution of the Laurentian rocks and the chemical conditions of their deposi- tion and metamorphism were ascertained. 112 THE DAWN OF - LIFE The first specimens of Eozoon ever procured, in so far as known, were collected at Burgess, in Ontario, by a veteran Canadian mineralogist, Dr. Wilson, of Perth, and were sent to Sir William Logan as mineral specimens. Their chief interest at that time lay in the fact that certain laminae of a dark green mineral present in the specimens were found, on analysis by Dr. Hunt, to be composed of a new hydrous silicate, allied to serpen- tine, and which he named loganite. The form of this mineral was not suspected to be of organic origin. Some years after, in 1858, other specimens, differently mineralized with the minerals serpentine and pyroxene, were found by Mr. J. McMullen, an explorer in the service of the Geological Survey, in the limestone of the Grand Calumet on the River Ottawa. These seem to have at once struck Sir W. E. Logan as resembling the Silurian fossils known as Stromatopora, and he showed them to Mr. Billings, the palaeontologist of the survey, and to the writer, with this suggestion, confirming it with the sagacious consideration that inasmuch as the Ottawa and Burgess speci- mens were mineralized by different substances, yet were alike in form, there was little probability that they were merely mineral or concretionary. Mr. Billings was naturally unwilling to risk his reputation in affirming the organic nature of such specimens ; and my own suggestion was that they should be sliced, and examined microscopically, and that if fossils, as they presented merely concentric laminae and no cells, they would probably prove to be protozoa rather than corals. A few slices were accordingly made, but no definite structure could be detected. Nevertheless, Sir William Logan took some of the specimens to the meeting of the American Association at Springfield, in 1859, and exhibited them as possibly Laurentian fossils ; but the announcement was evidently received with some incredulity. In 1862 they were exhibited by Sir William to some geological friends in London, but he remarks that "few seemed disposed to believe in their organic character, FIG. i. FIG. 2. FIG. 3. FIG. i. SMALL SPECIMEN OF EOZOON, weathered out, natural size, from a photograph. FIG. 2. CANAL SYSTEM OF EOZOON injected with serpentine (magni- fied). FIG. 3. VERY FINE CANALS AND TUBULI filled with Dolomite (magni- fied). (From Micro-photographs.) THE DAWN OF LIFE with the exception of my friend, Professor Ramsay." In 1863 the general Report of the Geological Survey, summing up its FIG. 5. Weathered Specimen of Eozoon from the Calumet. (Collected by Mr. McMullen.) FIG. 6. Cross Section of the Specimen represented in Fig. 8. The dark parts are the laminae of calcareous matter converging to the outer surface. 114 THE DAWN OF LIFE work to that time, was published, under the name of the " Geology of Canada," and in this, at page 49, will be found two figures of one of the Calumet specimens, here reproduced, and which, though unaccompanied with any specific name or technical description, were referred to as probably Laurentian fossils. (Figs. 5 and 6.) About this time Dr. Hunt happened to mention to me, in connection with a paper on the mineralization of fossils which he was preparing, that he proposed to notice the mode of preservation of certain fossil woods and other things with which I was familiar, and that he would show me the paper in proof, in order that I might give him any suggestions that occurred to me. On reading it, I observed, among other things, that he alluded to the supposed Laurentian fossils, under the impression that the organic part was represented by the serpentine or loganite, and that the calcareous matter was the filling of the chambers. I took exception to this, stating that though in the slices I had examined no structure was apparent, still my impression was that the calcareous matter was the fossil, and the serpentine or loganite the filling. He said " In that case, would it not be well to re-examine the specimens, and try to discover which view is correct ? " He mentioned, at the same time, that Sir William had recently shown him some new and beautiful specimens collected by Mr. Lowe, one of the explorers on the staff of the Survey, from a third locality, at Grenville, on the Ottawa. It was supposed that these might throw further light on the subject ; and accordingly Dr. Hunt suggested to Sir William to have additional slices of these new specimens made by Mr. Weston, of the Survey, whose skill as a preparer of these and other fossils has often done good service to science. A few days thereafter some slices were sent to me, and were at once put under the microscope. I was delighted to find in one of the first specimens examined a beautiful group of tubuli penetrating THE DAWN OF LIFE one of the calcite layers. Here was evidence, not only that the calcite layers represented the true skeleton of the fossil, but also of its affinities with the foraminifera, whose tubulated supplemental skeleton, as described and figured by Dr. Car- penter, and represented in specimens in my collection, pre- sented by him, was apparently of the same type with that preserved in the canals of these ancient fossils. Fig. 7 is an accurate representation of the group of canals first detected by me. FIG. 7. Group of Canals in the Supplemental Skeleton of Eozoon. Taken from the specimen in which they were first recognised. Magnified. (Camera tracing by Mr. H. S. Smith.) On showing the structures discovered to Sir William Logan, he entered into the matter with enthusiasm, and had a great number of slices, as well as decalcified specimens, prepared, which were placed in my hands for examination. Feeling that the discovery was most important, but that it would be met with determined scepticism by a great many geologists, I was not content with examining the typical speci- mens of Eozoon, but had slices prepared of every variety of Il6 THE DAWN OF LIFE Laurentian limestone, of altered limestones from the Primordial and Silurian, and of serpentine marbles of all the varieties furnished by our collections. They were examined with ordi- nary and polarized light, and with every variety of illumination. They were also examined as decalcified specimens, after the carbonate of lime had been removed by acids. An extensive series of notes and camera tracings were made of all the appearances observed; and of some of the more important structures beautiful drawings were executed by the late Mr. H. S. Smith, the then palseontological draughtsman of the Survey. The result of the whole investigation was a firm con- viction that the structure was organic and foraminiferal, and that it could be distinguished from any merely mineral or crystalline forms occurring in these or other limestones. At this stage of the matter, and after exhibiting to Sir William all the characteristic appearances, in comparison with such concretionary, dendritic and crystalline structures as most resembled them, and also with the structure of recent and fossil Foraminifera, I suggested that the further prosecution of the matter should be handed over to Mr. Billings, as palaeontologist of the Survey. I was engaged in other re- searches, not connected with the Survey or with this particular department, and I knew that no little labour must be devoted to the work and to its publication, and that some controversy might be expected. Mr. Billings, however, with his character- istic caution and modesty, declined. His hands were full of other work. He had not given any special attention to the microscopic appearances of Foraminifera or of mineral sub- stances. It was finally arranged that I should prepare a de scription of the fossil, which Sir William would take to London, along with the more important specimens, and a detailed list stating all the structures observed in each. Sir William was to submit the manuscript and specimens to Dr. Carpenter, or, failing him, to Prof. T. Rupert Jones, in the hope that these THE DAWN OF LIFE eminent authorities would confirm my conclusions, and bring forward new facts which I might have overlooked or been ignorant of. Sir William saw both gentlemen, who gave their testimony in favour of the organic and foraminiferal character of the specimens ; and Dr. Carpenter, in particular, gave much attention to the subject, and worked out more in detail many of the finer structures, besides contributing valuable suggestions as to the probable affinities of the supposed fossil. Dr. Carpenter thus contributed in a very important manner to the perfecting of the investigations begun in Canada, and on him fell the greater part of their illustration and defence, 1 in so far as Great Britain is concerned. The immediate result was a composite paper in the Pro- ceedings of the Geological Society, by Sir W. E. Logan, Dr. Car- penter, Dr. Hunt, and myself, in which the geology, palaeonto- logy and mineralogy of Eozoon Canadense and its containing rocks were first given to the world. 2 It cannot be wondered at that when geologists and palaeontologists were thus required to believe in the existence of organic remains in rocks regarded as altogether Azoic and hopelessly barren of fossils, and to carry back the dawn of life as far before those Primordial rocks, which were supposed to contain its first traces, as these are before the middle period of the earth's life history, some hesita- tion should be felt. Further, the accurate appreciation of the evidence for such a fossil as Eozoon required an amount of knowledge of minerals, of the more humble types of animals, and of the conditions of mineralization of organic remains, pos- sessed by few even of professional geologists. Thus Eozoon has met with some scepticism and not a little opposition, though the latter has been weaker than we might have expected when 1 In Quarterly Journal of Geological Society, vol. xxii. ; Prof. Royal Society ', vol. xv. ; Intellectual Observer, 1865. Annals and Magazine of Natural History, 1874 ; and other papers and notices. 2 Journal Geological Society, February, 1865. Il8 THE DAWN OF LIFE we consider the startling character of the facts adduced, and has mostly come from men imperfectly informed. But what is Eozoon, if really of animal origin ? The shortest answer to this question is, that this ancient fossil is supposed to be the skeleton of a creature belonging to that simple and humbly organized group of animals which are known by the name Protozoa. If we take as a familiar example of these the gelatinous and microscopic creature found in stagnant ponds, and known as the Amoeba l (Fig. 8), it will form a convenient starting-point. Viewed under a low power, it appears as a little patch of jelly, irregular in form, and constantly changing its aspect as it moves, by the extension of parts of its body into finger-like processes or pseudopods which serve as extempore limbs. When moving on the surface of a slip of glass under the microscope, it seems, as it were, to flow along rather than creep, and its body appears to be of a semi-fluid consistency. It may be taken as an example of the least complex forms of animal life known to us, and is often spoken of by naturalists as if it were merely a little particle of living and scarcely organ- ized jelly or protoplasm. When minutely examined, however, it will not be found so simple as it at first sight appears. Its outer layer is clear and transparent, and more dense than the inner mass, which seems granular. It has at one end a curious vesicle which can be seen gradually to expand and become filled with a clear drop of liquid, and then suddenly to contract and expel the contained fluid through a series of pores in the adjacent part of the outer wall. This is the so-called pulsating vesicle, and is an organ both of circulation and excretion. In another part of the body may be seen the nucleus, which is a little cell capable, at certain times, of producing by its division new individuals. Food, when taken in through the wall of the body, forms little pellets, which become surrounded by a 1 The alternating animal, alluding to its change of form. THE DAWN OF LIFE 119 digestive liquid exuded from the enclosing mass into rounded cavities or extemporised stomachs. Minute granules are seen to circulate in the gelatinous interior, and may be substitutes for blood-cells, and the outer layer of the body is capable of protrusion in any direction into long processes, which are very mobile, and used for locomotion and prehension. Further, this creature, though destitute of most of the parts which we are accustomed to regard as proper to animals, seems to exer- cise volition, and to show the same appetites and passions with animals of higher type. I have watched one of these animal- FIG. 8. Amoeba. FIG. 9. Actinophrys. From original sketches. cules endeavouring to swallow a one-celled plant as long as its own body ; evidently hungry and eager to devour the tempting morsel, it stretched itself to its full extent, trying to envelope the object of its desire. It failed again and again ; but renewed the attempt, until at length, convinced of its hopelessness, it flung itself away as if in disappointment, and made off in search of something more manageable. With the Amoeba are found other types of equally simple Protozoa, but somewhat differently s. E. 9 120 THE DAWN OF LIFE organized. One of these, Actinophrys (Fig. 9), has the body globular and unchanging in form, the outer wall of greater thick- ness ; the pulsating vesicle like a blister on the surface, and the pseudopods long and thread-like. Its habits are similar to those of the Amoeba, and I introduce it to show the variations of form and structure possible even among these simple creatures. The Amoeba and Actinophrys are fresh-water animals, and are destitute of any shell or covering. But in the sea there ex- ist swarms of similar creatures, equally simple in organization, but gifted with the power of secreting around their soft bodies beautiful little shells or crusts of carbonate of lime, having one orifice, and often in addition multitudes of microscopic pores through which the soft gelatinous matter can ooze, and form outside finger-like or thread-like extensions for collecting food. In some cases the shell consists of a single cavity only, but in most, after one cell is completed, others are added, forming a series of cells or chambers communicating with each other, and often arranged spirally or otherwise in most beautiful and symmetrical forms. Some of these creatures, usually named Foraminifera, are locomotive, others sessile and attached. Most of them are microscopic, but some grow by multiplication of chambers till they are a quarter of an inch or more in breadth. The original skeleton or primary cell wall of most of these creatures is seen under the miscroscope to be perforated with innumerable pores, and is extremely thin. When, however, owing to the increased size of the shell, or other wants of the creature, it is necessary to give strength, this is done by add- ing new portions of carbonate of lime to the outside, and to these Dr. Carpenter has given the appropriate name of " sup- plemental skeleton " ; and this, when covered by new growths, becomes what he has termed an " intermediate skeleton." The supplemental skeleton is also traversed by tubes, but these are THE DAWN OF LIFE 121 often of larger size than the pores of the cell-wall, and of greater length, and branched in a complicated manner. Thus there are microscopic characters by which these curious shells can be distinguished from those of other marine animals ; and by applying these characters we learn that multitudes of creatures of this type have existed in former periods of the world's history, and that their shells, accumulated in the bottom of the sea, constitute large portions of many limestones. The manner in which such accumulation takes place we learn from what is now going on in the ocean, more especially from the result of the recent deep-sea dredging expeditions. The Foraminifera are vastly numerous, both near the surface and at the bottom of the sea, and multiply rapidly ; and as suc- cessive generations die, their shells accumulate on the ocean bed, or are swept by currents into banks, and thus, in process of time, constitute thick beds of white chalky material, which may eventually be hardened into limestone. This process is now depositing a great thickness of white ooze in the bottom of the ocean ; and in times past it has produced such vast thicknesses of calcareous matter as the chalk and nummulitic limestone of Europe and the orbitoidal limestone of America. The chalk which alone attains a maximum thickness of 1,000 feet, and, according to Lyell, can be traced across Europe for 1,100 geographical miles, may be said to be entirely composed of shells of Foraminifera imbedded in a paste of smaller calcareous bodies, the Coccoliths, which are probably products of marine vegetable life, if not of some animal organism still simpler than the Foraminifera. Lastly, while we have in such modern forms as the masses of Polytrema attached to corals, and the Loftusa of the Eocene and the carboniferous, large fossil foraminiferal species, there is some reason to believe that in the earlier geo- logical ages there existed much larger animals of this grade than are found in our present seas ; and that these, always 122 THE DAWN OF LIFE sessile on the bottom, grew by the addition of successive chambers, in the same manner with the smaller species. 1 Let us, then, examine the structure of Eozoon, taking a typical specimen, as we find it in the limestone of Grenville or Petite Nation. In such specimens the skeleton of the animal is represented by a white crystalline marble, the cavities of the cells by green serpentine, the mode of whose introduction we shall have to consider in the sequel. The lowest layer of ser- pentine represents the first gelatinous coat of animal matter which grew upon the bottom, and which, if we could have seen it before any shell was formed upon its surface, must have resembled a minute patch of living slime. On this primary layer grew a delicate calcareous shell, perforated by innumer- able minute tubuli, and resting on the slimy matter of the animal, though supported also by some perpendicular plates or septa. Upon this again was built up, in order to strengthen it, a thickening or supplemental skeleton, more dense, and desti- tute of fine tubuli, but traversed by branching canals, through which the soft gelatinous matter could pass for the nourish- ment of the skeleton itself, and the extension of pseudopods be- yond it. (Figs. 11,12.) So was formed the first layer of Eozoon, which probably was at its beginning only of very small dimen- sions. On this the process of growth of successive layers of animal sarcode and of calcareous skeleton was repeated again and again, till in some cases even a hundred or more layers were formed (nature-print, Chap. VI.) As the process went on, however, the vitality of the organism became exhausted, prob- ably by the deficient nourishment of the central and lower layers making greater and greater demands on those above, and so the succeeding layers became thinner, and less sup- plemental skeleton was developed. Finally, toward the top, the regular arrangement in layers was abandoned, and the cells 1 I refer to some of the Stromatoporae of the Silurian and the Cryptozoon of the Cambrian. See note appended to this chapter. THE DAWN OF LIFE 123 became a mass of rounded chambers, irregularly piled up in what Dr. Carpenter has termed an " acervuline " manner, and with very thin walls unprotected by supplemental skeleton. Then the growth was arrested, and possibly these upper layers gave off reproductive germs, fitted to float or swim away and to establish new colonies. We may have such reproductive germs in certain curious globular bodies, like loose cells, found in connection with Eozoon in many of the Laurentian lime- FIG. 10. Minute Foraminiferal forms from the Laurentian of Long Lake. Highly magnified, (a) Single cell, showing tubulated wall. (, c ) Portions of same more highly magnified. (d) Serpentine cast of a similar chamber, decalcified, and showing casts of tubuli. stones. 1 At St. Pierre, on the Ottawa, these bodies occur on the surface of layers of the limestone in vast numbers, as if they had been growing separately on the bottom, or had been drifted over it by currents. They may have served as repro- 1 It would be interesting to compare these bodies with the forms re- cently found by Barrois and Cayeux in the "Azoic " quartzite of Brittany, which should certainly now be called Eozoic. 124 THE DAWN OF LIFE ductive buds or germs to establish new colonies of the species. Such was the general mode of growth of Eozoon, and we may now consider more in detail some questions as to its gigantic size, its precise mode of nutrition, the arrangement of its parts, its relations to more modern forms, and the effects of its growth in the Laurentian seas. With respect 'to the size of Eozoon, this was rivalled by some succeeding animals of the same humble type in later geo- logical ages ; and, as a whole, foraminiferal animals have been diminishing in size in the lapse of geological time. This is indeed a fact of so frequent occurrence that it may almost be regarded as a law of the introduction of new forms of life, that they assume in their early history gigantic dimensions, and are afterwards continued by less magnificent species. The relations of this to external conditions, in the case of higher animals, are often complex and difficult to understand ; but in organisms so low as Eozoon and its allies, they lie more on the surface. Such creatures may be regarded as the simplest and most ready media for the conversion of vegetable matter into animal tissues, and their functions are almost entirely limited to those of nutrition. Hence it is likely that they will be able to appear in the most gigantic forms under such conditions as afford them the greatest amount of pabulum for the nourishment of their soft parts and for their skeletons. There is reason to believe, for example, that the occurrence, both in the chalk and the deep-sea mud, of immense quanti- ties of the minute bodies known as Coccoliths along with Foraminifera, is not accidental. The Coccoliths appear to be grains of calcareous matter formed in minute plants adapted to a deep-sea habitat ; and these, along with the vegetable and animal debris constantly being derived from the death of the living things at the surface, afford the material both of sarcode and shell. Now if the Laurentian graphite represents an exuberance of vegetable growth in those old seas propor- THE DAWN OF LIFE 12$ tionate to the great supplies of carbonic acid in the atmosphere and in the waters, and if the Eozoic ocean was even better supplied with salts of lime than those Silurian seas whose vast limestones bear testimony to their richness in such material, we can easily imagine that the conditions may have been more favourable to a creature like Eozoon than those of any other period of geological time. Growing, as Eozoon did, on the floor of the ocean, and covering wide patches with more or less irregular masses, it must have thrown up from its whole surface its pseudopods to seize whatever floating particles of food the waters carried over it. There is also reason to believe, from the outline of certain specimens, that it often grew upward in conical or club- shaped forms, and that the broader patches were penetrated by large pits or oscula, admitting the sea-water deeply into the substance of the masses. In this way its growth might be rapid and continuous ; but it does not seem to have possessed the power of growing indefinitely by new and living layers covering those that had died, in the manner of some corals. Its life seems to have had a definite termination, and when that was reached, an entirely new colony had to be commenced. In this it had more affinity with the Foraminifera, as we now know them, than with the corals, though practically it had the same power with the coral polyps of accumulating limestone in the sea bottom a power indeed still possessed by its fora- miniferal successors. In the case of coral limestones we know that a large proportion of these consist not of continuous reefs, but of fragments of coral mixed with other calcareous organisms, spread usually by waves and currents in continuous beds over the sea bottom. In like manner we find in the limestones containing Eozoon, layers of fragmental matter which show in places the characteristic structures, and which evidently represent the debris swept from the Eozoic masses and reefs by the action of the waves. It is with this frag- 126 THE DAWN OF LIFE mental matter that the small rounded organisms already re- ferred to most frequently occur; and while they may be distinct animals, they may also be the fry of Eozoon, or small portions of its acervuline upper surface floated off in a living state, and possibly capable of living independently and of founding new colonies. It is only by a somewhat wild poetical licence that Eozoon has been represented as a "kind of enormous composite animal stretching from the shores of Labrador to Lake Superior, and thence northward and southward to an unknown distance, and forming masses 1,500 feet in depth." We may, it is true, readily believe in the composite nature of masses of Eozoon, and we see in the corals evidence of the great size to which composite animals of a higher grade can attain. In the case of Eozoon we must imagine an ocean floor more uniform and level than that now existing. On this the organism would establish itself in spots and patches. These might finally be- come confluent over large areas, just as massive corals do. As individual masses attained maturity and died, their pores would be filled up with limestone or silicious deposits, and thus could form a solid basis for new generations, and in this way limestone to an indefinite extent might be produced. Further, wherever such masses were high enough to be attacked by the breakers, or where portions of the sea bottom were elevated, the more fragile parts of the surface would be broken up and scattered widely in beds of fragments over the bottom of the sea, while here and there beds of mud or sand, or of volcanic debris would be deposited over the living or dead organic mass, and would form the layers of gneiss and other schistose rocks interstratified with the Laurentian limestone. In this way, in short, Eozoon would perform a function combining that which corals and Foraminifera perform in the modern seas ; forming both reef limestones and exten- sive chalky beds, and probably living both in the shallow and THE DAWN OF LIFE 127 the deeper parts of the ocean. If in connection with this we consider the rapidity with which the soft, simple, and almost structureless sarcode of these Protozoa can be built up, and the probability that they were more abundantly supplied with food, both for nourishing their soft parts and skeletons, than any similar creatures in later times, we can readily understand the great volume and extent of the Laurentian limestones which they aided in producing. I say aided in producing, because I would not care to commit myself to the doctrine that the Laurentian limestones are wholly of this origin. There may have been other limestone builders than Eozoon, FIG. II. Section of a Nummulite, from Eocene Limestone of Syria. Showing chambers, tubuli, and canals. Compare this and Fig. 12 with Fig. 7 and Nature-print of Eozoon. and there may have been limestones formed by plants like the modern Nullipores, or by merely mineral deposition. Its relations to modern animals of its type have been very clearly denned by Dr. Carpenter. In the structure of its proper wall and its fine parallel perforations, it resembles the Nummulites and their allies ; and the organism may therefore be regarded as an aberrant member of the Nummuline group, which affords some of the largest and most widely distributed of the fossil Foraminifera. This resemblance may be seen in Fig. ii. To the Nummulites it also conforms in its tendency to form a supplemental or intermediate skeleton with canals, 128 THE DAWN OF LIFE though the canals themselves in the arrangement more nearly resemble Calcarina, which is represented in Fig. 12. In its superposition of many layers, and in its tendency to a heaped up or acervuline irregular growth it resembles Polytrema and Tinoporus, forms of a different group in so far as shell-struc- ture is concerned. It may thus be regarded as a composite type, combining peculiarities now observed in two groups, or it may be regarded as representing one of these in another series. At the time when Dr. Carpenter stated these FIG. 12. Portion of shell of Calcarina. Magnified, after Carpenter, (a) Cells. (b) Original cell wall with tubuli. (c) Supplementary skeleton with canals. affinities, it might be objected that Foraminifera of these families are in the main found in the modern and Tertiary periods. Dr. Carpenter has since shown that the curious x>val Foraminifer called Fusulina, found in the coal formation, is allied to both Nummulites and Rotalines ; and Mr. Brady has discovered a true Nummulite in the Lower Carboniferous of Belgium. I have myself found small Foraminifera in the Silurian and Cambro-Silurian of Canada. This group being THE DAWN OF LIFE 1 29 now brought down to the Palaeozoic, we may hope to trace it to the Primordial, and thus to bring it still nearer to Eozoon in time. Though Eozoon was probably not the only animal of the Laurentian seas, yet it was in all likelihood the most con- spicuous and important as a collector of calcareous matter, rilling the same place afterwards occupied by the reef-building corals. Though probably less efficient than these as a con- structor of solid limestones, from its less permanent and con- tinuous growth, it formed wide floors and patches on the sea bottom, and when these were broken up, vast quantities of limestone were formed from their debris. It must also be borne in mind that Eozoon was not everywhere infiltrated with ser- pentine or other silicious minerals ; quantities of its substance were merely filled with carbonate of lime, resembling the chamber wall so closely that it is nearly impossible to make out the difference, and thus is likely to pass altogether unobserved by collectors, and to baffle even the microscopist. Although, therefore, the layers which contain well characterised Eozoon are few and far between, there is reason to believe that in the composition of the limestones of the Laurentian it bore no small part, and as these limestones are some of them several hundred feet in thickness, and extend over vast areas, Eozoon may be supposed to have been as efficient a world-builder as the Stromatoporae of the Silurian and Devonian, the Globi- gerinae and their allies in the chalk, or the Nummulites and Miliolites in the Eocene. It is a remarkable illustration of the constancy of natural causes and of the persistence of animal types, that these humble Protozoans, which began to secrete calcareous matter in the Laurentian period, have been continuing their work in the ocean through all the geological ages, and are still busy in accumulating those chalky muds with which recent dredging operations in the deep sea have made us so familiar. (See Note appended.) All this seems sufficiently reasonable, more especially since I3O THE DAWN OF LIFE no mineralogist has yet succeeded in giving a feasible inor- ganic explanation of the combination of canals, laminae, tubu- lation and varied mineral character existing in Eozoon. But then comes the strange fact of its apparent isolation with- out companions in highly crystalline rocks, and with appa- rently no immediate successors. This has staggered many, and it certainly, if taken thus baldly, seems in some degree improbable. Recent discoveries, however, are removing this reproach from Eozoon. The Laurentian rocks have yielded other varieties, or perhaps species of the genus, those which I have described as variety Acervulina, and variety Minor, and still another form, more like a Stromatopora, which I have provisionally named E. latior^ from the breadth and uniformity of its plates. 1 There are also in the Laurentian limestone cylindrical bodies apparently originally tubular, and with the sides showing radiating markings in the manner of corals, or of the curious Cambrian Archaeocyathus. Matthew, a most careful observer, has found in the Laurentian limestone of New Brunswick certain laminated bodies of cylindrical form, constituting great reefs in the limestone, and in the slates linear flat objects resembling Algae or Graptolites, and spicular structures resembling those of sponges. 2 Britton has also de- scribed from the Laurentian limestone of New Jersey certain ribbon-like objects of graphite which he regards as vegetable, and names Archczophyton Newberryii? Should these objects prove to be organic, Eozoon will no longer be alone. Besides this the peculiar bodies named Cryptozoum by Hall, and which are intermediate in structure between Eozoon and Loftusia, have now been found as low as the Lower Cambrian. 4 Barrois 1 Notes on Specimens of Eozoon, " Memoirs of Peter Red path Museum," 1888. 2 Bui. Nat. Hist. New Brunswick, No. IX., 1890. 3 Annals N. Y. Academy of Science, 1888. 4 Walcott, Lower Cambrian, 1892. THE DAWN OF LIFE 131 has also recently announced the discovery of forms which he regards as akin to the modern Radiolaria, creatures of a little higher grade than the Foraminifera, in the " Archaean " rocks of Brittany. 1 Thus Eozoon is no longer isolated, but has companions of the same great age with itself. The progress of discovery is also daily carrying the life of the Cambrian to lower beds, and thus nearer to the Laurentian. It is not un- likely that in a few years a pre-Cambrian fauna will force itself on the attention of the most sceptical geologists. REFERENCES: "Life's Dawn on Earth," London, 1875. (Now out of print.) "Specimens of Eozoon Canadense in the Peter Red path Museum, Montreal," 1888. (This memoir contains reference to pre- vious papers.) 1 Natural Science, Oct., 1892. APPENDED NOTES. 1. Stromatopora. It has been usual of late to regard these as allies of the modern Millepores and Hydraetiniae ; but careful study of large series of specimens has convinced me that some species, notably the Stromato- cerium of the Cambro- Silurian and the cryptozoum of the Cambrian, cannot be so referred. I hope to establish this in the future, if time permit. 2. MODERN FORAMINIFERA. The discovery by Brady and Lister of reproductive chamberlets at the margin of the modern orbitolites, tends to connect this with Eozoon. The gigantic foraminiferal species discovered by Agassiz at the Gallipagos, has points of affinity with Eozoon ; and its arenaceous nature does not affect this, as we know sandy species in this group closely allied to others that are calcareous. WHAT MAY BE LEARNED FROM EOZOON. DEDICATED TO THE MEMORY OF DR. WILLIAM B. CARPENTER, WHO, AMONG HIS MANY SERVICES TO SCIENCE, DEVOTED MUCH TlME AND LABOUR TO THE INVESTIGATION OF EOZOON, AND BY HIS KNOWLEDGE OF FORAMINIFERA AND UNRIVALLED POWER OF UNRAVELLING DIFFICULT STRUCTURES DID MUCH TO RENDER IT INTELLIGIBLE. THE MICROSCOPE IN GEOLOGY CONTRIBUTIONS OF THE STUDY OF EOZOON TO OUR KNOWLEDGE OF THE MODE OF PRESERVATION OF FOSSILS ITS TEACHING RELA- TIVELY TO THE ORIGIN OF LIFE AND THE LAWS OF ITS INTRODUCTION AND PROGRESS S. E. 10 SPECIMEN OF EOZOON CANADENSE (DAWSON), showing Genera Form and Osculiform Tubes. (Reproduced from Photograph.) CHAPTER VI. WHAT MAY BE LEARNED FROM EOZOON. THE microscope has long been a recognised and valued aid of the geological observer, and is perhaps now in danger of being somewhat overrated by enthusiastic specialists. To the present writer its use is no novelty. When, as a very young geologist, collecting fossil plants in the coal fields of Novia Scotia, I obtained access to the then recently published work of Witham on the " Internal Structure of Fossil Vege- tables." 1 Fired by the desire to learn something of the structure of the blocks of fossil wood in my collection, I at once procured a microscope of what would now be considered a very im- perfect kind, and proceeded to make attempts to slice and examine my specimens, and was filled with joy when these old blackened stems for the first time revealed to me their wonderful structures. At the same time I extended my studies to every minute form of life that could be obtained from the sea or fresh waters. A few years later (in 1841), when a student in Edinburgh, I made the acquaintance of Mr. Sanderson of that city, who had worked for Nicol and Witham in the preparation of specimens, and learnt the modes which he had employed. Since that time I have been accustomed to subject every rock, earth or fossil which came under my notice to microscopic scrutiny, not as a mere specialist in that mode of observation, or with the parade of methods and details now customary, but with the view of obtaining valuable facts bear- 1 Edinburgh, 1833. 135 136 WHAT MAY BE LEARNED FROM EOZOON ing on any investigation I might have in hand. It was this habit which induced my old friend, Sir William Logan, in 1858 and subsequent years to ask my aid in the study of the forms believed or suspected to be organic, which had been discovered in the course of his surveys of the Laurentian rocks. In one respect this was unfortunate. It occupied much time, inter- fered to some extent with other researches, led to unpleasant controversies. But these evils were more than compensated by the insight which the study gave into the fact of the persistence of organic structures in highly crystalline rocks, and to the modes of ascertaining and profiting by these obscure remains, while it has guided and stimulated enquiry and thought as to the origin and history of life. These benefits entitle the re- searches and discussions on Eozoon to be regarded as marking a salient point in the history of geological discovery, and it is to these principally that I would attract attention in the pre- sent chapter. Perhaps nothing excites more scepticism as to the animal nature of Eozoon than the prejudice existing among geologists that no organism can be preserved in rocks so highly crystalline as those of the Laurentian series. I call this a prejudice, be- eause any one who makes the microscopic structure of rocks and fossils a special study, soon learns that fossils and the rocks containing them may undergo the most remarkable and complete mechanical and chemical changes without losing their minute structure, and that limestones, if once fossiliferous, are hardly ever so much altered as to lose all traces of the organisms which they contained, while it is a most common occurrence to find highly crystalline rocks of this kind abound- ing in fossils preserved as to their minute structure. Let us, however, look at the precise conditions under which this takes place. When calcareous fossils of irregular surface and porous or cellular texture, such as Eozoon may have been, or corals were WHAT MAY BE LEARNED FROM EOZOON 137 and are, become imbedded in clay, marl, or other soft sedi- ment, they can be washed out and recovered in a condition similar to that of recent specimens, except that their pores or cells, if open, may be filled with the material of the matrix, or if not so open that they can be thus filled, they may be more or less incrusted with mineral deposits introduced by water percolating the mass, or may even be completely filled up in this way. But if such fossils are contained in hard rocks, they usually fail, when these are broken, to show their external sur- faces, and, breaking across with the containing rock, they ex- hibit their internal structure merely, and this more or less distinctly, according to the manner in which their cells or cavities have been filled with mineral matter. Here the microscope becomes of essential service, especially when the structures are minute. A fragment of fossil wood which to the naked eye is nothing but a dark stone, or a coral which is merely a piece of grey or coloured marble, or a specimen of common crystalline limestone made up originally of coral frag- ments, presents, when sliced and magnified, the most perfect and beautiful structure. In such cases it will be found that ordinarily the original substance of the fossil remains in a more or less altered state. Wood may be represented by dark lines of coaly matter, or coral by its white or transparent calcareous laminae; while the material which has been introduced, and which fills the cavities, may so differ in colour, transparency, or crystallization, as to act differently on light, and so reveal the original structure. These fillings are very curious. Sometimes they are mere earthy or muddy matter which has been washed into the cavities. Sometimes they are transparent and crystal- line. Often they are stained with oxide of iron or coaly materials. They may consist of carbonate of lime, silica or silicates, sulphate of baryta, oxides of iron, carbonate of iron, iron pyrite, or sulphides of copper or lead, all of which are common materials. They are sometimes so complicated that 133 WHAT MAY BE LEARNED FROM EOZOON I have seen even the minute cells of woody structures, each with several bands of differently coloured materials deposited in succession, like the coats of an onyx agate. A further stage of mineralisation occurs when the substance of the organism is altogether removed and replaced by foreign matter, either little by little, or by being entirely dissolved or decomposed, leaving a cavity to be filled by infiltration. In this state are some silicified woods, and those corals which have been not filled with but replaced by silica, and can thus sometimes be obtained entire and perfect by the solution in an acid of the containing limestone, or by its removal in weathering. In this state are the beautiful silicified corals ob- tained from the corniferous limestone of Lake Erie, which are so perfectly replaced by flinty matter that when weathered out of the limestone, or treated with acid till the latter is removed, we find the coral as perfect as when recent. It may be well to present to the eye these different stages of fossilization. I have attempted to do this in Fig. 13, taking a tabulate coral of the genus Favosites for an example, and supposing the material employed to be calcite and silica. Precisely the same illustra- tion would apply to a piece of wood, except that the cell wall would be carbonaceous matter instead of carbonate of lime. In this figure the dotted parts represent carbonate of lime, the diagonally shaded parts silica or a silicate. Thus we have in the natural state the walls of carbonate of lime and the cavities empty (a). When fossilized the cavities may be merely filled with carbonate of lime, or they may be filled with silica (b, c) ; or the walls themselves may be replaced by silica, and the cavities may remain filled with carbonate of lime (d) ; or both the walls and cavities may be represented by or filled with silica or silicates (e). The ordinary specimens of Eozoon are supposed to be in the third of these stages, though some exist in the second, and I have reason to believe that some have reached to the fifth. I have not met with any in the WHAT MAY BE LEARNED FROM EOZOON 139 fourth stage, though this is not uncommon in Silurian and Devonian fossils. I have further to remark that the reason why wood and the cells of corals so readily become silicified is that the organic matter which they contain, becoming oxidized in decay, produces carbon dioxide, which, by its affinity for alkalies, can decompose soluble silicates and thus throw down their silica in an insoluble state. Thus a fragment of decay- ing wood imbedded in a deposit holding water and alkaline silicates almost necessarily becomes silicified. It is also to be remarked that the ordinary specimens of Eozoon have actually not attained to the extreme degree of mineralization seen in some much more recent silicified woods and corals, inasmuch a UJ iin f! FIG. 13. Diagram showing different States of Fossilization of a cell of a Tubulate Coral, (a) Natural condition walls calcite, cell empty, (b) Walls calcite, celt filled with the same, (c) Walls calcite, cell filled with silica or silicate, (d) Walls silicified, cell filled with calcite. (. Oweni) and other forms belonging to the group of Microsauria of which Hylonomus is the type. A second species of that genus (H. Wymani) has already been mentioned. A similar creature, but of larger size and with teeth of a wedge or chisel shape, has been referred to a distinct genus, Smikrpeton. It seems to have been rare, and the only skeleton found is very imperfect. Dolichosoma longissimum, a serpentiform Permian Balrachian after Fritsch. This and Hylonomus are opposite or extreme types in regard to general form. THE OLDEST AIR-BREATHERS 287 Its teeth are of a form that may have served even for vegetable food, as their sharp edges must have had considerable cutting power. Another curious form of tooth appears in the genus Hylerpeton. It has the points worked into oblique grooves separated by sharp edges, which must have greatly aided in piercing tough integument. These creatures seem to have been of stout and robust build, with large limbs. Still another generic type (Fritschid) is represented by a species near to Hylonomus in several respects, and with long and beau- tifully formed limb bones, but with the belly protected with rod-like bodies instead of scales. In this respect Hylerpeton is somewhat intermediate, having long and narrow scales on the belly instead of the oval or roundish scales of Hylonomus. All these last-mentioned forms are Microsaurians, with simple teeth and well-developed ribs and limbs, and smooth cranial bones. Two other species are represented by portions of single skeletons too imperfect to allow them to be certainly determined. I would emphasize here that the vertebrate animals found in the erect trees are necessarily a selection from the most exclusively terrestrial forms, and from the smaller species of these. The numerous newt-like and serpentiform species found in the shales of the coal formation could not find access to these peculiar repositories, nor could the larger species of the Laby- rinthodonts and their allies, even if they were in the habit of occasionally prowling in the forests in search of prey, and this would scarcely be likely, more especially as the waters must have afforded to them much more abundant supplies of food. Of the numerous species figured by Fritsch, Cope and Huxley, only a few approach very near to the forms entrapped in the old hollow Sigillariae, though several have characters half ba- trachian and half reptilian. 288 THE OLDEST AIR-BREATHERS INVERTEBRATE AIR-BREATHERS. The coal formation rocks have afforded Land Snails, Milli- pedes, Spiders, Scorpions and Insects, so that all the great types of invertebrate life which up to this day can live on land already had representatives in this ancient period. Some of them, indeed, we can trace further back, the land snails prob- ably to the Devonian, the Millipedes to the same period, and the Scorpions and insects as far as the Silurian. No land ver- tebrate is yet known, older than the Lower Carboniferous, but there is nothing known to us in physical condition, to preclude the existence of such creatures at least in the Devonian. It would take us too far afield to attempt to notice the in- vertebrate land life of the Palaeozoic in general. This has been done in great detail by Dr. Scudder. I shall here limit myself to the animals found in our erect trees, and merely touch in- cidentally on such others as may be connected with them. I have already mentioned the occurrence of a land snail, a true pulmonate mollusk, in the first find by Lyell and my- self at Coal Mine Point, and this was the first animal of this kind known in any rocks older than the Purbeck formation of England. It is one of the groups of so-called Chrysalis-shells, scarcely distinguishable at first sight from some modern West Indian species, and distinctly referable to the modern genus Pupa. It was named Pupa vetusta, and a second and smaller species subsequently found was named P. Bigsbyi^ and a third of different form, and resembling the modern snails, bears the name Zonites priscus. The only other Palaeozoic land mol- lusks known at present are a few species found in the coal formation of Ohio, and a fragment supposed to indicate another species from the Devonian plant beds of St. John's, New Brunswick. This last is the oldest known evidence of pulmon- ate snails. If we ask the precise relations of these creatures to modern snails, it may be answered that of the two leading sub- S. E. 2 I CARBONIFEROUS LAND SNAILS. Pufa vettista, Darwin, and Conuhts prisca, Carpenter, with egg of Pupa vetnstatt\z whole considerably magnified. I published in 1880, in the Ameri- can Journal of Science, a fragment of what seemed to be a land snail, from the Middle Erian plant beds of St. John, New Brunswick (Strophia grand- ova, figured above), but have mentioned it with some doubt in the text. Mr. G. F. Matthew has, however, recently communicated to the Royal Society of Canada a second species, found by Mr. W. I. \Vilson in the same beds, and which he names Pupa primava. It is accompanied with a scorpion and a millipede. Thus the existence of Land Snails of the Pupa type in the Devonian may be considered as established, A DEVONIAN LAND SNAIL, THE OLDEST AIR-BREATHERS 289 divisions of the group of air-breathing snails (Pulmonifera), the Operculate, or those with a movable plate to close the mouth of the shell, and the Inoperculate, or those that are destitute of any such shelly lid or operculum to close the shell, the first has been traced no farther back than the Eocene. The second or inoperculate division, includes some genera that are aquatic and some that are terrestrial. Of the aquatic genera no re- presentatives are known in formations older than the Wealden and Purbeck, and these only in Europe. The terrestrial group, or the family of the Heliddc^^ which, singularly enough, is that which diverges farthest from the ordinary gill-bearing Gastero- pods, is the one which has been traced farthest back, and includes the Palaeozoic species. It is further remarkable that a very great gap exists in the geological history of this family. No species are known between the Carboniferous and the early Tertiary, though in the intervening formations there are many fresh-water and estuarine deposits in which such remains might be expected to occur. There is perhaps no reason to doubt the continuance of the Helicidae through this long por- tion of geological time, though it is probable that during the interval the family did not increase much in the numbers of its species, more especially as it seems certain that it has its culmination in the modern period, where it is represented by very many and large species, which are dispersed over nearly all parts of our continents. The mode of occurrence of the Palaeozoic Pulmonifera in the few localities where they have been found is characteristic. The earliest known species, Pupa vetttsta, was found, as already stated, in the material filling the once hollow stem of a Sigillaria at the South Joggins in Nova Scotia, and many additional specimens have subsequently been obtained from similar repositories in the same locality, where they are associ- ated with bones of Batrachians and remains of Millipedes. Other specimens, and also the species Zonites priscus^ have 290 THE OLDEST AIR-BREATHERS been found in a thin, shaly layer, containing debris of plants and crusts of Cyprids, and which was probably deposited at the outlet of a small stream flowing through the coal-formation forest. The two species found in Illinois occur, according to Bradley, in an underclay or fossil soil which may have been the bed of a pond or estuary, and subsequently became a forest subsoil. The Erian species occurs in shales charged with remains of land plants, and which must consequently have received abundant drainage from neighbouring land. It is only in such deposits that remains of true land snails can be expected to occur ; though, had fresh water or brackish water Pulmonates abounded in the Carboniferous age, their remains should have occurred in those bituminous and calcareo-bitu- minous shales which contain such vast quantities of debris of Cyprids, Lamellibranchs and fishes of the period, mixed with fossil plants. The specimen first obtained in 1887 having been taken by Sir Charles Lyell to the United States, and submitted to the late Prof. Jeffries Wyman, the shell in question was recognised by him and the late Dr. Gould, of Boston, as a land shell. It was subsequently examined by M. Deshayes and Mr. Gwyn Jeffries, who concurred in this determination ; and its micro- scopic structure was described by the late Prof. Quekett, of London, as similar to that of modern land shells. The single specimen obtained on this occasion was somewhat crushed, and did not show the aperture. Hence the hesitation as to its nature, and the delay in naming it, though it was figured and described in the paper above cited in 1852. Better specimens showing the aperture were afterward obtained by the writer, and it was named and described by him in his "Air-breathers of the Coal Period," in 1863. Owen, in his "Palaeontology," subsequently proposed the generic name Dendropupa. This I have hesitated to accept, as expressing a generic distinction not warranted by the facts ; but should THE OLDEST AIR-BREATHERS 29 1 the shell be considered to require a generic or sub-generic distinction, Owen's name should be adopted for it. There seems, however, nothing to prevent it from being placed in one of the modern sub-genera of simple-lipped Pupae. With regard to the form of its aperture, I may explain that some currency has been given to an incorrect representation of it, through defective specimens. In the case of delicate shells like this, imbedded in a hard matrix, it is of course difficult to work out the aperture perfectly ; and in my published figure in the "Air-breathers," I had to restore somewhat the broken specimens in my possession. This restoration, speci- mens subsequently found have shown to be very exact. As already stated, this shell seems closely allied to some modern Pupae. Perhaps the modern species which approaches most nearly to it in form, markings and size, is Macrocheilus Gossei from the West Indies, specimens of which were sent to me some years ago by Mr. Bland, of New York, with the remark that they must be very near to my Carboniferous species. Such edentulous species as Pupa (Leucochtla} fallax of Eastern America very closely resemble it ; and it was re- garded by the late Dr. Carpenter as probably a near ally of those species which are placed by some European concholo- gists in the genus Pupilla. Pupa vetusta has been found at three distinct levels in the coal formation of the South Joggins. The lowest is the shale above referred to. The next, 1,217 f eet higher, is that of the original discovery. The third, 800 feet higher, is in an erect Sigillaria holding no other remains. Thus, this shell has lived in the locality at least during the accumulation of 2,000 feet of beds, including a number of coals and erect forests, as well as beds of bituminous shales and calcareo-bituminous shale, the growth of which must have been very slow. In the lowest of these three horizons the shells are found, as already stated, in a thin bed of concretionary clay of dark 2Q2 THE OLDEST AIR-BREATHERS grey colour, though associated with reddish beds. It contains Zonitcs priscus as well, though this is very rare, and there are a few valves of Cythere and shells of Naiadites as well as carbonaceous fragments, fronds of ferns, Trigonocarpa^ etc. The Pupa are mostly adult, but many very young shells also occur, as well as fragments of broken shells. The bed -is evidently a layer of mud deposited in a pond or creek, or at the mouth of a small stream. In modern swamps multitudes of fresh-water shells occur in such places, and it is remarkable that in this case the only Gasteropods are land shells, and these very plentiful, though only in one bed about an inch in thickness. This would seem to imply an absence of fresh- water Pulmonifera. In the erect Sigillaria of the second horizon the shells occur either in a sandy matrix, more or less darkened with vegetable matter, or in a carbonaceous mass composed mainly of vegetable debris. Except when crushed or flattened, the shells in these repositories are usually filled with brownish calcite. From this I infer that most of them were alive when imbedded, or at least that they contained the bodies of the animals ; and it is not improbable that they sheltered themselves in the hollow trees, as is the habit of many similar animals in modern forests. Their residence in these trees, as well as the characters of their embryology, are illustrated by the occurrence of their mature ova. One of those, which I have considered worth figuring, has been broken in such a way as to show the embryo shell. They may also have formed part of the food of the reptilian animals whose remains occur with them. In illustration of this I have elsewhere stated that I have found as many as eleven unbroken shells of Physa heterostropha in the stomach of a modern Menobranchus. I think it certain, however, that both the shells and the reptiles occurring in these trees must have been strictly terrestrial in their habits, as they could not have found admission to the erect trees unless the ground had THE OLDEST AIR-BREATHERS 293 been sufficiently dry to allow several feet of the imbedded hollow trunks to be free from water. In the highest of the three horizons the shells occurred in an erect tree, but without any other fossils, and they had apparently been washed in along with a greyish mud. 1 If we exclude the alleged Palceorbis referred to below, all the Palaeozoic Pulmonifera hitherto found are American. Since, however, in the Carboniferous age, Batrachians, Arach- nidans, Insects and Millipedes occur on both continents, it is not unlikely that ere long European species of land snails will be announced. The species hitherto found in Eastern America are in every way strangely isolated. In the plant beds of St. John, about 9,000 feet in thickness, and in the coal formation of the South Joggins, more than 7,000 feet in thickness, no other Gasteropods occur, nor, I believe, do any occur in the beds holding land snails in Illinois. Nor, as already stated, are any of the aquatic Pulmonifera known in the Palaeozoic. Thus, in so far as at present known, these Palaeozoic snails are separated not only from any predecessors, if there were any, or successors, but from any contemporary animals allied to them. It is probable that the land snails of the Erian and Carboni- ferous were neither numerous nor important members of the faunae of those periods. Had other species existed in any considerable numbers, there is no reason why they should not have been found in the erect trees, or in those shales which contain land plants. More especially would the discovery of any larger species, had they existed, been likely to have occurred. Further, what we know of the vegetation of the Palaeozoic period would lead us to infer that it did not abound 1 The discovery of the shells in this tree was made by Albert I. Hill, C.E. The tree is in Group XXVI. of Division 4 of my Joggins section. The original reptiliferous trees are in Group XV., and the lowest bed in Group VIII. 294 THE OLDEST AIR-BREATHERS in those succulent and nutritious leaves and fruits which are most congenial to land snails. It is to be observed, however, that we know little as yet of the upland life of the Erian or Carboniferous. The animal life of the drier parts of the low country is indeed as yet very little known ; and but for the revelations in this respect of the erect trees in one bed in the coal formation of Nova Scotia, our knowledge of the land snails and Millipedes, and also of an eminently terrestrial group of reptiles, the Microsauria, would have been much more imperfect than it is. We may hope for still further revelations of this kind, and in the meantime it would be premature to speculate as to the affinities of our little group of land snails with animals either their contemporaries or belonging to earlier or later formations, except to note the fact of the little change of form or structure in this type of life in that vast interval of time which separates the Erian period from the present day. It. may be proper to mention here the alleged -Pulmonifera of the genus Palceorbis described by some German naturalists. These I believe to be worm tubes of the genus Spirorbis, and in fact to be nothing else than the common S. carbonarius or S. pusillus of the coal formation. The history of this error may be stated thus. The eminent palaeobotanists Germar, Gceppert and Geinitz have referred the Spirorbis, so common in the Coal measures to the fungi, under the name Gyromyces, and in this they have been followed by other naturalists, though as long ago as 1868 I had shown that this little organism is not only a calcareous shell, attached by one side to, vegetable inatters and shells of mollusks, but that it has the microscopic structure characteristic of modern shells of this type. 1 More recently Van Beneden, Caenius, and Goldenberg, perceiving that the fossil is really a calcareous shell, but 1 "Acadian Geology," 2nd edition, p. 205. CARBONIFEROUS MILLIPEDES, Xylobius Sigillarice, Darwin (a, r), and Archiuhts xylobioides, Scudder (b}. CARBONIFEROUS COCKROACH. Blaltina Bretonensis, Sc. CARBONIFEROUS SCORPION. Anthracomartus Carbonarius, abdominal segments. THE OLDEST AIR-BREATHERS 295 apparently unaware of the observations made in this country by myself and Mr. Lesquereux, have held the Spirorbis to be a pulmonate mollusk allied to Planorbis^ and have supposed that its presence on fossil plants is confirmatory of this view, though the shells are attached by a flattened side to these plants, and are also found attached to shells of bivalves of the genus Naiadites. Mr. R. Etheridge, jun., of the Geological Survey of Great Britain, has summed up the evidence as to the true nature of these probably brackish-water shells, and has revised and added to the species, in a series of articles in the Geological Magazine of London, vol. viii. The erect trees of Coal Mine Point are rich in remains of Millipedes. The first of these (Xylobius Sigillaria), which was the first known Palaeozoic Myriapod, was described by me from specimens found in a tree extracted in 1852, and this, with a number of other remains subsequently found, was after- wards placed in the hands of Dr. Scudder, who has recognised in the material submitted to him eight species belonging to three genera (Xylobius^ Archmlus^ and Amynifyspts). These animals in all probability haunted these trees to feed on the decaying wood and other vegetable matter, and were un- doubtedly themselves the prey of the Microsaurians. Though these were the earliest known, their discovery was followed by that of many other species in Europe and America, and some of them as old as the Devonian. 1 The only other remains of Air-breathers found in the erect trees belong to Scorpions, of which some fragments remain in such a state as to make it probable that they have been partially devoured by the imprisoned reptiles. No remains of any aquatic animals have been found in these trees. The 1 The two first-named genera from the erect trees, according to Scudder, belong to an extinct family of Millipedes, which he names Archiulidoe, and places with other Carboniferous genera in the order Archipolypodj. The third belongs to family Euphoberidse. Proc. R. S. of London, 1892. 296 THE OLDEST AIR-BREATHERS Scorpions are referred by Scudder to three species belonging to two genera. 1 In the previous paper we have considered the mode of accumulation of Coal, and it may be useful here to note the light thrown on this subject by the Air-breathers of the coal formation and their mode of occurrence. In no part of the world are the coal measures better developed, or more fully exposed, than in the coast sections of Nova Scotia and Cape Breton ; and in these, throughout their whole thickness, no indication has been found of any of the marine fossils of the Lower Carboniferous Limestone. Abun- dant remains of fishes occur, but these may have frequented estuaries, streams and ponds, and the greater part of them are small ganoids which, like the modern Lepidosteus and Amia, may have been specially fitted by their semi-reptilian respira- tion, for the impure waters of swampy districts. Bivalve mollusks also abound ; but these are all of the kinds to which I have given the generic name Naiadites, and Mr. Salter those of Anthracomya and Anthracoptera. These shells are all distinct from any known in the marine limestones. Their thin edentulous valves, their structure consisting of a wrinkled epidermis, a thin layer of prismatic shell and an inner layer of imperfectly pearly shell, all remind us of the Anodons and Unios. A slight notch in front concurs with their mode of occurrence in rendering it probable that, like mussels in modern estuaries, they attached themselves to floating or sunken timber. They are thus removed, both in structure and habit, from truly marine species ; and may have been fresh- water or brackish-water mussels closely allied to modern Unios. The crustaceans (Eurypterus, Diplostylus, Cyprids], and the 1 Mazonia Acadica, and a second species of Mazonia, with fragments of a third species, generally distinct. Proceedings Royal Society of London, THE OLDEST AIR-BREATHERS 297 worm shell (Spirorbis) found with them, are not necessarily marine, though some of them belonged probably to brackish water, and they have not yet been found in those carboniferous beds deposited in the open sea. There is thus in the whole thickness of the middle coal measures of Nova Scotia a remarkable absence at least of open sea animals ; and if, as is quite probable, the sea inundated at intervals the areas of coal accumulation, the waters must have been shallow, and to a great extent land-locked, so that brackish-water rather than marine animals inhabited them. On the other hand, there are in these coal measures abundant evidences of land surfaces ; and subaerial decay of vegetable matter in large quantity is proved by the occurrence of the mineral charcoal of the coal itself, as I have elsewhere shown. 1 The erect trees which occur at so many levels also imply subaerial decay. A tree imbedded in sediment and remaining under water, could not decay so as to become hollow and deposit the remains of its wood in the state of mineral charcoal within the hollow bark. Yet this is the case with the greater part of the erect Sigillariae which occur at more than twenty levels in the Joggins section. Nor could such hollow trunks become repositories for millipedes, snails and reptiles, if under water. On the other hand, if, as seems necessary to explain the character of the reptiliferous erect trees, these remained dry, or nearly so, in the interior, this would imply not merely a soil out of water, but comparatively well drained ; as would indeed always be the case, when a flat resting on a sandy subsoil was raised several feet above the level of the water. Further, though the peculiar character of the roots of Sigillarm and Calamites may lend some counten- ance to the supposition that they could grow under water, or in water-soaked soils, this will not apply to coniferous trees, to 1 Journal of Geological Survey ', vol. xv. 298 THE OLDEST AIR-BREATHERS ferns, and other plants, which are found under circumstances which show that they grew with the Sigillarice. In the coal measures of Nova Scotia, therefore, while marine conditions are absent, there are ample evidences of fresh-water or brackish-water conditions, and of land surfaces, suitable for the air-breathing animals of the period. Nor do I believe that the coal measures of Nova Scotia were exceptional in this respect. It is true that in Great Britain evidences of marine life do occur in the coal measures ; but not, so far as I am aware, in circumstances which justify the inference that the coal is of marine origin. Alternations of marine and land remains, and even mixtures of these, are frequent in modern submarine forests. When we find, as at Fort Lawrence in Nova Scotia, a modern forest rooted in upland soil forty feet below high-water mark, 1 and covered with mud containing living Tellinas and Myas, we are not justified in inferring that this forest grew in the sea. We rather infer that subsidence has occurred. In modern salt marshes it is not unusual to find every little runnel or pool full of marine shell fish, while in the higher parts of the marsh land plants are growing ; and in. such places the deposit formed must contain a mixture of land plants and marine animals with salt grasses and herbage the whole in situ? These considerations serve, I think, to explain all the apparently anomalous associations of coal plants with marine fossils ; and I do not know any other arguments of apparent weight that can be adduced in favour of the marine or even 1 Journal of Geological Society, vol. xi. 2 In the marshes at the mouth of Scarborough River, in Maine, channels not more than a foot wide, and far from the sea, are full of Mussels and Myae; and in little pools communicating with these channels there are often many young Limuli, which seem to prefer such places, and the cast- off shells and other remains of which may become imbedded in mud and mixed with land plants, just as in the shales of the coal measures. THE OLDEST AIR-BREATHERS 299 aquatic origin of coal, except such as are based on misconcep- tions of the structure and mode of growth of sigillaroid trees and of the stratigraphical relations of the coal itself. 1 It is to be observed, however, that while I must maintain the essen- tially terrestrial character of the ordinary coal and of its plants, I have elsewhere admitted that cannel coals and earthy bitumen present evidences of subaquatic deposition ; and have also abundantly illustrated the facts that the coal plants grew on swampy flats, liable not only to river inundations, but also to subsidence and submergence. 2 In the oscillation of these conditions it is evident that Sigillarice and their con- temporaries must often have been placed in conditions un- favourable or fatal to them, and when their remains are preserved to us in these conditions, we may form very incorrect inferences as to their mode of life. Further, it is to be observed that the conditions of submergence and silting up which were favourable to the preservation of specimens of Sigillarice as fossils, must have been precisely those which 1 It is unfortunate that few writers on this subject have combined with the knowledge of the geological features of the coal a sufficient acquaint- ance with the phenomena of modern marshes and swamps, and with the conditions necessary for the growth of plants such as those of the coal. It would be easy to show, were this a proper place to do so, that the " swells," " rock faults," splitting of beds, and other appearances of coal seams quite accord with the theory of swamp accumulation ; that the plants associated with Sigillaritz could not have lived with their roots immersed in salt water ; that the chemical character of the underclays implies drainage and other conditions impossible under the sea ; that the composition and minute structure of the coal are incompatible with the supposition that it is a deposit from water, and especially from salt water; and that it would be more natural to invoke wind driftage as a mode of accumulation for some of the sandstones, than water driftage for the forma- tion of the coal. At the same time it is pretty certain that such beds as the cannels and earthy bitumens which appear to consist of finely com- minuted vegetable matter, without mineral charcoal, may have been de- posits of muck in shallow lakes or lagoons. 2 Journal of Geol, Socy., vols. x. and xv., and "Acadian Geology." 30O THE OLDEST AIR-BREATHERS were destructive to them as living plants ; and on the contrary, that the conditions in which these forests may have flourished for centuries must have been those in which there was little chance of their remains being preserved to us, in any other condition at least than that of coal, whih reveals only to careful microscopic examination the circumstances, whether aerial or aquatic, under which it was formed. It is also noticeable that, in conditions such as those of the coal formation, it would be likely that some plants would be specially adapted to occupy newly emerged flats and places liable to inundation and silting up. I believe that many of the SigillaricE) and still more eminently the Calamites^ were suit- able to such stations. There is direct evidence that the nuts named Trigonocarpa were drifted extensively by water over submerged flats of mud. Many Cardiocarpa were winged seeds which may have drifted in the air. The Calamites may, like modern Equiseta^ have produced spores with elaters cap- able of floating them in the wind. One of the thinner coals at the Joggins is filled with spores or spore cases that seem to have carried hairs on their surfaces, and may have been suited to such a mode of dissemination. I have elsewhere proved l that at least some species of Calamites were, by their mode of growth, admirably fitted for growing amid accumulating sedi- ment, and for promoting its accumulation. The reptiles of the coal formation are probably the oldest known to us, and possibly, though this we cannot affirm, the highest products of creation in this period. Supposing, for the moment, that they are the highest animals of their time, and, what is perhaps less likely, that those which we know are a fair average of the rest, we have the curious fact that they are all carnivorous, and the greater part of them fitted to find food in the water as well as on the land. The plant feeders of the period, on the land at least, are all invertebrates, as snails, 1 "Acadian Geology," chapter on Coal Plants, THE OLDEST AIR-BREATHERS 30! millipedes, and perhaps insects. The air-breathing vertebrates are not intended to consume the exuberant vegetable growth, but to check the increase of its animal enemies. Plant life would thus seem to have had in every way the advantage. The millipedes probably fed only on roots and decaying sub- stances, the snails on the more juicy and succulent plants growing in the shadow of the woods, and the great predomi- nance of the family of cockroaches among carboniferous insects points to similar conclusions as to that class. While, moreover, the vegetation of the coal swamps was most abundant, it was not, on the whole, of a character to lead us to suppose that it supported many animals. Our knowledge of the flora of the coal swamps is sufficiently complete to exclude from them any abundance of the higher phaenogamous plants. We know little, it is true, of the flora of the uplands of the period ; but when we speak of the coal-formation land, it is to the flats only that we refer. The foliage of the plants on these flats with the exception of that of the ferns, was harsh and meagre, and there seem to have been no grasses or other nutritious herbaceous plants. These are wants of themselves likely to exclude many of the higher forms of herbivorous life. On the other hand, there was a profusion of large nut-like seeds, which in a modern forest would probably have afforded subsistence to squirrels and similar animals. The pith and thick soft bark of many of the trees must at certain seasons have contained much nutri- tive matter, while there was certainly sufficient material for all those insects whose larvae feed on living and dead timber, as well as for the creatures that in turn prey on them. It is re- markable that there seem to have been no vertebrate animals fitted to avail themselves of these vast stores of food. The question : " What may have fed on all this vegetation ? " was never absent from my mind in all my explorations of the Nova Scotia coal sections ; but no trace of any creature other than those already mentioned has ever rewarded my search. In s. E. 22 302 THE OLDEST AIR-BREATHERS Nova Scotia it would seem that a few snails, gally-worms, and insects were the sole links of connection between the plant creation and air-breathing vertebrates. Is this due to the paucity of the fauna, or the imperfection of the record ? The fact that a few erect stumps have revealed nearly all the air- breathers yet found, argues strongly for the latter cause ; but there are some facts bearing on the other side. A gally-worm, if, like its modern relatives, hiding in crevices of wood in forests, was one of the least likely animals to be found in aqueous deposits. The erect trees gave it its almost sole chance of preservation. Pupa vetusta is a small species, and its shell very thin and fragile, while it probably lived among thick vegetation. Further, the measures 2,000 feet thick, separating the lowest and highest beds in which it occurs, in- clude twenty-one coal seams, having an aggregate thickness of about twenty feet, three beds of bituminous limestone of animal origin, and perhaps twenty beds holding Stigmaria in situ, or erect Sigillarice and Catamites. The lapse of time implied by this succession of beds, many of them necessarily of very slow deposition, must be very great, though it would be mere guess work to attempt to resolve it into years. Yet long though this interval must have been, Pupa vetusta lasted without one iota of change through it all ; and, more remarkable still, was not accompanied by more than two other species of its family. Where so many specimens occur, and in situations so diverse, without any additional species, the inference is strong that no other of similar habits existed. If in any of those subtropical islands, whose climate and productions somewhat resemble those of the coal period, after searching in and about decaying trees, and also on the bars upon which rivers and lakes drifted their burdens of shells, we should find only three species, but one of these in very great numbers, we would surely conclude that other species, if present, were very rare. Again, footprints referable to Dendrerpeton, or similar animals, THE OLDEST AIR-BREATHERS 303 occur in the loWer Carboniferous beds below the marine lime- stones, in the middle coal measures, and in the upper coal formation, separated by a thickness of beds which may be estimated at 15,000 feet, and certainly representing a vast lapse of time. Did we know the creature by these impressions alone, we might infer its continued existence for all this great length of time ; but when we also find its bones in the princi- pal repositories of reptile remains, and in company with the other creatures found with it, we satisfy ourselves that of them all it was the most likely to have left its trail in the mud flats. We thus have reason to conclude that it existed alone during this period, in so far as its especial kind of habitat was con- cerned ; though there lived with it other reptiles, some of which, haunting principally the woods, and others the water, were less likely to leave impressions of their footprints. These may be but slight indications of truth, but they convey strong impressions of the persistence of species, and also of the pau- city of species belonging to these tribes at the time. If we could affirm that the Air-breathers of the coal period were really the first species of their families, they might acquire additional interest by their bearing on this question of origin of species. We cannot affirm this ; but it may be a harmless and not uninstructive play of fancy to suppose for a moment that they actually are so, and to inquire on this supposition as to the mode of their introduction. Looking at them from this point of view, we shall first be struck with the fact that they belong to all of the three great leading types of animals which include our modern Air-breathers the Vertebrates, the Arthro- pods, and the Mollusks. We have besides to consider in this connection that the breathing organs of an insect are air tubes opening laterally (tracheae), those of a land snail merely a modification of the chamber which in marine species holds the gills, while those of the reptiles represent the air bladder of the fishes. Thus, in the three groups the breathing organs are 304 THE OLDEST AIR-BREATHERS quite distinct in their nature and affinities. This at once ex- cludes the supposition that they can all have been derived from each other within the limits of the coal period. No transmu- tationist can have the hardihood to assert the convertibility, by any direct method, of a snail into a millipede or an insect, or of either into a reptile. The plan of structure in these crea- tures is not only different, but contrasted in its most essential features. It would be far more natural to suppose that these animals sprang from aquatic species of their respective types. We should then seek for the ancestors of the snail in aquatic Gasteropods, for those of the millipede in worms or Crustaceans, and for those of the reptiles in the fishes of the period. It would be easy to build up an imaginary series of stages, on the principle of natural selection, whereby these results might be effected ; but the hypothesis would be destitute of any sup- port from fact, and would be beset by more difficulties than it removes. Why should the result of the transformation of water snails breathing by gills be a Pupa ? Would it not much more likely be an Auricula or a Limnea ? It will not solve this difficulty to say that the intermediate forms became ex- tinct, and so are lost. On the contrary, they exist to this day, though they were not, in so far as we know, introduced so early. But negative evidence must not be relied on; the record is very imperfect, and such creatures may have existed, though unknown to us. It may be answered that they could riot have existed in any considerable numbers, else some of their shells would have appeared in the coal-formation beds, so rich in crustaceans and bivalve mollusks. Further, the little Pupa remained unchanged during a very long time, and shows no tendency to resolve itself into anything higher, or to descend to anything lower, while in the lowest bed in which it occurs it is associated with a round snail of quite different type. Here, if anywhere, in what appears to be the first introduction of air-breathing invertebrates, we should be able to find the THE OLDEST AIR-BREATHERS 305 evidences of transition from the gills of the Prosobranchiate and the Crustacean to the air sac of the Pulmonate and the tracheae of the millipede. It is also to be observed that many other structural changes are involved, the aggregate of which makes a Pulmonate or a millipede different in every particular from its nearest allies among gill-bearing Gasteropods or Crustaceans. It may be said, however, that the links of connection be- tween the coal reptiles and fishes are better established. All the known coal reptiles have leanings to the fishes in certain characters ; and in some, as in Archegosaurus, these are very close. Still the interval to be bridged over is wide, and the differences are by no means those which we should expect. Were the problem given to convert a ganoid fish into an Archegosaurus or Dendrerpeton, we should be disposed to retain unchanged such characters as would be suited to the new habits of the creature, and to change only those directly related to the objects in view. We should probably give little attention to differences in the arrangement of skull bones, in the parts of the vertebrae, in the external clothing, in the micro- scopic structure of the bone, and other peculiarities for serving similar purposes by organs on a different plan, which are so conspicuous so soon as we pass from the fish to the Batrachian. It is not, in short, an improvement of the organs of the fish that we witness so much as the introduction of new organs. 1 The foot of the batrachian bears, perhaps, as close a relation to the fin of the fish as the screw of one steamship to the paddle wheel of another, or as the latter to a carriage wheel ; and can be just as rationally supposed to be not a new instrument, but the old one changed. In this connection even a footprint in the sand startles us as much as that of Friday did Robinson 1 An ingenious attempt by Prof. Cope, to deduce the batrachian foot from the fins of certain carboniferous fishes, will be found in the Proceed- ings of the Philos, Academy of Philadelphia for the present year. 306 THE OLDEST AIR-BREATHERS Crusoe. We see five fingers and toes, and ask how this numerical arrangement started at once from fin rays of fishes all over the world ; and how it has continued unchanged till now, when it forms the basis of our decimal arithmetic. Again, our reptiles of the coal do not constitute a continuous series, and belong to a great number of distinct genera and families, nor is it possible that they can all, except at widely different times, have originated from the same source. It either happened, for some unknown reason, that many kinds of fishes put on the reptilian guise in the same period, or else the vast lapse of ages required for the production of a reptile from a fish must be indefinitely increased for the production of many dissimilar reptiles from each other ; or, on the other hand, we must suppose that the limit between the fish and reptile being once overpassed, a facility for comparatively rapid changes became the property of the latter. Either supposition would, I think, contradict such facts bearing on the subject as are known to us. We commenced with supposing that the reptiles of the Coal might possibly be the first of their family, but it is evident from the above considerations, that on the doctrine of natural selection, the number and variety of reptiles in this period would imply that their predecessors in this form must have existed from a time as early as any in which even fishes are known to exist ; so that if we adopt any hypothesis of deriva- tion, it would probably be necessary to have recourse to that which supposes at particular periods a sudden and as yet un- accountable transmutation of one form into another ; a view which, in its remoteness from anything included under ordinary natural laws, does not materially differ from that currently re- ceived idea of creative intervention, with which, in so far as our coal reptiles can inform us, we are for the present satisfied. There is one other point which strikes the naturalist in con- sidering these animals, and which has a certain bearing on such THE OLDEST AIR-BREATHERS 307 hypothesis. It is the combination of various grades of reptilian types in these ancient creatures. It has been well remarked by Hugh Miller, and more fully by Agassiz, that this is charac- teristic of the first appearance of new groups of animals. Now selection, as it acts in the hands of the breeder, tends to specialization ; and natural selection, if there is such a thing, is supposed to tend in the same direction. But when some dis- tinctly new form is to be introduced, an opposite tendency seems to prevail, a sort of aggregation in one species of char- acters afterward to be separated and manifested in distinct groups of creatures. The introduction of such new types also tends to degrade and deprive of their higher properties pre- viously existing groups of lower rank. It is easy to perceive in all this, law and order, in that higher sense in which these terms express the will and plan of the Supreme Mind, but not in that lower sense in which they represent the insensate operation of blind natural forces. REFERENCES : " Air-breathers of the Coal Period." Montreal, 1886. Papers on Reptiles, etc., in South Joggins Coal Field, Journal oj Geological Society of London, vols. ix. x. xi. xvi. Remains of Ani- mals in Erect Trees in the Coal Formation of Nova Scotia, Trans. Royal Society, 1881. "Acadian Geology," fourth edition, 1891. Re- vision of Land Snails of the Palaeozoic Era, Am. Journal of Science, vol. xx., 1880. Supplementary Report to Royal Society of London, Proceedings, 1892. Notice of additional Reptilian Remains, Geo- logical Magazine of London, 1 89 1 . MARKINGS, FOOTPRINTS AND FUCOIDS. DEDICATED TO THE MEMORY OF THE LATE DR. J. J. BIGSBY, F.R.S., OF LONDON, THE PAINSTAKING AND ACCURATE AUTHOR OF THE THESAURUS SILURICUS AND DEVONICO-CARBONIFERUS, A WARM AND KIND FRIEND AND CHRISTIAN GENTLEMAN AND ONE OF THE PIONEERS OF CANADIAN GEOLOGY. REMINISCENCES OF LYELL'S WORK TIDAL FLATS OF THE BAY OF FUNDY RILL MARKS AND SHRINKAGE CRACKS WORM TRAILS AND BURROWS THE PACES OF LIMU- LUS FUCOIDS VERSUS TRAILS FOOTPRINTS OF VER- TEBRATES TRACK OF LIMULUS. Modern, Orchard Beach. Showing its resemblance to the Protechnites of the Cambrian. (Page 320.) CHAPTER XL MARKINGS, FOOTPRINTS AND FUCOIDS. I BELIEVE my attention was first directed to the markings made by animals on the surfaces of rocks, when travelling with the late Sir Charles Lyell in Nova Scotia, in 1842. He noticed with the greatest interest the trails of worms, insects, and various other creatures, and the footprints of birds on the surface of the soft red tidal mud of the Bay of Fundy, and subsequently published his notes on the various markings in these deposits in his "Travels in North America," and in a paper presented to the Geological Society of London. I well re- member how, in walking along the edge of the muddy shore, he stopped to watch the efforts of a grasshopper that had leaped into the soft ooze, and was painfully making a most complicated trail in his effort to escape. Sir Charles re- marked that if it had been so fortunate as to make these strange and complicated tracks on some old formation now hardened into stone and buried in the earth, it might have given occasion to much learned discussion. At a later period I found myself perplexed in the study of fossil plants by the evident errors of many palaeobotanists un- acquainted with modern markings on shores, in referring all kinds of mere markings to the vegetable kingdom, and espe- cially to the group of fucoids or seaweeds, which had become a refuge for destitute objects not referable to other kinds of fossils. It thus became necessary to collect and study these objects, as they existed in rocks of different ages, and to com- 312 MARKINGS, FOOTPRINTS AND FUCOIDS pare them with the examples afforded by the modern beach ; and perhaps no locality could have afforded better opportuni- ties for this than the immense tidal flats of the finest mud left bare by the great tides of the Bay of Fundy in Nova Scotia. At a more recent period still, the subject has come into great prominence in Europe, and if we are to gauge its importance by the magnitude of the costly illustrated works devoted to it by Delgado, Saporta, Nathorst, and others, and the multitude of scattered papers in scientific periodicals, we should regard it as one of the most salient points in Geology. 1 It may be well further to introduce the subject by a few extracts from Lyell's work above referred to. " The sediment with which the waters are charged is ex- tremely fine, being derived from the destruction of cliffs of red sandstone and shale, belonging chiefly to the coal measures. On the borders of even the smallest estuaries communicating with a bay, in which the tides rise sixty feet and upwards, large areas are laid dry for nearly a fortnight between the spring and neap tides, and the mud is then baked in summer by a hot sun, so that it becomes solidified and traversed by cracks caused by shrinkage. Portions of the hardened mud may then be taken up and removed without injury. On ex- amining the edges of each slab we observe numerous layers, formed by successive tides, usually very thin, sometimes only one-tenth of an inch thick, of unequal thickness, however, because, according to Dr. Webster, the night tides rising a foot higher than the day tides throw down more sediment. When a shower of rain falls, the highest portion of the mud- covered flat is usually too hard to receive any impressions ; while that recently uncovered by the tide, near the water's edge, is too soft. Between these areas a zone occurs almost as smooth and even as a looking-glass, on which every drop forms a cavity of circular or oval form ; and if the shower be 1 Journal of 'London Geological Society, vol. vii. p. 239. MARKINGS, FOOTPRINTS AND FUCOIDS 313 transient, these pits retain their shape permanently, being dried by the sun, and being then too firm to be effaced by the action of the succeeding tide, which deposits upon them a new layer of mud. Hence we find, on splitting open a slab an inch or more thick, on the upper surface of which, the marks of recent rain occur, that an inferior layer, deposited perhaps ten or fourteen tides previously, exhibits on its under surface perfect casts of rain prints which stand out in relief, the moulds of the same being seen in the layer below." After mentioning that a continued shower of rain obliterates the more regular impressions, and produces merely a blistered or uneven surface, and describing minutely the characteristics of true rain marks in their most perfect state, Sir Charles adds : " On some of the specimens the winding tubular tracks of worms are seen, which have been bored just beneath the surface. Sometimes the worms have dived beneath the sur- face, and then re-appeared. Occasionally the same mud is traversed by the footprints of birds (Tringa minuta), and of musk-rats, minks, dogs, sheep and cats. The leaves also of the elm, maple and oak trees have been scattered by the winds over the soft mud, and having been buried under the deposits of succeeding tides, are found on dividing the layers. When the leaves themselves are removed, very faithful im- pressions, not only of their outline, but of their minutest veins, are left imprinted on the clay." This is a minor illustration of that application of recent causes to explain ancient effects of which the great English geologist was the apostle and advocate, and which he so admirably practised in his own work. It is also an illustration of the fact that things the most perishable and evanescent may, when buried in the crust of the earth, become its most durable monuments. Footprints in the sand of the tidal shore are in the ordinary course of events certain to be obliterated 314 MARKINGS, FOOTPRINTS AND FUCOIDS by the next tide ; but when carefully filled up by gently de- posited new material, and hardened into stone, there is no limit to their duration. Let us inquire how this may take place, and the tidal flats of the Bay of Fundy and Basin of Minas may supply us with the information desired. In the upper parts of the Bay of Fundy and its estuaries the rise and fall of tide, as is well known, are excessive. I quote the following description of the appearance they present from a work of earlier date : "The tide wave that sweeps to the north-east, along the Atlantic coast of the United States, entering the funnel-like mouth of the Bay of Fundy, becomes compressed and elevated, as the sides of the bay gradually approach each other, until in the nairower parts the water runs at the rate of six or seven miles per hour, and the vertical rise of the tide amounts to sixty feet or more. In Cobequid and Chiegnecto Bays these tides, to an unaccustomed spectator, have rather the aspect of some rare convulsion of nature than of an ordinary daily phenomenon. At low tide wide flats of brown mud are seen to extend for miles, as if the sea had altogether retired from its bed ; and the distant channel appears as a mere strip of muddy water. At the commencement of flood a slight ripple is seen to break over the edge of the flats. It rushes swiftly forward, and, covering the lower flats almost instantaneously, gains rapidly on the higher swells of mud, which appear as if they were being dissolved in the turbid waters. At the same time the torrent of red water enters all the channels, creeks and estuaries ; surging, whirling, and foaming, and often having in its front a white, breaking wave, or * bore,' which runs steadily forward, meeting and swallowing up the remains of the ebb still trickling down the channels. The mud flats are soon covered; and then, as the stranger sees the water gaining with noiseless and steady rapidity on the steep sides of banks and cliffs, a sense of insecurity creeps over him, as if no limit MARKINGS, FOOTPRINTS AND FUCOIDS 315 could be set to the advancing deluge. In a little time, how- ever, he sees that the fiat, * Hitherto shalt thou come, and no farther,' has been issued to the great bay tide : its retreat com- mences, and the waters rush back as rapidly as they entered. " The rising tide sweeps away the fine material from every exposed bank and cliff, and becomes loaded with mud and extremely fine sand, which, as it stagnates at high water, it deposits in a thin layer on the surface of the flats. This layer, which may vary in thickness from a quarter of an inch to a quarter of a line, is coarser and thicker at the outer edge of the flats than nearer the shore ; and hence these flats, as well as the marshes, are usually higher near the channels than at their inner edge. From the same cause, the more rapid de- position of the coarser sediment, the lower side of each layer is arenaceous, and sometimes dotted over with films of mica, while the upper side is fine and slimy, and when dry has a shining and polished surface. The falling tide has little effect on these deposits, and hence the gradual growth of the flats, until they reach such a height that they can be overflowed only by the high spring tides. They then become natural or salt marsh, covered with the coarse grasses and carices which grow in such places. So far the process is carried on by the hand of nature ; and before the colonization of Nova Scotia, there were large tracts of this grassy alluvium to excite the wonder and delight of the first settlers on the shores of the Bay of Fundy. Man, however, carries the land - making process farther ; and by diking and draining, excludes the sea water, and produces a soil capable of yielding for an indefinite period, without manure, the most valuable cultivated grains and grasses." The mud of these great tidal flats is at the surface of a red colour, and so fine that when the tide leaves it and its surface becomes dry, it shines in the sun as if polished. It is thus capable of taking the finest impressions. When the tide is in, s. E. 23 3l6 MARKINGS, FOOTPRINTS AND FUCOIDS numerous small fish of various species occupy the ground and may leave marks of their fins and tails as they gambol or seek their food. Shell fishes, worms, and Crustaceans scramble over the same surface, or make burrows in it. As the tide recedes flocks of sandpipers and crows follow it down, and leave an infinity of footprints, and even quadrupeds like the domestic hog go far out at low water in search of food. It is said that in some parts of the Bay the hogs are so assiduous in this pursuit that they even awake and go out on the flats in the night tide, and that they have so learned to dread the dangers of the flood, that when in the darkness they hear the dull sound of the approaching bore, they squeal with fear and rush madly for the shore. If we examine it minutely, we shall find that the tidal de- posit is laminated. The tidal water is red and muddy, and holds in suspension sediment of various degrees of coarseness. This, undergoes a certain process of levigation. In the first run of the flood the coarser material falls to the bottom. As its force diminishes the finer material is deposited, and at full tide, when the current has ceased, the finest of all settles, forming a delicate coat of the purest and most tenacious clay. Thus, if a block of the material is taken up and allowed to dry, it tends to separate into thin laminae, each of which re- presents a tide, and is somewhat sandy below, and passes into the finest moulding clay above. The tracks and impressions preserved are naturally made on the last or finest deposit, and filled in with the coarser or more sandy of the next tide. But this may take place in different ways. Impressions made under water at flood tide, or on the surface left bare by the ebb, may in favourable localities be sufficiently tenacious or firm to resist the abrading action of the flood, and may thus be covered and preserved by the next layer, and in this way they may be seen on splitting up a block of the dried mud. But in shallow places and near the shore, where the deposit MARKINGS, FOOTPRINTS AND FUCOIDS 317 has time to consolidate and become dried by the sun and air before the next tide, much better impressions are preserved ; and lastly, on those parts of the shore which are reached only by the spring tides, the mud of the highest tide of course may have several days to harden before the next tide reaches it, and in this case it becomes cracked by an infinity of shrinkage cracks, which, when it is next covered with the tide, are filled with new sediment. In this way is produced in great perfec- tion that combination of footprints, or even of impressions of rain, with casts of cracks, which is so often seen in the older rocks. Where on the sides of channels or near the shore'the mud has a considerable slope, another and very curious effect results. As the tide ebbs the water drains off the surface, or oozing out of the wet sand and mud, forms at the top of the bank minute grooves often no larger than fine threads. These coalesce and form small channels, and these, again, larger ones, till at low tide the whole sloping surface is seen to be covered with a smooth and beautiful tracery resembling the rivers on a map, or the impressions of the trunks and branches of trees, or the fronds of gigantic seaweeds. These " rill marks," as they have been called, are found in great abundance in the coal formation and triassic sandstones and shales, and I am sorry to say, have often been named and described as Fucoids, and illustrated by sumptuous plates. Sometimes these im- pressions are so fine as to resemble the venation of leaves, sometimes so large as to simulate trees, and I have even seen them complicated with shrinkage cracks, the edges of which were minutely crenulated by little rills running into them from the surface. It is further to be noticed that all these markings and im- pressions on tidal shores may, when covered by succeeding deposits, appear either in intaglio or relief. On the upper surface they are of course sunken, but on the lower surface of the bed deposited on them they are in relief. It often happens 3l8 MARKINGS, FOOTPRINTS AND FUCOIDS also that these casts in relief are the best preserved. This arises from the fact that the original moulds or impressions are usually made in clay, whereas the filling material is sandy, and the latter, infiltrated with calcareous or siliceous matter, may become a hard sandstone, while the clay may remain a comparatively soft shale. This tendency of casts rather than of moulds to be preserved sometimes produces puzzling effects. A cylindrical or branching trail thus often assumes the appear- ance of a stem, and any pits or marginal impressions assume the form of projections or leaves, and thus a trail of a worm or Gastropod or a rill mark may easily simulate a plant. It is to be observed, however, that these prominent casts are on the under side of the beds, that their material is continuous with that of the beds to which they belong, and that they are destitute of any carbonaceous matter. There are, however, cases where markings may be in relief, even on the upper surfaces of beds. The following are illustrations of this. Just as a man walking in newly fallen snow compresses it under his feet, and if the snow be afterwards drifted away or melted away by the sun, the compressed part resists longest, and may appear as a raised footmark, so tracks made on soft material may consolidate it so that if the soft mud be afterwards washed away the tracks may remain projecting. Again, worms eject earthy matter from their burrows, forming mounds, patches or raised ridges of various forms on the surface, and some animals burrow immediately under the surface, pushing up the mud over them into a ridge, while others pile up over their bodies pellets of clay, forming an archway or tunnel as they go. Zeiller has shown that the mole cricket forms curious roofed trails of this kind, and it seems certain that Crustaceans and marine worms of different kinds execute similar works, and that their roofed burrows, either entire or fallen in, produce curious imitations of branches of plants. The great and multiform army of the sea worms is indeed MARKINGS, FOOTPRINTS AND FUCOIDS 319 the most prolific source of markings on sea-formed rocks. Sometimes they cover very large surfaces of these, or penetrate the beds as perforations, with tortuous furrows, or holes per- fectly simple, or marked with little striae made by bristles or minute feet, sometimes with a fringe of little footmarks at each side, sometimes with transverse furrows indicating the joints of the animal's body. Multitudes of these markings have been described and named either as plants or as worm- tracks. Again, these creatures execute subterranean burrows, sometimes vertical, sometimes tortuous. These are often mere cylindrical holes afterwards filled with sand, but some- times they have been lined with a membranous tube, or with the rejectamenta of the food of the animals, or with little fragments of organic matter cemented together. Sometimes they open on the surface as simple apertures, but again they may be surrounded with heaps of castings, sometimes spiral in form, or with dumps of sand produced in their excavation, and which may assume various forms, according to circum- stances. Sometimes the aperture is double, so that they seem to be in pairs. Sometimes, for the convenience of the animal, the aperture is widened into the form of a funnel, and some- times the creature, by extending its body and drawing it in, surrounds its burrow with a series of radiating tracks simulat- ing the form of a starfish or sea anemone, or of the diverging branches of a plant. Creatures of higher grade, provided with jointed limbs, naturally make their actions known in more complicated ways. Some years ago I had the pleasure of spending a few weeks at the favourite sea-side resort of Orchard Beach on the New England coast, and there made my first acquaintance with that very ancient and curious creature the Limulus, or Horse-shoe Crab, or King-crab, as it is sometimes called. Orchard Beach is, I presume, near its northern range on our coast, and the specimens seen were not very large in size, though by no means 320 MARKINGS, FOOTPRINTS AND FUCOIDS rare, and not infrequently cast on shore in storms. But the best facilities for studying their habits were found in a marsh at no great distance from the hotel, where there were numerous channels, ditches and little ponds filled with sea water at high tide. In these were multitudes of young Limuli, varying from an inch to three or four inches in breadth, and though many were dead or merely cast shells, it was easy to take young specimens with a landing net. A number of these were se- cured, and I made it my business for some time to study their habits and mode of life, and especially the tracks which they made in sand or mud. The King-crab, viewed from above, consists of three parts. The anterior shield or carapace is semi-circular in form, with two spines or projecting points at the angles, raised in the middle and sloping down to a smooth or moderately sharp edge in front. The eyes are set like windows in this shield. Two large ones at the sides, which are compound eyes con- sisting of numerous ocelli or little eyes, and two microscopic ones in front, at the base of a little spine, which are simple. The second or abdominal part is also in one piece, somewhat quadrate in form, with ridges and serratures at the sides armed with spines, and which may be said to simulate the separate joints into which the abdomen of an ordinary Crustacean is divided. The third part is a long tail spine, triangular in cross section, sharply pointed, and so jointed to the posterior end of the abdomen that it can be freely moved in any direction as a bayonet-like weapon of defence. When unable to escape from an enemy it is the habit of the creature to double itself up by bending the abdomen against the carapace, and erecting the sharp spine. Thus, with fixed bayonet it awaits attack, like the kneeling soldier in front of a square. Below this upper shield, which is thin and papery in the young, somewhat horny in the adult, are the numerous limbs of the creature, with which we are at present most concerned. MARKINGS, FOOTPRINTS, AND FUCOIDS 321 Under the carapace are several pairs of jointed limbs differing in size and form. The two anterior are small and peculiarly formed claws, used apparently in manipulating the food. The four next are larger in size, and are walking feet, each furnished with two sharp points which form a pincer for holding. The last pair is much larger and stronger than any of the others, and armed not only with a pair of pincers, but with four blunt nail- like points. Under the abdomen are flat swimming feet, as they have been called, each composed of a broad plate notched and divided in the middle. When at rest these lie flat on each other, but they can be flapped back and forth at the will of the animal. Let us now see what use the creature can make of these numerous and varied pedal appendages, and for distinctness' sake we shall call the anterior set thoracic and the posterior abdominal. When placed in shallow water on fine sand it walked slowly forward, and its tracks then consisted of a number of punctures on the sand in two lines. If, however, the water was very shallow or the sand very soft or inclined upward the two edges of the carapace touched the bottom, making a slight furrow at each side ; and if the tail was trailed on the bottom, this made a third or central furrow. When climbing a slope, or when placed at the edge of the water, it adopted another mode of locomotion, pushing with great force with its two posterior limbs, and thus moving forward by jerks. It then made four deep marks with the toes of each hind limb, and more or less interrupted marks with the edges of the cara- pace and the tail. In these circumstances the marks were al- most exactly like those of some forms of the Protichnites of the Potsdam sandstone. When in sufficiently deep water and de- sirous to escape, it flapped its abdominal feet, and then swam or glided close to the bottom. In this case, when moving near the soft bottom, it produced a series of transverse ridges and furrows like small ripple marks, with a slight ridge in the middle, 322 MARKINGS, FOOTPRINTS AND FUCOIDS and sometimes, when the edges of the carapace touched the bottom, with lateral furrows. In this way the animals were able to swim with some ease and rapidity, and on one occasion I observed an individual, confined in a tub of water, raise itself from the bottom and swim around the tub at the surface in search of a way of escape. Lastly, the young Limuli were fond of hiding themselves by burrowing in the sand. They did this by pushing the anterior rounded end of the carapace under the sand, and then vigorously shovelling out the material from below with their feet, so that they gradually sank under the surface, and the sand flowed in upon them till they were entirely covered. If carefully removed from the hollow they had made, this was found to be ovoid or hoof shaped in form and bilobed, not un- like the curious hollows (Rusophycus Grenvillensis of Billings) which I have supposed to be burrows of Trilobites. I thus found that the common King-crab could produce a considerable variety of tracks and burrows comparable with those which have been named Protichnites, Climactichnites, Bilobites, Cruziana, Rusichnites, etc. ; and that the kind of markings depended partly on the differences of gait in the animal, and partly on the circumstances in which it was placed ; so that different kinds of tracks do not always prove diversity in the animals producing them. The interest of this investigation as applied to Limulus is increased by the fact that this creature is the near ally of Trilobites, Eurypterids and other Crustaceans which were abundant in the earlier geological ages, and whose footprints are probably among the most common we find on the rocks. Lastly, on this part of the subject, it is to be observed that many other marine animals, both crustaceans and worms, make impressions resembling in general character those of Limulus. In addition to those already mentioned, Nathorst and Bureau have shown that various kinds of shrimps and lobster-like Crustaceans, when swimming rapidly by successive strokes of RUSICHNITES GRENVII.LENSIS, Billings a " Bilobitc." Probably the Cast of a Crustacean burrow. MARKINGS, FOOTPRINTS AND FUCOIDS 323 the tail, make double furrows with transverse ridges resembling those of Bilobites, and there are even some mollusks which by the undulations of the foot or the hook-like action of its an- terior part, can make similar trails. A question arises here as to the value of such things as fossils. This depends on the fact that many creatures have left their marks on the rocks when still soft on the sea bottom, of which we have no other indica- tions, and it also depends on our ability to understand the import of these unconscious hieroglyphics. They will certainly be of little use to us so long as we persist in regarding them as vegetable forms, and until we have very carefully studied all kinds of modern markings. 1 Nor does it seern of much use to assign to them specific names. The same trail often changes from one so-called species, or even genus, to another in tracing it along, and the same animal may in different circumstances make very different kinds of tracks. There will eventually, perhaps, arise some general kind of nomenclature for these markings under a separate sub-science of Ichnology or the doc- trine of Footprints. I have said nothing of true Algae or seaweeds, of which there are many fossil species known to us by their forms, and also by the carbonaceous or pyritous matter, or discharge of colour from the matrix, which furnishes evidence of the presence of organic material ; nor of the marks and trails left by sea- weeds and land plants drifting in currents, some of which are very curious and fantastic ; nor of those singular trails referred to the arms of cuttlefishes and the fins of fishes, or to sea jellies and starfishes. These might form materials for a treatise. My object here is merely to indicate the mode of dealing with such things, and the kind of information to be derived from them. When we come to the consideration of actual footprints of 1 Geologists are greatly indebted to Dr. Nathorst of Stockholm for his painstaking researches of this kind. 324 MARKINGS, FOOTPRINTS AND FUCOIDS vertebrate animals having limbs, the information we can obtain is of a far more definite character. This has already been re- ferred to in treating of the first Air-breathers in a previous chapter. One very curious example we may close with. It is that of the celebrated " bird tracks " of the sandstone quarries in the Trias of Connecticut and Massachusetts. These tracks, of immense size, as much as eighteen inches in length, and so arranged as to indicate the stride of a long-legged biped, were naturally referred to gigantic birds, allied to modern waders. But when it was found that some of them showed a central furrow indicating a long tail trailing behind, this conclusion was shaken, and when in tracing them along, places were found where the animal had sat down on its haunches and the end of its tail, and had brought down to the ground a pair of small fore feet with four or five fingers, it was discovered that we had to deal with biped reptiles ; and when the tracks were correlated with the bones of the extinct reptiles known as Dinosaurs, we found ourselves in the presence of a group of the most strange and portentous reptilian forms that the earth has ever known. Marsh has been enabled, by nearly perfect skeletons of some allied reptilian bipeds found in the West, to reproduce them in their exact forms and proportions, so that we can realize in imagination their aspect, their gait, and their gigantic propor- tions. Examples of this putting together of footprints and osseous remains of vertebrate animals are not rare in the history of geology, and show us how the monsters of the ancient world, equally with their human successors, could leave " footprints on the sands of time." The Dinosaurs which have left their footprints on the sand- stones of Connecticut and Massachusetts are, however, greatly more numerous than those known to us by osseous remains. Thus footprints have the further use of filling up the imperfec- tions of our geological record, or at least of pointing out gaps which but for them we might not have suspected. The re- MARKINGS, FOOTPRINTS AND FUCOIDS 325 markable inferences of Matthew already referred to, respecting cuttlefishes in the Cambrian period, constitute a case in point. Footprints of Batrachians in the Carboniferous rocks were known before their bones. The strange hand-like tracks in the Trias were known before we knew the Labyrinthodon that produced them. We are still ignorant of the animals whose tracks in the old Potsdam sandstones we name Protichnites. REFERENCES : On Rusichnites (a form of Bilobite), Canadian Naturalist, 1864. On Footprints of Limulus compared with Protichnites, etc. Ibid. On Footprints and Impressions of Aquatic Animals and Imita- tive Markings, Anier. Journal of Science, 1873. On Burrows and Tracks of Invertebrate Animals, Quarterly Journal of Geological Society^ 1890. On Footprints of Carboniferous Batrachians. "Acadian Geology," "Air-breathers of the Coal Period," etc. PRE-DETERMINATION IN NATURE. DEDICATED TO THE MEMORY OF ELKANAH BILLINGS, FIRST PALAEONTOLOGIST OF THE GEOLOGICAL SURVEY OF CANADA, WHO LAID THE FOUNDATIONS OF OUR KNOWLEDGE OF THE INVERTEBRATE FOSSILS OF CANADA. FIXITY OF LAWS AND PROPERTIES OF ENERGY AND MATTER PERMANENCE OF CONTINENTS AND OCEANS THE PERMANENT AND THE CHANGEABLE - PERMANENCE OF ANIMAL AND VEGETABLE FORMS AND STRUCTURES PRINCIPLES OF CONSTRUCTION IN THE PARTS OF TRILO- BITES IN THE SKELETONS OF SPONGES IN EARLY VERTEBRATES IN PLANTS LAWS OF FIXITY AND DIVERSITY S. E. RESTORATION OF PROTOSPONGIA TETRANEMA. Quebec group; Giluru-Cambrian, Little Metis (p. 335). CHAPTER XII. PRE-DETERMINATION IN NATURE. THE natural prejudice of persons not acquainted with geology is that in the world all things continue as they were from the beginning. But a little observation and experi- ence dispels this delusion, and perhaps replaces it with an opposite error. When our minds have been familiarized with the continuous processes by which vaporous nebulae may be differentiated into distinct planets, and these may be slowly cooled from an incandescent state till their surfaces become resolved into areas of land and water ; and still more, when we contemplate the grand procession of forms of life from the earliest animals and plants to man and his contemporaries, we become converts to the doctrine that all things are in a per- petual flux, and that every succeeding day sees them different from what they were the day before. In this state of mind the scientific student is apt to overlook the fact that there are many things which remain the same through all the ages, or which, once settled, admit of no change. I do not here refer to those fundamental properties of matter and forces and laws of nature which form the basis of uniformitarianism in geology, but to determinations and arrangements which might easily have been quite different from what they are, but which, once settled, seem to remain for ever. We have already considered the great fact that the nuclei and ribs of the continental masses were laid down as foundations in the earliest periods, and have been built upon by determi- 330 PRE-DETERMINATION IN NATURE nate additions, more especially upon their edges and their hollows, so that while there has been a constant process of removal of material from the higher parts of the land, and deposition in the sea, and while there have been periodical elevations and subsidences, the great areas of land and water have remained substantially the same, and the main lines of elevation and folding have conformed to the directions origin- ally fixed. Thus, in regard to the dry land itself, there has been fixity, on the one hand, and mutation on the other, of a most paradoxical aspect, till we understand something of the great law of constant change united with perennial fixity in nature. From want of attention to this, the permanence of continents is still a debated question, and it is difficult for many to understand how the frequent dips of the continental plateaus and margins under the sea, and their re-elevation, often along with portions of the shallower sea bottom, can be consistent with a general permanence of the position of the continents and of the corresponding ocean abysses ; yet, when this is properly understood, it becomes plain that the union of fixity with changes of level has been a main cause of the continuity and changes of organic beings. Only the submerg- ence of inland plateaus under shallow and warm waters could have given scope for the introduction of new marine faunas, and only re-elevation could have permitted the greatest extension of plants and animals of the land. Thus, the con- tinuity of life with continual advance has depended on the permanent existence of continental and oceanic areas ; and the continents that remain to us with all their diversity of elevation and outline, their varied productions, both mineral and organic, and their life, which is a select remainder of all that went before, have been produced and furnished by a succession of changes, modified by the most conservative retention of general arrangements and forms. It is evident, however, that it is not merely permanence we. PRE-DETERMINATION IN NATURE 331 have to deal with here, but permanence of position along with change of elevation ; and this modified by the fact that there have always been mountain ridges, internal plateaus, and mar- ginal areas affected in various ways by the vertical movement of the land. Further, the elevation and subsidence of the land have not always been uniform, but often differential, while every movement has tended to produce modifications of ocean cur- rents and of atmospheric conditions. The whole subject, more especially in its relations to life, thus becomes very complicated, and it is perhaps in consequence of partial and imperfect views on these points that so much diversity of opinion has arisen. For example, it is evident that we can gain nothing by adding to the continents those submerged margins delineated by Murray in the Challenger reports, and which have in periods of continental elevation themselves formed portions of the land. Nor do we establish a case in favour of perished oceanic conti- nents by the argument that they are needed to furnish the materials of marginal mountains which are due to the con- tinuous sweeping of arctic material to the south by currents, as we see in the coast of North America to-day. Nor do we in- validate the permanence of the continents by the bridges of land, islands, and shallow water at various times thrown across the Atlantic. The distribution of Cambrian Trilobites, as illus- trated by Matthew, 1 seems to show a bridge of this kind in the north in very early times, and similar evidence is furnished by the animals and plants of the Devonian and Carboniferous, and by the sea animals and plants of the later Tertiary and modern. Gardener has postulated a southern bridge in the region of the West Indies for the migrations of plants, and Gregory has adduced the evidence of those conservative and slow-moving creatures, the sea urchins, in favour of similar con- nection in the West Indian region at two distinct periods of time (the Lower Cretaceous and the Miocene Tertiary). But 1 Transactions Royal Society of Canada, 1892. 33 2 PRE-DETERMINATION IN NATURE bridges do not involve want of permanence in their termini. Because an engineer has bridged the Firth of Forth, it does not follow that the banks of this inlet did not exist before the bridge was built ; and if the bridge were to perish, the evidence that trains had once passed that way would not justify the belief that the bed of the Firth had been dry land, and the areas north and south of it depressed. The more we consider this question the more we see that the permanence, growth and sculpture of the continents are parts of a great continuous and far-reaching plan. This view is strengthened rather than otherwise, when we consider the probable manner in which the enormous weight of the continents is sustained above the waters. We may attribute this, on the one hand, to rigidity and lateral arching and compression, or, on the other, to what may be termed flotation of the lighter parts of the crust ; and there seems to be little doubt that both of these principles have been employed in constructing the "pillars which support the earth." It is evident, however, that an arch thrown over the internal abyss of the earth, or a portion of its crust so lightened as to be pressed upward by its heavier surroundings, must, when once established, have become a permanent feature of the earth's foundations, not to be disturbed without calamitous conse- quences to its inhabitants. It is the part of the philosophical naturalist to bring together these apparent contrarieties of mutation and permanence ; both of which are included, each in its proper place, in the great plan of nature. It is therefore my purpose in the present chapter to direct attention to some of the terminal points or fixed arrangements that we meet with in the course of the geological history, and even in its earlier parts, and more par- ticularly in reference to the organic world. This, which is in itself constantly changing, has been placed under necessity to adhere to certain determinations fixed of old, and which regulate its forms and possibilities down to our own time. PRE-DETERMINATION IN NATURE 333 The argument, as we have seen in a previous chapter, for the animal nature of Eozoon depends on our assuming certain parts of this fixity. We suppose that then as now calcium carbonate had been selected as the material for the skeletons of such creatures ; that then, as now, minute tubuli and large canals were necessary to enable the soft animal matter to per- meate and pass through the skeleton, and that the protoplas- mic animal matter of these far back geological periods had the same vital properties of contraction and extension, digestion, etc., that it has to-day. Could any one prove that these determina- tions of vital and other forces had not been established, or that living protoplasmic matter, with all its wonderful properties, had not been constructed in the Laurentian period, the exist- ence of this ancient animal would be impossible. Yet how much is implied in all this, and though nothing is more un- stable chemically or vitally than protoplasm, if it were intro- duced in the Laurentian, it has continued practically unchanged up to the present time. If we pass on to the undoubted and varied life of the Cambrian period, we shall find that multitudes of things which might have been otherwise were already settled in a way that has required no change. In the oldest Trilobites the whole of the mechanical con- ditions of an external articulated skeleton had been finally settled. The material chitinous or partly calcareous, its micro- scopic structure, fitted to combine lightness and strength with facility for rapid growth, the subdivision of its several rings, so as to form a protective armour and a mobile skeleton, the arrangement of its spines for defence without interfering with locomotion, the contrivance of hinge joints arranged in different planes in the limbs, all these were already in full perfection, and just as they are found to-day in the skeleton of a king- crab or any other Crustacean. They have, it is true, been modified into a vast number of subordinate forms and uses, 334 PRE-DETERMINATION IN NATURE but the general principles and main structures all stand. I was much struck with this recently in studying a remarkable specimen now in the National Museum at Washington. It is a large species of Asaphus; the same genus which gave to the late Mr. Billings the limbs of a Trilobite, the first ever de- scribed ; but in the Washington specimen they are remarkably perfect. Each limb presents a series of joints resembling those of the tarsus of an insect, each joint being of conical form with the narrow proximal end articulated to the enlarged distal end of the previous one, so as to give great facility of movement and accommodation for delicate muscular bands. This tells us of muscular fibre and tendon fitted for flexing and extending these numerous joints, of motor nerves to work that marvellous contractile power of the striated muscle, whose mode of action is still an insoluble mystery, yet one practically solved in the remote Cambrian age for the benefit of these humble inhabitants of the sea. If we could imagine that the inventive power to perfect such machinery was pre- sent in the brains of these old Crustaceans or Arachnidans, we might wish that some of them had survived to instruct us in matters which baffle our research. It is long since the compound eyes of these Trilobites, as illustrated by Burmeister, gave Buckland the opportunity to infer that the laws of light and of vision were the same from the first as now. But what does this imply ? Not only that the light of the sun penetrating to the depths of the Cambrian sea, was regulated by the same laws as to-day, but that a series of cameras was perfected to receive the light as reflected from objects, to picture the appearance of these objects on a retinal screen as sensitive as the film of the photographer, and thereby to produce true perceptions of vision in the sensorium of these ancient animals. I have before me a fragment of the eye of a Trilobite (Phacops\ in which may be seen the little radiating tubes provided for the several ocelli of the compound eye, just PRE-DETERMINATION IN NATURE 335 as we see in the modern Limulus; and each of these ocelli must have been a perfect photographic camera, and more than this, since absolutely automatic, and probably having the power to represent colour as well as light and shade. We know also, from the recent experiments of an Austrian physiologist on the eyes of insects, that such compound eyes are so constructed as to present a single picture, just as we can see the whole landscape in looking through the many little panes of a cottage window. In our own time the king-crab and lobster no doubt see just as their predecessors did millions of years ago, and with precisely similar instruments. But the eyes of the modern Crustaceans have to compete with eyes of a dissimilar type, constructed on the same general optical principles, but quite different in detail. These are the simple or single eyes of the cuttlefishes and the true fishes. The same rivalry existed in the oldest seas, when the com- petition of Crustaceans and cuttles was just as keen as now. Though the eyes of the latter have not been preserved, or at least have not yet been found, we have a right to infer that the cuttles of the Cambrian and Silurian seas must have been able to see as well as their Crustacean foes and competitors. If so, the other type of eye must have been perfected for aquatic vision as early as the compound type. In any case we know that a little later, in the Carboniferous period, we have evidence that the eyes of fishes conformed to those of their modern suc- cessors. I have myself described l a carboniferous fish (Palcz- oniscus) from the bituminous shales of Albert County, New Brunswick, in which the hard globular lens of the eye had been sufficiently firm and durable to retain its form, and to be re- placed by calcite, showing even that like the lens of the eye of a modern fish it had been constructed of concentric laminae. In the Carboniferous period also, both types of eye, the com- pound and the single, experienced the further modifications 1 Canadian Naturalist, 336 PRE-DETERMINATION IN NATURE necessary to fit them for vision in air, the compound eye in insects, the simple eye in Batrachians. 1 The original photo- graphic cameras, strange though this may appear to us, were intended for use under water ; but at a very early time they were adapted to work in air. But we must bear in mind that this early solving of advanced problems in mechanics, optics and physiology was in favour of Crustaceans and cuttles, which were lords of creation in their time. There were in those early days humbler creatures whose structures also present wonderful contrivances. I have already referred, in the chapter on imperfection of the geological record, to the fossil sponges which have been found in so great number and perfection in some of the oldest rocks of Canada, and which have for the first time enabled us to appreciate the forms and structures of the wonderful silicious sponges which preceded those with which the dredgings of the Challenger\\w, made us familiar in the modern seas. Humble sarcodous animals, without distinct muscular or nervous system or external senses, the sponges have at least to live and grow, and to that end they must already, in the dawn of life on our planet, 2 have perfected those arrangements of ciliated cells in chambers and canals which the microscope shows us driv- ing currents of water through the modern sponges, and thereby bringing to them the materials of food and means of respira- tion. It is true we know as little as the sponges themselves of the modus operandi of those perpetually waving threads which we call cilia or flagella, yet they must have existed with all their powers even before the Cambrian period. 3 1 See ante, chapter on Air-breathers. 2 I have found spicules of sponges in the chert nodules from the If uronian limestones of Canada. 3 Many species of hexaclinelled sponges have have been described from the upper Cambrian or lower Cambro-Silurian of Canada. See paper by the author in the Transactions of the Royal Society of Canada, 1889. A GIANT NET-SPONGE. Palceosaccus Dawsoni, Hinde. From the Quebec group (Ordovician), Little Metis, Canada. Reduced to $ the diameter. (From the Geological Magazine, 1803.) PRE-DETERMINATION IN NATURE 337 The sponge, in order to support its delicate protoplasmic structures, must have a skeleton. In modern times we find these creatures depositing corneous or horny fibres, as in the common washing sponges, or forming complex and beautiful structures of needles, or threads of silica or calcite, and they seem from the first to have been able to avail themselves of all these different materials. The oldest species that we know had silicious or calcareous skeletons, though some of them must also have had a certain amount, at least, of the ordinary spongy or corneous fibres. But the most astonishing feature in what remains of their skeletons, flattened out as they are on the surfaces of dark slaty rock, is the manner in which they worked up so refractory a material as silica into fibres like spun glass rods and crosses, and built these up into beautiful basket- like forms, globular, cylindrical or conical. It was necessary that they should fix themselves on the soft muddy bottoms on which they grew, and to this end they produced slender silicious fibres or anchoring rods, which, fine though they were, had the form of hollow tubes. Sometimes a single rod sufficed, but in this case it had a crosslike anchor affixed to its lower end, to give it stability. Sometimes there were several simple rods, and then they were skilfully braced by spreading them apart at the ends, and by flattening their extremities into blades. Sometimes four rods joined in a loop at the end gave the required support. Some larger species wound together many threads like a wire rope, and even added to this flanges like the thread of a screw, anticipating the principle of the modern screw pile. The body of the sponge must be hollow within, and must have a large aperture or opening for the discharge of water, and smaller pores for its admission. Various general forms were adopted for this. Some were globular, or oval, or pear-shaped ; others cylindrical, concave, or mitre-shaped. To give form and strength to these shapes there were sometimes vertical and 338 PRE-DETERMINATION IN NATURE transverse rods soldered together. In other cases there were four- rayed or six-rayed needles of silica, with their points attached so as to form a beautiful lattice-work, with its meshes either square or lozenge-shaped. For protection sharp needles were arranged like chevaux defrize at the sides and apertures, and these last were sometimes covered with a hood or grating of needles, to exclude intruders from the interior cavity. Other species, however, like some in the modern seas, seemed to despise these niceties, and contented themselves with long straight needles placed in bundles, or radiating from a centre, and thus supporting and protecting their soft and sensitive protoplasm. Curiously enough, these old sponges did not avail them- selves of the natural cystallization of silica, which, left to itself, would have formed six-rayed stars, with the rays at angles of sixty degrees, or six-sided plates, rods, or pyramids. They adopted another and peculiar form of the mineral, known as colloidal silica, and being thus relieved from any need to be guided by its crystalline form, treated it as we do glass, and shaped it into cylindrical tubes, round needles and stars or crosses, with the rays at right angles to each other. The sponges whose skeletons are thus constructed, and which, anticipated so many mechanical contrivances long afterwards devised by man, belonged to a group of silicious sponges {Hexaclinellidcz) which is still extant, and represented by many rare and beautiful species of the deep sea, which are the ornaments of our museums, and of which the beautiful Eupleectella or Venus flower-basket, from the Philippine Islands, and the glass-rope sponge (Hyalonema), from Japan, are examples. But contemporary with these there was another group (Lithistidcz), constructing skeletons of carbonate of lime, and which preferred, instead of the regular mechanical struc- tures of the others, a kind of rustic work, made up of irregular fibres, very beautiful and strong, but as a matter of pattern and taste standing quite by itself. If there were any sponges with PRE-DETERMINATION IN NATURE 339 altogether soft and spongy skeletons in these old times, their remains do not seem to have been preserved. Here, it will be observed, are a great variety of vital and mechanical contrivances devised in the very early history of the earth, settled for all time, and handed down without improve- ment, and with little change, to our later day. They are indeed vastly more wonderful than the above general account can show ; for to go into the details of structure of any one of the species would develop a multitude of minor complexities and niceties which no one not specially a student of these animals could appreciate. These are not solitary cases. The student of fossils meets with them at every turn ; and if he possesses the taste and imagination of a true naturalist, cannot fail to be impressed with them. To turn to a later but very ancient period, what can be more astonishing than those first air-breathing vertebrates of the Coal formation referred to in a previous chapter, with all their special arrangements for an aerial habitat ? I have mentioned their footprints, and when we see the quarrymen split open a slab of sandstone and expose a series of great plantigrade tracks, not unlike those of a human foot, with the five toes well deve- loped, we are almost as much astonished as Crusoe was when he saw the footprints on the sand. Crusoe inferred the presence of another man in his island ; we infer the earliest appearance of an air-breathing vertebrate and the pre-human determination of the form and number of parts of the human foot and hand, to appear in the world long ages afterward. We see also that already that decimal system of notation which we have founded on the counting of our ten fingers was settled in the framework of most unmathematical Batrachians. It has approved itself ever since as the typical and most perfect number of parts for such organs. If sceptically inclined, we may ask, Why five rather than 34O PRE-DETERMINATION IN NATURE four or six ? In the case of man we see that individuals who have lost one finger have the use of the hand impaired, while the few who happen to have six do not seem to be the better. How it was with the old Batrachians we do not know; but it is certain that if we could have amputated the claw-bearing little toe of Sauropus unguifer^ or the reflexed little toe of Cheirothe- rium, we should have much injured their locomotive power. The vegetable kingdom is full of similar examples of the early settlement of great questions. Perhaps nothing is more mar- vellous than the power of the green cells of the leaf as workers of those complex and inimitable chemical changes whereby out of the water, carbon dioxide and ammonia of the soil and the atmosphere, the living vegetable cell, with the aid of solar energy, elaborates all the varied organic compounds produced by the vegetable kingdom. Yet this seems all to have been settled and perfected in the old Silurian period, long before any kind of plant now living was on the earth. Perhaps in some form it existed even in the Laurentian age, and was instru- mental in laying up its great beds of carbon. So all that is essential in plant reproduction, whether in that simpler form in which a one-celled spore is the reproductive organ, or in that more complex form in which an embryo plant is formed in the seed, with a store of nourishment laid up for its susten- ance. These arrangements were obviously as perfect in the great club mosses and pines of the Devonian and Carboniferous as they have ever been since, and we have specimens so preserved as to show their minute parts just as well as in recent plants. The microscope also shows us that the contrivances for thicken- ing and strengthening the woody fibres and trunk of the stem by bars or interrupted linings of ligneous matter, so as to give strength and at the same time permit transudation of sap, were all perfected, down to their minutest details, in the oldest land plants. It is true that flowers with gay petals and some of the PRE-DETERMINATION IN NATURE 341 more complicated kinds of fruit are later inventions, but the additions in these consist mainly of accessories. The essentials of vegetable reproduction were as well provided for from the first. The same principle applies to many of the leading forms and types of life, considered as genera or species. While some of these are of recent introduction, others have continued almost unchanged from the remotest ages. Such creatures as the Lingulae, some of the Crustaceans and of the Mollusks, the Polyzoa and some Corals have remained with scarcely any change throughout geological time, while others have dis- appeared, and have been replaced by new types. We began this chapter with a consideration of the per- manence of continental areas, and may close with a reference to the same great fact in connection with the continuity of life. Whether with some we attach more importance to the support of the continents by lateral pressure and rigidity, or with others to what may be termed flotation, by virtue of their less density, as compared with that of the lower parts of the earth ; there can be little doubt that both principles have been applied, and that both admit of some vertical movement. Thus the stability of the continents is one of position rather than height, and their internal plateaus as well as their partially submerged marginal slopes have undergone great and unequal elevations and depressions, causing most important geographical changes. Among these are the formation of connecting bridges of shoals, islands, or low land, connecting the continental masses at different periods, and permitting migrations of shallow-water animals and even of denizens of the land. The facts adduced in previous pages are sufficient to show connections across the north of the Atlantic at intervals reaching from the Cambrian to the Modern. The conclusion of the whole matter is that there is a fixity and unchangeableness in determinations and arrangements of s. E. 25 342 PRE-DETERMINATION IN NATURE force just as much as in natural laws ; and that while God has made everything beautiful in its time He has also made every- thing beautiful and useful in some sense for all time. With all this, while the great principles and modes of operation remain unchanged, there is ample scope for development, modification and adaptation to new ends, without deviation from essential properties and characters. It is a wise and thoughtful philosophy which can distinguish what is fixed and unchangeable from that which is fluctuating and capable of development. Until this distinction is fully understood, we may expect one-sided views and faulty generalizations in our attempts to understand nature. REFERENCES : "The Chain of Life in Geological Times." London. New Species of Fossil Sponges from the Quebec Group at Little Metis. Trans. Royal Society of Canada, 1889. Fossil Fishes from the Lower Carboniferous of New Brunswick. Canadian Naturalist, "Acadian Geology," 1855, and later editions to 1892. London and Montreal. " The Story of the Earth," 1872, and later editions to 1891. London. THE GREAT ICE AGE. DEDICATED TO THE MEMORY OF MY LATE FRIEND DAVID MILNE HOME, LL.D., F.R.S.E., ETC., AN EMINENT AND JUDICIOUS ADVOCATE OF SOUND AND MODERATE VIEWS RESPECTING THE GLACIAL AGE. EXAGGERATED IDEAS THE ST. LAWRENCE VALLEY MODERN ICE ACTION IN THE ST. LAWRENCE COAST ICE THE ICEBERGS OF BELLE-!SLE MT. BLANC AND ITS GLACIERS EFFECTS OF GLACIERS POSSIBLE EXTENSION OF GLACIERS FACTS OF GLACIATION IN CANADA. COR- DILLERAN GLACIER, LAURENTIDE GLACIER, APPALACHIAN GLACIER; SUBMERGED VALLEYS AND PLAINS DOUBLE SUBMERGENCE AND INTERMEDIATE PARTIAL ELEVATION INTERGLACIAL PERIODS QUESTIONS AS TO ALTERNATE GLACIATION OF NORTHERN AND SOUTHERN HEMISPHERES CHAPTER XIII. THE GREAT ICE AGE. SCIENTIFIC superstitions, understanding by this name w_} the reception of hypotheses of prominent men, and using these as fetishes to be worshipped and to be employed in miraculous works, are scarcely less common in our time than superstitions of another kind were in darker ages. One of these which has been dominant for a long time in geology, and has scarcely yet run its course, is that of the Great Ice Age, with its accompaniments of Continental Glaciers and Polar Ice Cap. The cause of this it is not difficult to discern. The covering of till, gravel and travelled boulders which encumbers the surface of the northern hemisphere from the Arctic regions more than half way to the equator, had long been a puzzle to geologists, and this was increased rather than diminished when the doctrine of appeal to recent causes on the principle of uniformity became current. It was seen that it was necessary to invoke the action of ice in some form to account for these deposits, and it was at the same time perceived that there was much evidence to prove that between the warm climate of the early Tertiary and the more subdued mildness of the modern time there had intervened a period of unusual and extreme cold. In this state of affairs attention was attracted to the Alpine glaciers. Their movement, their erosion of surfaces, their heaping up of moraines bearing some resemblance to the widely extended boulder deposits, their former greater extension, as indicated 34-6 THE GREAT ICE AGE by old moraines at lower levels than those in process of formation, were noted. Here was a modern cause capable of explaining all the phenomena. Men's minds were taken by storm, and as always happens in the case of new and im- portant discoveries, the agency of glaciers was pushed at once far beyond the possibilities of their action under any known physical or climatal laws. This exaggerated idea of the action of land ice in the form of glaciers is not yet exploded, more especially in the United States, where official sanction has been given to it by the Geological Survey, and where it has been introduced even into school and college text books. It affords also a telling bit of scientific sensationalism, which can scarcely be resisted by a certain class of popular writers. America has also afforded greater facilities for extreme theories of this kind, owing to the wide and uninterrupted distribution of glacial deposits, and the more simple and less broken character of its great internal plateau, while the influence of great leading minds, like those of the elder Agassiz and of Dana, naturally held sway over the younger geologists. Fortu- nately Canada, which possesses the larger and more northern half of the North American continent; though numerically inferior, and therefore overborne in the discussion, has, in the main, remained stedfast to facts rather than to specious theories, and has been confirmed in this position by the clearer testimony of nature in a region where many of the features of the glacial age still persist. 1 The writer of these pages has, ever since the publication of the first edition of his " Acadian Geology," 3 steadily resisted the more extreme views of glaciation, and has opposed the southward progress of the great continental glacier. Though, figuratively speaking, overborne and pressed back in the . 1 I may refer here to the recent researches of Dr. G. M. Dawson, Mr. R. Chalmers, Mr. McConnell and Dr. Ells. i ? 1855. THE GREAT ICE AGE 347 course of its extension, he has now, like those primitive men who are imagined in the post-glacial age to have followed up the retreat of the ice, the pleasure of seeing the once formid- able continental glacier broken up into great local glaciers on the mountain ranges separated by intervening areas of submergence. The questions relating to this subject are too numerous and varied for treatment here. The question of the causes of the great lowering of temperature in the glacial age I shall leave for consideration in the next chapter, and merely state here that I believe changes of distribution of sea and land and of ocean currents are sufficient to account for all the refrigeration of which there is good evidence. I content myself with a comparison of the glacial phenomena of Mont Blanc and of the Gulf of St. Lawrence from my own observation, 1 and some general deductions as to glacier possibilities. A scientific voyager carries with him a species of question- ing peculiar to himself. Not content with vacantly gazing at the sea, scrutinizing his fellow passengers, noting the changes of the weather and the length of the day's run, he recognises in the sea one of the great features of the earth, and questions it daily -as to its present and its past. The present features of the sea include much of surpassing interest, but the questions which relate to its origin and early history are still more attractive. Some of these questions are likely to interest a voyager from Canada entering the Atlantic by one of its greatest tributaries, the St. Lawrence. In doing so, we approach the ocean not at a right angle, but along a line only slightly inclined to its western side, and we find ourselves in a broad estuary or trough, having on its north-western side rugged hills of old crystalline rocks, the Laurentian, ridged up in great folds or earth waves parallel to the river. On the south-east or right-hand side we have 1 Published in 1867. THE GREAT ICE AGE a lower barrier of earth waves composed of sedimentary rocks somewhat later in date, but still geologically very ancient. We are thus introduced to a remarkable feature of the west side of the North Atlantic, namely, that its border is made up of very old rocks folded into mountain ridges thrown up at an ancient period, and approximately parallel to the coast. The Lower St. Lawrence occupies a furrow between two of these ridges. Here, however, a more modern feature attracts our attention. The sides of the bounding hills are cut in a succession of terraces, rising one above another from the level of the sea to a height of 500 feet or more, capped with long ranges of the white houses and barns of the Canadian habitants, and furnishing level lines for the " concession roads " which run along the coast. These terraces are really old sea margins indicating the stages of the elevation of the land out of the sea immediately before the modern period. On these terraces, and in the clays and sands which form the plateaus extend- ing in some places in front of them, are sea shells of the same kinds with those now living in the Gulf of St. Lawrence, and occasionally we find bones of whales which have been stranded on the old beaches. These terraces are, of course, indications of change of level in very modern times. They show that in what we call the Pleistocene age the land was lower than at present, and we shall find that in the Lower St. Lawrence there is evidence of a depression extending to over 1,000 feet, carrying the sea far up the valley, so that sea shells are found in the clays as far up as Kingston and Ottawa, and stranded skeletons of whales as far west as Smith's Falls, in Ontario. If we examine the shores more minutely, we shall find all along the south coast a belt of boulders which are often as much as eight to ten feet in diameter, and consist largely of rocks found only in the hills of the northern coast, more THE GREAT ICE AGE 349 than thirty miles distant, from which they must have been drifted to their present position. This boulder belt, which extends from the lowest tide mark about fifty feet or more upward, is sometimes piled in ridges and sometimes flattened out into a rude pavement. It is a product of the modern field ice, which, attaining a great thickness in winter, has boulders frozen into its bottom, and floating up and down with the tide, deposits these on the shore. At Little Metis, two hundred miles below Quebec, where I have a summer residence, I have from year to year cleared a passage through the boulder belt for bathing and for launching boats, and nearly every spring I find that boulders have been thrown into the cleared space by the ice, while one can notice from year to year differences in the position of very large boulders. If we pass inland from the shore belt of boulders, we shall find similar appearances on the inland terraces at various heights, up to at least 400 feet. These are inland boulder belts belonging to old shores now elevated. Like the modern boulder belt these inland belts and patches consist partly of Laurentian rocks from the North Shore, partly of sandstones and conglomerates in place near to their present sites. In some places the stones are smaller than those of the present beach, in other places of gigantic size. These boulders lie not only on the bare rock striated in places with ice grooves pointing to the north-north-east ; but on the old till or boulder clay, which also abounds with boulders, and which is more ancient than the superficial boulder drift. Locally we find here and there masses of fossiliferous limestone which must have been derived from the high ground to the south of the St. Lawrence, and which have been borne northward either by drift ice or by local glaciers. If now we study the polished and scored surfaces of rocks in the St. Lawrence valley and the bounding hills, we shall find that while the former testify to a great movement of 35O THE GREAT ICE AGE ice and boulders up the river from the north-east, the latter show evident signs of the movement of locial glaciers down the valleys of the Laurentide hills to the south, and on the continuation of the Appalachians south of the river similar evidence of the movement of land ice to the north. Thus we have evidence of the combined action of local glaciers and floating ice. To add to all this, we can find on the flat tops of the hard sandstone boulders on the beach the scratches made by the ice of last winter, often in the same north-easterly direction with those of the Pleistocene time. In addition to the ice formed in winter in the St. Lawrence itself, the snow- clad hills of Greenland send down to the sea great glaciers, which in the bays and fiords of that inhospitable region form at their extremities huge cliffs of everlasting ice, and annually "calve," as the seamen say, or give off a great progeny of ice islands, which, slowly drifted to the southward by the arctic current, pass along the American coast, diffusing a cold and bleak atmosphere, until they melt in the warm waters of the Gulf Stream. Many of these bergs enter the Straits of Belle-Isle, for the Arctic current clings closely to the coast, and a part of it seems to be deflected into the Gulf of St. Lawrence through this passage, carrying with it many large bergs. The voyager passing through this strait in clear weather may see numbers of these ice islands glisten- ing in snowy whiteness, or showing deep green cliffs and pinnacles sometimes with layers of earthy matter and stones, or dotted with numerous sea birds, which rest upon them when gorged with the food afforded by shoals of fish and others marine animals which haunt these cold seas. In early summer the bergs are massive in form, often with flat tops, but as the summer advances they become eroded by the sun and warm winds, till they present the most grotesque forms of rude towers and spires rising from broad foundations little elevated above the water. THE GREAT ICE AGE 351 Mr. Vaughan, late superintendent of the Lighthouse at Belle-Isle, has kept a register of icebergs for several years. He states that for ten which enter the straits, fifty drift to the southward, and that most of those which enter pass inward on the north side of the island, drift toward the western end of the straits, and then pass out on the south side of the island, so that the straits seem to be merely a sort of eddy in the course of the bergs. The number in the straits varies much in differ- ent seasons of the year. The greatest number are seen in spring, especially in May and June ; and toward autumn and in the winter very few remain. Those which remain until autumn are reduced to mere skeletons ; but if they survive until winter, they again grow in dimensions, owing to the accu- mulations upon them of snow and new ice. Those that we saw early in July were large and massive in their proportions. The few that remained when we returned in September were smaller in size, and cut into fantastic and toppling pinnacles. Vaughan records that on the 3oth of May, 1858, he counted in the Straits of Belle-Isle 496 bergs, the least of them sixty feet in height, some of them half a mile long and 200 feet high. Only one-eighth of the volume of floating ice appears above water, and many of these great bergs may thus touch the ground in a depth of thirty fathoms or more, so that if we ima- gine four hundred of them moving up and down under the in- fluence of the current, oscillating slowly with the motion of the sea, and grinding on the rocks and stone-covered bottom at all depths from the centre of the channel, we may form some con- ception of the effects of these huge polishers of the sea floor. Of the bergs which pass outside of the straits, many ground on the banks off Belle-Isle. Vaughan has seen a hundred large bergs aground at one time on the banks, and they ground on various parts of the banks of Newfoundland, and all along the coast of that island. As they are borne by the deep-seated cold current, and are scarcely at all affected by the wind, they 352 THE GREAT ICE AGE move somewhat uniformly in a direction from north-east to south-west, and when they touch the bottom, the striation or grooving which they produce must be in that direction. In passing through the straits in July, I have seen great numbers of bergs, some low and flat-topped, with perpendicular sides, others convex or roof-shaped, like great tents pitched on the sea ; others rounded in outline or rising into towers and pinnacles. Most of them were of a pure dead white, like loaf sugar, shaded with pale bluish green in the great rents and recent fractures. One of them seemed as if it had grounded and then overturned, presenting a flat and scored surface covered with sand and earthy matter. At present we wish to regard the icebergs of Belle-Isle in their character of geological agents. Viewed in this aspect, they are in the first place parts of the cosmical arrangements for equalizing temperature, and for dispersing the great accu- mulations of ice in the Arctic regions, which might otherwise unsettle the climatic and even the static equilibrium of our globe, as they are believed by some imaginative physicists and geologists to have done in the so-called glacial period. If the ice islands in the Atlantic, like lumps of ice in a pitcher of water, chill our climate in spring, they are at the same time agents in preventing a still more serious secular chilling which might result from the growth without limit of the Arctic snow and ice. They are also constantly employed in wearing down the Arctic land, and aided by the great northern current from Davis's Straits, in scattering stones, boulders and sand over the banks along the American coast. Incidentally to this work, they smooth and level the higher parts of the sea bottom, and mark it with furrows and strire indicative of the direction of their own motion. When we examine a chart of the American coast, and observe the deep channel and hollow submarine valleys of the Arctic current, and the sandbanks which extend parallel to this THE GREAT ICE AGE 353 channel from the great bank of Newfoundland to Cape Cod, we cannot avoid the conclusion that the Arctic current and its ice have great power both of excavation and deposition. On the one hand, deep hollows are cut out where the current flows over the bottom, and on the other, great banks are heaped up where the ice thaws and the force of the current is abated. I have been much struck with the worn and abraded appear- ance of stones and dead shells taken up from the banks off the American coast, and am convinced that an erosive power com- parable to that of a river carrying sand over its bed, and mate- rially aided by the grinding action of ice, is constantly in action under the waters of the Arctic current. 1 The unequal pres- sure resulting from this deposition and abrasion is not improb- ably connected with the slight earthquakes experienced in Eastern America, and also with the slow depression of the coast ; and if we go back to that earliest of all geological periods when the Laurentian rocks of Sir Wm. Logan, consti- tuting the Labrador coast and the Laurentide Hills, were alone above water, we may even attribute in no small degree to the Arctic current of that old time the heaping up of those thou- sands of feet of deposits which now constitute the great range of the Alleghany and Aalachian mountains, and form the breast bone of the American continent. In those ancient times also large stones were floated southward, and enter into the composition of very old conglomerates. 1 At the time when this was written I had only studied stones brought up accidentally by fishermen and others from the banks of Newfoundland and elsewhere. At a later date Murray of the Challenger has given more ample material, He states that the bottom in the Labrador current, 100 miles from land, was found to be blue mud with 60 per cent, of sand and stones ; and mentions a block of syenite weighing 490 Ibs. taken up in 1,340 fathoms, and stones and pebbles of quartzite, limestone, dolomite, mica schist and serpentine, one of which was glaciated. This is the modern boulder clay produced by Greenland glaciers and the field ice of Baffin's Bay and the Labrador coast. 354 THE GREAT ICE AGE But such large speculations might soon carry us far from Belle-Isle, and to bring us back to the American coast and to the domain of common things, we may note that a vast variety of marine life exists in the cold waters of the Arctic current, and that this is one of the reasons of the great and valuable fisheries of Labrador, Newfoundland and Nova Scotia, regions in which the sea thus becomes the harvest field of much of the human population. On the Arctic current and its ice also floats to the southward the game of the sealers of St. John and the whalers of Gaspe. We may now proceed to connect these statements as to the distribution of icebergs, with the glaciated condition of our continents, with the remarkable fact that the same effects now produced by the ice and the Arctic current in the Strait of Belle-Isle and the deep-current channel off the American coast, are visible all over the North American and European land north of forty degrees of latitude, and that there is evidence that the St. Lawrence valley itself was once a gigantic Belle- Isle, in which thousands of bergs worked perhaps for thou- sands of years, grinding and striating its rocks, cutting out its deeper parts, and heaping up in it quantities 01 northern debris. Out of this fact of the so-called glaciated condition of the sur- face of our continents has, however, arisen one of the great controversies of modern geology. While all admit the action of ice in distributing and arranging the materials which consti- tute the last coating which has been laid upon the surface of our continents, some maintain that land glaciers have done the work, others, that sea-borne ice has been the main agent employed. As in some other controversies, the truth seems to lie between the extremes. Glaciers are slow, inactive, and limited in their sphere. Floating ice is locomotive and far- travelled, extending its action to great distances from its sources. So far, the advantages are in favour of the flotation. But the work which the glacier does is done thoroughly, and, THE GREAT ICE AGE 355 time and facilities being given, it may be done over wide areas. Again, the iceberg is the child of the glacier, and therefore the agency of the one is indirectly that of the other. Thus, in any view we must plough with both of these geological oxen, and the controversy becomes like that old one of the Neptunists and Plutonists, which has been settled by admitting both water and heat to have been instrumental in the formation of rocks. In the midst of these controversies a geologist resident in Great Britain or Canada should have some certain doctrine as to the question whether at that period, geologically recent, which we call the Pleistocene period, the land was raised to a great height above the sea, and covered like Greenland with a mantle of perpetual ice, or whether it was, like the strait of Belle-Isle and the banks of Newfoundland, under water, and annually ground over by icebergs, or whether, as now seems more probable, it was in part composed of elevated ridges covered with snow and sending down glaciers, and partly de- pressed under the level of ice-laden straits and seas. A great advocate of the glacier theory has said that we can- not properly appreciate his view without exploring thoroughly the present glaciers of Greenland and ascertaining their effects. This I have not had opportunity to do, but I have endeavoured to do the next best thing by passing as rapidly as possible from the icebergs of Belle-Isle to the glaciers of Mont Blanc, and by asking the question whether Canada was in the Pleistocene period like the present Belle-Isle or the present Mont Blanc, or whether it partook of the character of both ? and taking ad- vantage of these two most salient points in order to elicit a reply. Transporting ourselves, then, to the monarch of the Alps, let us suppose we stand upon the Flegere, a spur of the mountains fronting Mont Blanc, and commanding a view of the entire group. From this point the western end of the range presents the rounded summit of Mont Blanc proper, flanked by the s. E. 26 356 THE GREAT ICE AGE lower eminences of the Dome and Aiguille de Goute, which rise from a broad and uneven plateau of neve or hard snow, sending down to the plain two great glaciers or streams of ice, the Bossons and Tacony glaciers. Eastward of Mont Blanc the neve or snow plateau is penetrated by a series of sharp points of rock or aiguilles, which stretch along in a row of serried peaks, and then give place to a deep notch, through which flows the greatest of all the glaciers of this side of Mont Blanc, the celebrated Mer de Glace, directly in front of our standpoint. To the left of this is another mass of aiguilles, culminating in the Aiguille Verte. This second group of needles descends into the long and narrow Glacier of Argen- tiere, and beyond this we see in the distance the Glacier and Aiguille de Tour. As seen from this point, it is evident that the whole system of the Mont Blanc glaciers originates in a vast mantle of snow capping the ridge of the chain, and extend- ing about twenty miles in length, with a breadth of about five miles. This mass of snow being above the limits of perpetual frost, would go on increasing from year to year, except so far as it might be diminished by the fall of avalanches from its sides, were it not that its plasticity is sufficient to enable the frozen mass to glide slowly down the valleys, changing in its progress into an icy stream, which, descending to the plain, melts at its base and discharges itself in a torrent of white muddy water. The Mont Blanc chain sends forth about a dozen of large glaciers of this kind, besides many smaller ones. Crossing the valley of Chamouni, and ascending the Montan- vert to a height of about 6,000 feet, let us look more particu- larly at one of these glaciers, the Mer de Glace. It is a long valley with steep sides, about half a mile wide, and rilled with ice, which presents a general level or slightly inclined surface, traversed with innumerable transverse cracks or crevasses, penetrating apparently to the bottom of the glacier, and with slippery sloping edges of moist ice threatening at every step to THE GREAT ICE AGE 357 plunge the traveller into the depths below. Still the treacher- ous surface is daily crossed by parties of travellers, apparently without any accident. The whole of the ice is moving steadily along the slope on which it rests, at the rate of eight to ten inches daily the rate of motion is less in winter and greater in summer ; and farther down, where the glacier goes by the name of the Glacier du Bois, and descends a steeper slope, its rapid- ity is greater; and at the same time by the opening of immense crevasses its surface projects in fantastic ridges and pinnacles. The movements and changes in the ice of these glaciers are in truth very remarkable, and show a mobility and plasticity which at first sight we should not have been prepared to expect in a solid like ice. 1 The crevasses become open or closed, curved upwards or downwards, perpendicular or in- clined, according to the surface upon which the glacier is mov- ing, and the whole mass is crushed upward or flattens out, its particles evidently moving on each other with much the same result as would take place in a mass of thick mud similarly moving. On the surface of the ice there are a few boulders and many stones, and in places these accumulate in long irregular bands indicating the lines of junction of the minor ice streams coming in from above to join the main glacier. At the sides are two great mounds of rubbish, much higher than the present surface of the glacier. They are called the lateral moraines, and consist of boulders, stones, gravel and sand, confusedly intermingled, and for the most part retaining their sharp angles. This mass of rubbish is moved downward by the glacier, and with the stones constituting the central moraine, 1 I need scarcely say that I adopt the explanation of glacier motion given by Forbes. "The fuller consideration of the physical properties of glacier ice leads essentially to the same conclusions as those to which Forbes was led forty-one years ago by the study of the larger phenomena of glacier motion, that is, that the motion is that of a slightly viscous mass, partly sliding upon its bed, partly shearingupon itself under the influence of gravity." Trotter, Proc. Royal Society of London, xxxviii. 107. 358 THE GREAT ICE AGE is discharged at the lower end, accumulating there in the mass of detritus known as the terminal moraine. Glaciers have been termed rivers of ice ; but there is one respect in which they differ remarkably from rivers. They are broad above and narrow below, or rather, their width above corresponds to the drainage area of a river. This is well seen in a map of the Mer de Glace. From its termination in the Glacier du Bois to the top of the Mer de Glace proper, a dis- tance of about three and a half miles, its breadth does not ex- ceed half a mile, but above this point it spreads out into three great glaciers, the Geant, the Du Chaud, and the Talefre, the aggregate width of which is six or seven miles. The snow and ice of a large interior tableland or series of wide valleys are thus emptied into one narrow ravine, and pour their whole accumulations through the Mer de Glace. Leaving, however, the many interesting phenomena connected with the motion of glaciers, and which have been so well interpreted by Saussure, Agassiz, Forbes, Hopkins, Tyndall, and others, we may con- sider their effects on the mountain valleys in which they operate. 1. They carry quantities of dkbris from the hill tops and mountain valleys downward into the plains. From every peak, cliff and ridge the frost and thaw are constantly loosening stones and other matters which are swept by avalanches to the surface of the glacier, and constitute lateral moraines. When two or more glaciers unite into one, these become medial moraines, and at length are spread over and through the whole mass of the ice. Eventually all this material, including stones of immense size, as well as fine sand and mud, is deposited in the terminal moraine, or carried off by the streams. 2. They are mills for grinding and triturating rock. The pieces of rock in the moraine are, in the course of their move- ment, crushed against one another and the sides of the valley, and are cracked and ground as if in a crushing mill. Further THE GREAT ICE AGE 359 the stones on the surface of the glacier are ever falling into crevasses, and thus reach the bottom of the ice, where they are further ground one against another and the floor of rock. In the movement of the glacier these stones seem in some cases to come again to the surface, and their remains are finally dis- charged in the terminal moraine, which is the waste heap of this great mill. The fine material which has been produced, the flour of the mill, so to speak, becomes diffused in the water which is constantly flowing from beneath the glacier, and for this reason all the streams flowing from glaciers are turbid with whitish sand and mud. ' The Arve, which drains the glaciers of the north side of Mont Blanc, carries its burden of mud into the Rhone, which sweeps it, with the similar material of many other Alpine streams, into the Mediterranean, to aid in filling up the bottom of that sea, whose blue waters it discolours for miles from the shore, and to increase its own ever-enlarging delta, which encroaches on the sea at the rate of about half a mile per century. The upper waters of the Rhone, laden with similar material, are filling up the Lake of Geneva; and the great deposit of " loess " in the alluvial plain of the Rhine, about which Gaul and German have contended since the dawn of European history, is of similar origin. The mass of material which has thus been carried off from the Alps, would suffice to build up a great mountain chain. Thus, by the action of ice and water "The mountain falling comelh to naught, And the rock is removed out of its place." Many observers who have commented on these facts have taken it for granted that the mud thus sent off from glaciers, and which is so much greater in amount than the matter remaining in their moraines, must be ground from the bottom of the glacier valleys, and hence have attributed to these 360 THE GREAT ICE AGE glaciers great power of cutting out and deepening their valleys. But this is evidently an error, just as it would be an error to suppose the flour of a grist mill ground out of the mill stones. Glaciers, it is true, groove and striate and polish the rocks over which they move, and especially those of projecting points and slight elevations in their beds ; but the material which they grind up is principally derived from the. exposed frost-bitten rocks above them, and the rocky floor under the glacier is merely the nether mill stone against which those loose stones are crushed. The glaciers, in short, can scarcely be regarded as cutting agents at all, in so far as the sides and bottoms of their beds are concerned, and in the valleys which the old glaciers have abandoned, it is evident that the torrents which have succeeded them have far greater cutting power. The glaciers have their'periods of advance and of recession. A series of wet and cool summers causes them to advance and encroach on the plains, pushing before them their moraines, and even forests and human habitations. In dry and warm summers they shrink and recede. Such changes seem to have occurred in bygone times on a gigantic scale. All the valleys below the present glaciers present traces of former glacier action. Even the Jura mountains seem at one time to have had glaciers. Large blocks from the Alps have been carried across the intervening valley and lodged at great heights on the slopes of the Jura, leading the majority of the Swiss and Italian geologists to believe that even this great valley and the basin of Lake Leman were once filled with glacier ice. But, unless we can suppose that the Alps were then vastly higher than at present, this seems scarcely to be physically possible, and it seems more likely that the conditions were just the reverse of those supposed, namely, that the low land was sub- merged, and that the valley of Lake Leman was a strait like Belle-Isle, traversed by powerful currents and receiving ice- bergs from both Jurassic and Alpine glaciers, and probably THE GREAT ICE AGE 361 from farther north. One or other supposition is required to account for the appearances, which may be explained on either view. The European hills may have been higher and colder, and changes of level elsewhere may have combined with this to give a cold climate with moisture; or a great submergence may have left the hills as islands, and may have so reduced the temperature by the influx of arctic currents and ice, as to enable the Alpine glaciers to descend to the level of the sea. Now, we have evidence of such submergence in the beds of sea-shells and travelled boulders scattered over Europe, while we also have evidence of contemporaneous glaciers, in their traces on the hills of Wales and Scotland and elsewhere, where they do not now occur. I have long maintained that in America all the observed facts imply a climate no colder than that which would have resulted from the subsidence which we know to have occurred in the temperate latitudes in the Pleistocene period, and though I would not desire to speak so positively about Europe, I confess to a strong impression that the same is the case there, and that the casing of glacier ice imagined by many geologists, as well as the various hypotheses which have been devised to account for it, and to avoid the mechanical, meteorological, and astronomical difficulties attending it, are alike gratuitous and chimerical, as not being at all required to account for observed facts, and being contradictory, when carefully considered, to known physical laws as well as geological phenomena. 1 Carrying with me a knowledge of the phenomena of the glacial drift as they exist in North America, and of the modern ice drift on its shores, I was continually asking myself the question To what extent do the phenomena of glacier drift and erosion resemble these ? and standing on the moraine of the Bosson glacier, which struck me as more like boulder clay 1 Canadian Naturalist, vols. viii. and ix. Geological Magazine, Decem- ber, 1865. 362 THE GREAT ICE AGE than anything else I saw in the Alps, with the exception of some recent avalanches, I jotted down what appeared to me to be the most important points of difference. They stand thus : 1. Glaciers heap up their debris in abrupt ridges. Floating ice sometimes does this, but more usually spreads its load in a more or less uniform sheet. 1 2. The material of moraines is all local. Floating ice carries its deposits often to great distances from their sources. 3. The stones carried by glaciers are mostly angular, except where they have been acted on by torrents. Those moved by floating ice are more often rounded, being acted on by the waves and by the abrading action of sand drifted by cur- rents. 4. In the marine glacial deposits mud is mixed with stones and boulders. In the case of land glaciers, most of this mud is carried off by streams and deposited elsewhere. 5. The deposits from floating ice may contain marine shells. Those of glaciers cannot, except where, as in Greenland and Spitzbergen, glaciers push their moraines out into the sea. 6. It is of the nature of glaciers to flow in the deepest ravines they can find, and such ravines drain the ice of exten- sive areas of mountain land. Floating ice, on the contrary, acts with greatest ease on flat surfaces or slight elevations in the sea bottom. . 7. Glaciers must descend slopes and must be backed by large supplies of perennial snow. Floating ice acts indepen- dently, and being water-borne may work up slopes and on level surfaces. 8. Glaciers striate the sides and bottoms of their ravines very unequally, acting with great force and effect only on those places where their weight impinges most heavily. Float- 1 Under floating ice I include floe, pack, and bordage ice as well as .bergs. THE GREAT ICE AGE 363 Ing ice, on the contrary, being carried by constant currents and over comparatively flat surfaces, must striate and grind more regularly over large areas, and with less reference to local inequalities of surface. 9. The direction of the striae and grooves produced by glaciers depends on the direction of valleys. That of floating ice, on the contrary, depends upon the direction of marine currents, which is not determined by the outline of the surface, but is influenced by the large and wide depressions of the sea bottom. 10. When subsidence of the land is in progress, floating ice may carry boulders from lower to higher levels. Glaciers cannot do this under any circumstances, though in their pro- gress they may leave blocks perched on the tops of peaks and ridges. I believe that in all these points of difference the boulder clay and drift on the lower lands of Canada and other parts of North America, correspond rather with the action of floating ice than of land ice; though certainly with glaciers on such land as existed at the different stages of the submergence, and these glaciers drifting stones and earthy matter in different directions from higher land toward the sea. More especially is this the case in the character of the striated surfaces, the bedded dis- tribution of the deposits, the transport of material up the natural slope, the presence of marine shells, and the mechanical and chemical characters of the boulder clay. In short, those who regard the Canadian boulder clay as a glacier deposit, can only do so by overlooking essential points of difference between it and modern accumulations of this kind. I would wish it here to be distinctly understood, that I do not doubt that at the time of the greatest Pleistocene submerg- ence of Eastern America, at which time I believe the greater part of the boulder clay was formed, and the more important striation effected, the higher hills then standing as islands would 364 THE GREAT ICE AGE be capped with perpetual snow, and through a great part of the year surrounded with heavy field and barrier ice, and that in those hills there might be glaciers of greater or less extent. Further, it should be understood that I regard the boulder clays of the St. Lawrence valley as of different ages, ranging from those of the early Pleistocene to that now forming in the Gulf of St. Lawrence; and that during these periods great changes of level occurred. Further, that this boulder clay shows in every place where I have been able to examine it, evidence of subaqueous accumulation, in the presence of marine shells or in the unweathered state of the rocks and minerals enclosed in it; conditions which, in my view, preclude any reference of it to glacier action, except possibly in some cases to that of glaciers stretching from the land over the mar- gin of the sea, and forming under water a deposit equivalent in character to the boue gladare of the bottom of the Swiss glaciers. But such a deposit must have been local, and would not be easily distinguishable from the marine boulder clay. It is of some interest to compare Canadian deposits with those of Scotland, 1 which in character and relations so closely resemble those of Canada ; but I confess several of the facts lead me to infer that much of what has been regarded as of subaerial origin in that country must really be marine, though whether deposited by icebergs or by the fronts of glaciers terminating in the sea, I do not pretend to determine. 2 It must, howeve", be observed that the antecedent probability of a glaciated con- dition is much greater in the case of Scotland than in that of Canada, from the high northern latitude of the former, its hilly and maritime character, and the fact that its present 1 Journal of Geological Society. Papers by Jamieson, Bryce, Crosskey, and Geikie. a Geikie, Trans. Royal Society of Edin. Geikie assigns a more compli- cated structure than appears to be present in Canada; but there are Cana- dian equivalents of the principal glacial periods which he assumes, THE GREAT ICE AGE 365 exemption from glaciers is due to what may be termed excep- tional and accidental geographical conditions ; more especially to the distribution of the waters of the Gulf Stream, which might be changed by a comparatively small subsidence in Cen- tral America. To assume the former existence of glaciers in a country in north latitude 56, and with its highest hills, under the present exceptionally favourable conditions, snow-capped during most of the year, is a very different thing from assuming a covering of continental ice over wide plains more than ten degrees farther south, and in which, even under very unfavour- able geographical accidents, no snow can endure the summer sun, even in mountains several thousand feet high. Were the plains of North America submerged and invaded by the cold arctic currents, the Gulf Stream being at the same time turned into the Pacific, the temperature of the remaining North American land would be greatly diminished ; but under these circumstances the climate of Scotland would necessarily be reduced to the same condition with that of South Greenland or Northern Labrador. As we know such a submergence of America to have occurred in the Pleistocene period, it does not seem necessary to have recourse to any other cause for either side of the Atlantic. It would, however, be a very interesting point to determine, whether in the Pleistocene period the greatest submergence of America coincided with the greatest submergence of Europe, or otherwise. It is quite possible that more accurate information on this point might remove some present difficulties. I think it much to be desired that the many able observers now engaged on the Pleistocene ot Europe, would at least keep before their minds the probable effects of the geographical conditions above referred to, and inquire whether a due consideration of these would not allow them to dispense altogether with the somewhat extravagant theories of glaciation now agitated. The preceding pages give the substance of my conclusions 366 THE GREAT ICE AGE of twenty-four years ago. I give those of to-day from a paper of 1 89 1, 1 relating to Eastern Canada only : These conclusions have, in my judgment, been confirmed, and their bearing extended, more especially by the researches of Mr. Chalmers, who has shown in the most convincing way that glaciers proceeding from local centres along with sea-borne ice, may have been the agents in glaciating surfaces and trans- porting boulders in Nova Scotia and New Brunswick. Taken in connection with the observations of Dr. Dawson and Mr. McConnell in the Cordillera region of the west, and those of Dr. Bell, Dr. Ells, Mr. Low, and others in the Laurentian country north of the St. Lawrence, and in the Province of Quebec, we may now be said to know that there was not, even at the height of the glacial refrigeration of America, a contin- ental ice sheet, but rather several distinct centres of ice action, one in the Cordillera of the West, one on the Laurentian V-shaped axis, and one on the Appalachians, with subordinate centres on isolated masses like the Adirondacks, and at certain periods even on minor hills like those of Nova Scotia. It would further seem that, in the west at least, elevation of the mountain ridges coincided with depression of the plains. In Newfoundland also, it would appear from the observations of Captain Kerr, with which those of Mr. Murray are in har- mony, 8 though they have been differently interpreted, that the gathering ground of ice was in the interior of the island, and that glaciers moved thence to the coasts, but principally to the east coast, as was natural from the conformation of the land and the greater supply of moisture from the Atlantic. The labours of Murray in Newfoundland, of Matthew, Chalmers, Bailey, and others, in Nova Scotia and New Bruns- wick, have considerably enlarged our knowledge of Pleistocene fossils, showing, however, that the marine fauna is the same 1 Supplement to 4th edition of "Acadian Geology," 1891. 2 Trans. Royal Society of Canada, vol. i. THE GREAT ICE AGE 367 with that of the beds of like age in the St. Lawrence valley, and with the existing fauna of the Labrador coast and colder por- tions of the Gulf and River St. Lawrence, as ascertained by Prickard, Whiteaves, and the writer. It would seem that throughout this region, the 60 feet and the 600 feet terraces were the most important with reference to these marine remains, and that their chief repository is in the Upper Leda Clay, a marine deposit intermediate between the Lower and Upper boulder drift, and corresponding to the interglacial beds of the interior of America. The general conditions of the period may be thus sum- marized : In this district, and the eastern part of North America generally, it is, I think, universally admitted that the later Pliocene period was one of continental elevation, and probably of temperate climate. The evidence of this is too well known to require re-statement here. It is also evident, from the raised beaches holding marine shells, extending to elevations of 600 feet, and from drift boulders reaching to a far greater height, that extensive submergence occurred in the middle and later Pleistocene. This was the age of the beds I have named the Leda clays and Saxicava sands, found at heights of 600 feet above the sea in the St. Lawrence valley, nearly as far west as Lake Ontario. It is reasonable to conclude that the till or boulder clay, under the Leda clay, belongs to the earliest period of prob- ably gradual subsidence, accompanied with a severe climate, and with snow and glaciers on all the higher grounds, sending glaciated stones into the sea. This deduction agrees with the marine shells, polyzoa, and cirripedes found in the boulder deposits on the lower St. Lawrence, with the unoxidized charac- ter of the mass, which proves subaqueous deposition, with the fact that it contains soft-boulders, which would have crumbled if exposed to the air, with its limitation to the lower levels and 368 THE GREAT ICE AGE absence on the hillsides, and with the prevalent direction of striation and boulder drift from the north-east. 1 All these indications coincide with the conditions of the modern boulder drift on the lower St. Lawrence and in the Arctic regions, where the great belts and ridges of boulders accumulated by the coast ice would, if the coast were sinking, climb upward and be filled in with mud, forming a continuous sheet of boulder deposit similar to that which has accumulated and is accumulating on the shores of Smith's Sound and else- where in the Arctic, and which, like the older boulder clay, is known to contain both marine shells and driftwood. 2 The conditions of the deposit of "till" diminished in intensity as the subsidence continued. The gathering ground of local glaciers was lessened, the ice was no longer limited to narrow sounds, but had a wider scope, as well as a freer drift to the southward, and the climate seems to have been improved. The clays deposited had few boulders and many marine shells, and to the west and north there were land-producing plants akin to those of the temperate regions; and in places only slightly elevated above the water, peaty deposits accumulated. The shells of the Leda clay indicate depths of less than 100 fathoms. The numerous Foraminifera, so far as have been observed, belong to this range, and I have never seen in this clay the assemblage of foraminiferal forms now dredged from 200 to 300 fathoms in the Gulf of St. Lawrence. I infer that the subsidence of the Leda clay period and of the interglacial beds of Ontario belongs to the time of the sea beaches from 450 to 600 feet in height, which are so marked and extensive as to indicate a period of repose. In this period 1 Notes on the Post-Pliocene : Canadian Naturalist, op. cit. ; also Paper by the author on Boulder Drift at Metis, Canadian Record of Science, vol. ii., 1 886, p. 36, et seq. 2 For references see " Royal Society's Arctic Manual," London, 1875, op. cit. THE GREAT ICE AGE 369 there were marine conditions in the lower and middle St. Lawrence and in the Ottawa valley, and swamps and lakes on the upper Ottawa and the western end of Lake Ontario. It is quite probable, nay, certain, that during this interglacial period re-elevation had set in, since the upper Leda clay and the Saxicava sand indicate shallowing water, and during this re- elevation the plant-covered surface would extend to lower levels. This, however, must have been followed by a second subsi- dence, since the water-worn gravels and loose, far-travelled boulders of the later drift rose to heights never reached by the till or the Leda clay, and attained to the tops of the highest hills of the St. Lawrence valley, 1,200 feet in height, and else- where to still greater elevations. This second boulder drift must have been wholly marine, and probably not of long duration. It shows no evidence of colder climate than that now prevalent, nor of extensive glaciers on the mountains ; and it was followed by a paroxysmal elevation in successive stages till the land attained even more than its present height, as subsidence is known to have been proceeding in modern times. I am quite aware that the above sequence and the causes assumed are somewhat different from those held by many geologists with reference to regions south of Canada ; but must hold that they are the only rational conclusions which can be propounded with reference to the facts observed from the parallel of 45 to the Arctic Ocean. My own observations have been chiefly in the eastern part of North America. My son, Dr. G. M. Dawson, has much more ably and thoroughly explored those of the west ; and after describing the immense Cordilleran ice mass which ex- tended for a length of 1,200 miles along the mountains of British Columbia and discharged large glaciers to the north, as well as to the west and south, and stating his reasons for believing in that differential elevation and depression which 3/0 THE GREAT ICE AGE caused the greatest height of the mountains to coincide with the greatest depression of the plains, and vica versa, and show- ing the Cordilleran glacier must have been separated by a water area from that of the Laurentide hills on the east, thus concludes : " It is now distinctly known, as the result of work done under the auspices of the Geological Survey of Canada, and more particularly of observations by the writer and his col- leagues, Messrs. McConnel and Tyrrell, that the extreme margins of the western and eastern glaciated areas of the continent barely overlap, and then only to a very limited extent, while the two great centres of dispersion were entirely distinct. For numerous reasons which cannot be here entered into, the writer does not consider it probable, or even possible, that the great confluent glacier of the north-eastern part of the continent extended at any time far into the area of the great plains ; but erratics and drift derived from this ice mass did so extend, and are found between the 49th and 5oth parallels, stranded on the surface of moraines produced by the large local glaciers of the Rocky Mountains. Recognising, however, the essential separateness of the western and eastern confluent ice masses, and the fact that it is no longer appropriate to desig- nate one of these the " continental glacier," the writer ventures to propose that the eastern mer de glace may appropriately be named the great Laurentide glacier, while its western fellow is known as the " Cordilleran glacier." It may be added that there is good evidence to show that both the Laurentide and Cordilleran glaciers discharged into open water to the north." These conclusions, based on a large induction of facts applying to a very large area of the North American Continent, coincide with my own observations in the east, and with the inferences deducible from the present condition of Greenland and Arctic America. When extreme glacialists point to Greenland and ask us to THE GREAT ICE AGE 371 believe that in the Glacial age the whole continent of North America, as far south as the latitude of 40, was covered with a continuous glacier, having a wide front, and thousands of feet thick, we may well ask, first, what evidence there is that Green- land or even the Antarctic continent is at present in such a condition ; and, secondly, whether there exists a possibility that the interior of a great continent could ever receive so large an amount of precipitation as that required. So far as present knowledge exists, it is certain that the meteorologist and the physicist must answer both questions in the negative. In short, perpetual snow and glaciers must be local, and cannot be con- tinental, because of the vast amount of evaporation and con- densation required. These can only be possible where com- paratively warm seas supply moisture to cold and elevated land, and this supply cannot, in the nature of things, penetrate far inland. The actual condition of interior Asia and interior America in the higher northern latitudes affords positive proof of this. In a state of partial submergence of our northern continents, we can readily imagine glaciation by the combined action of local glaciers and great ice floes ; but in whatever way the phenomena of the boulder clay and of the so-called " terminal moraines " are to be accounted for, the theory of a continuous continental glacier must be given up. The great interior plain of western Canada, between the Laurentian axis on the east and the Rocky Mountains on the west, is seven hundred miles in breadth, and is covered with glacial drift, presenting one of the greatest examples of this deposit in the world. Proceeding eastward from the base of the Rocky Mountains, the surface, at first more than 4,000 feet above the sea level, descends by successive steps to 2,500 feet, and is based on Cretaceous and Laramie rocks, covered with boulder clay and sand, in some places from one hundred to two hundred feet in depth, and filling up pre-existing hollows, though itself sometimes piled into ridges. Near the Rocky s. E. 27 3/2 THE GREAT ICE AGE Mountains the bottom of the drift consists of --gravel not glaciated. This extends to about one hundred miles east of the mountains, and must have been swept by water out of their valleys. The boulder clay resting on this deposit is largely 'made up of local debris , in so far as its paste is concerned. It contains many glaciated boulders and stones from the Lauren- tian region to the east, and also smaller pebbles from the Rocky Mountains, so that at the time of its formation there must have been driftage of large stones for seven hundred miles or more from the east, and of smaller stones from a less distance on the west. The former kind of material extends to the base of the mountains, and to a height of more than 4,000 feet. One boulder is mentioned as being 42 x 40 x 20 feet in dimensions. The highest Laurentian boulders seen were at an elevation of 4,660 feet on the base of the Rocky Mountains. The boulder clay, when thick, can be seen to be rudely strati- fied, and at one place includes beds of laminated clay with compressed peat, similar to the forest beds described by Worthen and Andrews in Illinois, and the so-called interglacial beds described by Hinde on Lake Ontario. The leaf beds on the Ottawa " river, and the drift trunks found in the boulder clay of Manitoba, belong to the same category, and indicate in the midst of the Glacial period many forest oases far to the north, having a temperate rather than an arctic flora. In the valleys of the Rocky Mountains opening on these plains there are evidences of large local glaciers now extinct, and similar evidences exist on the Laurentian highlands on the east. A recent paper of Dr. G. M. Dawson on the Palaeography of the Rocky Mountains illustrates in a most convincing manner the changes which have occurred in the Cordillera of North America, and the differential elevation and depression which have affected its climate in the later geological periods. 1 Perhaps the most remarkable feature of the western drift region 1 Transactions Royal Society of Canada, 1890. THE GREAT ICE AGE 373 is that immense series of ridges of drift piled against an escarp- ment of Laramie and Cretaceous rocks, at an elevation of about 2,500 feet, and known as the " Missouri Coteau." It is in some places 30 miles broad and 180 feet in height above the plain at its foot, and extends north and south for a great distance : being, in fact, the northern extension of those great ridges of drift which have been traced south of the great lakes, and through Pennsylvania and New Jersey, and which figure on the geological maps as the edge of the continental glacier an explanation obviously inapplicable in those western regions where they attain their greatest development. It is plain that in the north it marks the western limit of the deep water of a glacial sea, which at some periods extended much farther west, perhaps with a greater proportionate depression in going westward, and on which heavy ice from the Laurentian dis- tricts on the east was wafted southwestward by the arctic currents, while lighter ice from the Rocky Mountains was being borne eastward from these mountains by the prevailing westerly winds. We thus have in the west, on a very wide scale, the same phenomena of varying submergence, cold cur- rents, great ice floes and local glaciers producing icebergs, to which I have attributed the boulder clay and upper boulder drift of eastern Canada. In short, we arrive at the conclusion that there never has been a continental glacier, properly so called, but that in the extreme Glacial period there have been great centres of snow and glacial action, in the Cordillera of the west, in the Laurentian plateau of the north, and in the northern Appalachians, and the Adirondacks, while the lower lands have been either submerged, or enjoying a climate habit- able by hardy animals and plants. The till or boulder clay has been called a "ground moraine," but there are really no Alpine moraines at all corresponding to it. On the other hand, it is more or less stratified, often rests on soft materials which glaciers would have swept away, some 374 THE GREAT ICE AGE times contains marine shells, or passes into marine clays in its horizontal extension, and invariably in its embedded boulders and its paste, shows an unoxidized condition, which could not have existed if it had been a subaerial deposit. When the Canadian till is excavated and exposed to the air, it assumes a brown colour, owing to oxidation of its iron, and many of its stones and boulders break up and disintegrate under the action of air and frost. These are unequivocal signs of a subaqueous deposit. Here and there we find associated with it, and es- pecially near the bottom and at the top, indications of power- ful water action, as if of land torrents acting at particular elevations of the land, or heavy surf and ice action on coasts, and the attempts to explain these by glacial streams have been far from successful. A singular objection sometimes raised against the subaqueous origin of the till is its general want of marine remains ; but this is by no means universal, and it is well known that coarse conglomerates of all ages are generally destitute of fossils, except in their pebbles, and it is further to be observed that the conditions of an ice-laden sea are not those most favourable for the extension of marine life, and that the period of time covered by the glacial age must have been short, compared with that represented by some of the older formations. It follows from all this that the great " continental moraine," which the United States Geological Survey has now "delineated for several thousand miles extending from the Atlantic to the Pacific," cannot be a glacier moraine, but must be, like its great continuation northward, the Missouri coteau, a margin of sea drift, and that we must explain the whole of the drift of the American continent by the supposition, first, of a period of elevation of the hills and subsidence of the valleys in which there were great accumulations of snow on the Western Cor- dillera ; the Laurentian axis, and the Appalachians and Adiron- dacks radiating in every direction from these points, while THE GREAT ICE AGE 375 minor areas of radiation may have temporarily existed on smaller elevations : that this was followed by a period of more equal level, in which parts of the low grounds were clothed with a temperate flora, the " Interglacial period " so called, succeeded by a second great depression, in which the high level boulders of the second boulder drift were wafted to great dis- tances by floating ice. The late Prof. Alexander Winchell, a man who did not hesitate to express his convictions, thus bears similar testi- mony : " There has been no continental glacier. There has been no uniform southerly movement of glacier masses. There has been no persistent declivity as a sine qua non, down which glacier movements have taken place. The continuity of the supposed continental glacier was interrupted in the regions of the dry and treeless plains of the west ; and in the interior and Pacific belts of the continent within the United States, ancient glaciation was restricted to the elevated slopes. ' J1 He might have added that the St. Lawrence valley was submerged and received the ends of Appalachian and Adirondack glaciers on the south-east, and those of Laurentide glaciers on the north-west. My friend Prof. Claypole, who, however, has some hesitation, fearing, I persume, to be cast out of the synagogue for heresy, ventures to say, 2 " We deduce from the facts and arguments stated above, that all the observations of glacial action in the northern hemisphere are explicable by assuming the existence of enormous and confluent 3 glacier-systems in and about the high lands of Europe, Asia, and America, which high lands be- came, therefore, glacial radiants, and shed their load of ice in all directions over the lower adjacent ground, along the lines of 1 Nov., 1890. 2 American Geologist, Feb., 1889. 3 The term "confluent "is not necessary here. The glaciers of all mountain chains may be said to be more or less confluent in the neve, from which individual glaciers radiate. 376 THE GREAT ICE AGE easiest flow ; that this theory does no violence to the analogy of the existing order of things, requiring merely an enlargement of actual glaciers by the intensification of actual conditions : that abundant evidence can he obtained, as, for example, from Switzerland, that the present glacier system of the earth was once of sufficient magnitude to produce all the observed phenomena ; that the most important glacial radiants in the northern hemisphere were, in North America, the district round Hudson Bay, New England and the Adirondacks, with certain areas in the western Cordilleras, and in Europe the Norwegian Dovrefelds and the Alps, Asia apparently possess- ing none of commensurate importance ; that it satisfactorily explains, also, the previously puzzling absence of glacial action over the great plain of Siberia, the coldest portion of the northern temperate zone ; that the belief in a vast polar ice cap, thousands of feet thick, covering the whole Arctic region, and extending almost continuously down to low latitudes, is an as- sumption doing violence to observed physical facts and to probability, that it is not required to account for the pheno- mena, and is, in fact, contradictory to some of them." In Europe there is equally good evidence of the existence of huge glaciers on the Scandinavian mountains and the Alps, and of lesser accumulations of ice on the hills, as, for instance, those of the British Islands ; but the Scandinavian boulders scattered over the plains of Great Britain must have been water borne. 1 In connection with these extracts I would observe that the writer, and those with whom he has acted in this matter, have never held that icebergs alone, or fields of ice alone, have pro- duced the Pleistocene deposits. Their contention has been that the period was one in which glaciers, icebergs, and field 1 The reports of the Scottish boulder committee, and Lapworth's recent careful examination of the deposits on the East of England (Jonrn. Geol. So(. t Aug., 1891), strongly confirm me in this opinion, THE GREAT ICE AGE 377 ice acted together, and along with aqueous agencies, in produc- ing the complicated formations of this remarkable age. They have, however, objected strenuously to the sole employment of one agent to the exclusion of others, and to attributing to that agent powers and extension which obviously could not belong to it, under the known laws which regulate the movement of glaciers by the force of gravity, and the precipitation of moisture in the form of snow on mountains and plateaus. These laws show that the movement of glaciers over level surfaces, or against the slope of the ground, and their moving stones otherwise than down slopes, are physical impossibilities, and that the accumulation of snow to form glaciers can take place only on elevated and cold land, supplied with large quantities of vapour from neighbouring water. Such accumu- lation can under no imaginable conditions take place in the interior plains and table lands of great continents. Applying these laws and conclusions to the whole northern hemisphere, we learn that the conditions to produce a glacial period are the diversion of the warm currents from the northern seas, the submergence of land in the temperate regions, and its invasion by cold Arctic water, and great condensation of snow on the higher lands. Whether this condensation has a tendency finally to rectify the state of affairs, by pressing down the mountains and elevating the plains, we do not know, but I should imagine that it has not ; for the high lands will, in the case supposed, be lightened by denudation, while the plains will be burdened with a great weight of deposit. Perhaps we should rather look to this as the agency for depressing and sub- merging the plains and elevating the hills, and suppose some other and more general pressure proceeding from the great sea basins, to effect the re-elevation of the plains. These questions suggest that of the date of the Glacial period. This subject has recently been discussed by Prestwich and others, with the result that there is no purely geological ground 378 THE GREAT ICE AGE for referring the Glacial age to a period so remote as that advo- cated by Croll on astronomical grounds. Claypole has recently discussed the matter at some length, and in a temperate spirit. 1 He takes the rate of erosion of the Niagara gorge as a measure, and shows that the Falls of St. Anthony, as described by Win- chell, and all the other falls and river gorges in North America, give similar estimates, which are confirmed by the evidences of lake ridges, of the rate of erosion, and of the conditions of animal and plant life. The whole go to show that the culmina- tion of the Glacial age may have occurred less than 10,000 years ago. He further shows that the differential elevation of Lakes Erie and Ontario, the greater ease with which the river could cut the lower part of its ravine, the probability that the part of the gorge between the whirlpool and the fall was not cut, but only cleaned out in modern times, and the possible greater flow of water in the early modern period, all tend to shorten the time required, and that, as Prestwich has inferred from other data, and the writer also in various papers, some of them of old date, the so-called post-glacial period, that of the melting away of the ice, may come within 8,000 to 10,000 years of our own time. Probably the first of these figures is the nearest to the truth, 2 so that, geologically considered, the Glacial age is very recent. Still another question of great cosmic interest relates to the possible alternation of glacial conditions in the northern and southern hemispheres. There is evidence of drift in the south- ern part of South America, similar to that in the north ; but was it deposited at the same time ? If we could be sure that it was not, many difficulties would be removed. The southern hemi- 1 Trans. Edinburgh Geol. Soc., vol. v., 1888. 2 Upham, one of the ablest and most experienced of the Glacial geolo- gists in the United States, in a recent paper on the causes of the glacial period, states similar conclusions, and adduces the evidence of Gilbert, Andrews, Wright, Emerson and others in the same sense. THE GREAT ICE AGE 379 sphere is at present emphatically the ocean hemisphere ; the northern, the land hemisphere. Perhaps these conditions may be capable of being reversed, in which case the periods of de- pression in the south may have corresponded with those of elevation in the north. One thing which we know is, that there is a polar ice ring, not an ice cap, for we do not know what is within its edges at the South Pole, about 2,000 miles in diameter, and this in the only circumstances in which it can exist, namely, surrounded by a vast ocean furnishing it with abundant aqueous vapour. We also know that from this ice ring radiate glaciers, carrying debris, with which the sea bottom is strown half way to the equator. If continents were elevated out of the Southern Ocean, we should probably have on their surfaces glacial deposits more widespread and continuous than any remaining on the continents of the northern hemisphere, and like some of them thinning out to a terminal edge or border, instead of a terminal moraine like that of a glacier. 1 Thus we may say with some truth that the southern hemisphere is now passing through one phase of the Glacial period. I have often thought that in the southern hemisphere the condition of Kerguelen Island and Heard Island, as described in the reports of the Challenger? must very nearly represent the state of some mountain ranges and peaks in North America in the Glacial age. Heard Island, in S. latitude 53 2', is a mountain peak 6,000 feet high, and 25 miles in length. It sends down large glaciers to the sea. In its larger neighbour, Kerguelen, the glaciers do not reach the sea ; but there is evi- dence that at one time they did. It is still more curious that, in Kerguelen the modern ice overlies late tertiary deposits, holding remains of large trees, indicating a more continental condition and mild climate at no very remote period. 1 This is now admitted by Chamberlain and others to be the case with the oldest boulder clay on the American continent. 2 Vol. i. p. 370, etc. 380 THE GREAT ICE AGE The glaciers of Heard Island and Kerguelen have, no doubt, been carrying down moraine material into the sea, and this is certainly done on a still greater scale by those of the Antarctic continent. This sends off bergs which fill the whole ocean south of 60, and float much farther north. Some of them have been seen 2,000 feet long and 200 high, and though most of the boulders they contain are necessarily concealed, yet masses of rock, supposed to weigh many tons, have been seen on them. The whole sea bottom off this continent, as far south as 64, consists of blue mud, with boulders and pebbles, some of them glaciated, and farther north there is, as far as 47 degrees of latitude, a considerable percentage of drift material, and this sometimes in depths of 1,950 fathoms. It is evident that, if large areas of the southern hemisphere were elevated into land, we should have phenomena to deal with not much unlike those of North America at present. Perhaps no discussion carries with it more of warning to geologists to exercise caution in framing theories than this of" the great ice age ; and if the collapse of extreme views on this subject shall have the effect of inducing geologists to keep within the limits of well-ascertained facts and sound induction, to adhere to the Lyellian doctrine of modern causes to ex- plain ancient phenomena, and to bear in mind that most great effects involve not one cause, but many co-operating causes, it may lead to consequences beneficial to science ; and so, emerg- ing from the cold shadows of the continental glacier, we may find ourselves in the sunshine of truth. REFERENCES : "Acadian Geology," ist ed., 1855; 4th ed., 1892. Ice- bergs of Belle-Isle, and Glaciers of Mont Blanc, Canadian Naturalist, 1865. "Notes on Pleistocene of Canada," Montreal, 1871. Papers at various dates in the Canadian Naturalist and Canadian Record oj Science. "The Ice Age in Canada," Montreal, 1893. Canadian Pleis- tocene, London Geological Magazine, March, 1883. Flora of the Pleistocene, Bulletin of Geological Society of America, vol. i., 1890, p. 311, Dawson and Penhallovv. CAUSES OF CLIMATAL CHANGE. DEDICATED TO DR. T. STERRY HUNT, F.R.S., WHOSE WORK IN THE CHEMICAL AND COSMICAL RELATIONS OF GEOLOGY IS BEYOND ALL PRAISE, AND IS DESTINED TO COMMAND IN THE FUTURE EVEN GREATER ACCEPTANCE THAN IN THE PAST. VARIOUS THEORIES AS TO CHANGES OF CLIMATE THE ASTRONOMICAL THEORY OF CROLL THE GEOGRAPHICAL THEORY OF LYELL OBJECTIONS OF A GEOLOGICAL CHARACTER TO THE FORMER TESTIMONY OF GEOLOGY AND PHYSICAL GEOGRAPHY IN FAVOUR OF THE LATTER CHAPTER XIV. CAUSES OF CLIMATAL CHANGE. THE subject of this chapter is one which has been in dis- pute ever since I began to read anything on geology, nearly sixty years ago. It ought to have been settled, but up to to-day one finds in geological works and papers especially those relating to the Glacial age the most divergent views ; and in the writings of men not geologists, it is not unusual to find exploded theories gravely stated as established facts of science. The subject is one which I cannot hope to make interesting, but if the reader will wade through a short chapter, he will be able to find some of the data on which statements on this subject in other papers of this series are based. Mr. Searles V. Wood, in an able summary of the possible causes of the succession of cold and warm climates in the northern hemisphere, enumerates no fewer than seven theories which have met with more or less acceptance, and he might have added an eighth. These are : (1) The gradual cooling of the earth from a condition of original incandescence. (2) Changes in the obliquity of the ecliptic. (3) Changes in the position of the earth's axis of rotation. (4) The effect of the precession of the equinoxes, along with changes of the eccentricity of the earth's orbit. (5) Variations in the amount of heat given off by the sun. (6) Differences in the temperature of portions of space passed through by the earth. 383 384 CAUSES OF CLIMATAL CHANGE (7) Differences in the distribution of land and water in con- nection with the flow of oceanic currents. (8) Variations in the properties of the atmosphere with reference to its capacity for allowing the radiation of heat. Something may be said in favour of all these alleged causes ; but as efficient in any important degree in producing the cold and warm climates of the Tertiary period, the greater number of them may be dismissed as incapable of effecting such results, or as altogether uncertain with reference to the fact of their own occurrence. (1) That the earth and the sun have diminished in heat during geological time seems probable ; but physical and geolo- gical facts alike render it certain that this influence could have produced no appreciable effect, even in the times of the earliest animals and plants, and certainly not in the case of Tertiary floras or faunas. (2) The obliquity of the ecliptic is not believed by astrono- mers to have changed to any great degree, and its effect would be merely a somewhat different distribution of heat in different periods of the year. (3) Independently of astronomical objections, there is good geological evidence that the poles of the earth must have been nearly in their present places from the dawn of life until now. From the Laurentian upward, those organic limestones which mark the areas where warm and shallow equatorial water was spreading over submerged continents, are so disposed as to prove the permanence of the poles. In like manner all the great foldings of the crust of the earth have followed lines which are parts of great circles tangent to the existing polar circles. So, also, from the Cambrian age the great drift of sediment from the north has followed the line of the existing Arctic currents from the north-east to the south-west, throwing itself, for example, along the line of the Appalachian uplifts in Eastern America, and against the ridge of the Cordilleras in the west. CAUSES OF CLIMATAL CHANGE 385 (4) The effects of change of eccentricity and precession have been so ably urged by Croll, and recently by Ball, and have so strongly influenced the minds of those who are not working geologists, that they deserve a more detailed notice. (5) The heat of the sun is known to be variable, and the eleven years' period of sun spots has recently attracted much attention as producing appreciable effects on the seasons. There may possibly be longer cycles of solar energy ; or the sun may be liable, like some variable stars, to paroxysms of in- creased energy. Such changes are possible, but we have no evidence of their occurrence, and they could not account for periods of refrigeration of limited duration like the Glacial age. (6) It has been supposed that the earth may have at dif- ferent times traversed more or less heated zones of space, giving alternations of warm and cold temperature. No such differences in space are, however, known, nor does there seem any good ground for imagining their existence. (7) The differences in the form and elevation of our conti- nents, and in the consequent distribution of surfaces of different absorbent and radiating power, and of the oceanic currents, are known causes of climatal change, and have been referred to in these papers as competent to account for many, at least, of the phenomena. (8) Reference has already been made, in connection with the distribution of plants, to the possibility that the primeval atmosphere was richer in carbon than that of more modern times, and that this might operate to produce diminution of radiation, and consequent uniformity of temperature ; but this cause could not have been efficient in the later geological periods. There may thus be said to remain two theories of those enumerated by Wood, to which more detailed consideration may be given, namely, numbers four and seven, which may be named s. E. 28 386 CAUSES OF CLIMATAL CHANGE respectively those of Croll and Lyell, or the astronomical and geographical theories. The late Mr. Croll has, in his valuable work " Climate and Time," and in various memoirs, brought forward an ingenious astronomical theory to account for changes of climate. This theory, as stated by himself, is that when the eccentricity of the earth's orbit is at a high value, and the northern winter solstice is in perihelion, agencies are brought into operation which make the south-east trade winds stronger than the north- east, and compel them to blow over upon the northern hemi- sphere as far as the Tropic of Cancer. The result is that all the great equatorial currents of the ocean are impelled into the northern hemisphere, which thus, in consequence of the im- mense accumulation of warm water, has its temperature raised, so that ice and snow must, tor a great extent, disappear from the Arctic regions. In the prevalence of the converse conditions the Arctic zone becomes clad in ice, and the southern has its temperature raised. At the same time, according to CrolPs calculations, the ac- cumulation of ice on either pole would tend, by shifting the earth's centre of gravity, to raise the level of the ocean and submerge the land on the colder hemisphere. Thus a sub- mergence of land would coincide with a cold condition, and emergence with increasing warmth. Facts already referred to, however, show that this has not always been the case, but that in many cases submergence was accompanied with the influx of warm equatorial waters and a raised temperature, this ap- parently depending on the question of local distribution of land and water ; and this, in its turn, being regulated not always by mere shifting of the centre of gravity, but by foldings occa- sioned by contraction, by equatorial subsidences resulting from the retardation of the earth's rotation, and by the excess of material abstracted by ice and frost from the Arctic regions, and drifted southward along the lines of arctic currents. This drift- CAUSES OF CLIMATAL CHANGE 387 ing must in all geological times have greatly exceeded, as it certainly does at present, the denudation caused by atmospheric action at the equator, and must have tended to increase the disposition to equatorial collapse occasioned by retardation of rotation. While such considerations as those above referred to tend to reduce the practical importance of Mr. Croli's theory, on the other hand they tend to remove one of the greatest objections against it namely, that founded on the necessity of supposing that glacial periods recur with astronomical regularity in geolo- gical time. They cannot do so if dependent on other causes inherent in the earth itself, and producing important move- ments of its crust. Sir Robert Ball has in a recent work very ingeniously im- proved this theory by showing that Croll was mistaken in assigning equal amounts of heat to the earth, as a whole, in the periods of greater and less eccentricity. This would tend to augment the effect of astronomical revolutions as causes of difference of temperature; but has no bearing on the more serious geological objections to the theory in question. . A fatal objection, however, to Croli's theory, the force of which has been greatly increased by recent discoveries, is that the astronomical causes which he adduces would place the close of the last Glacial period at least 80,000 years ago, where- as it is now certainly known from geological facts that the close of the last Glacial period cannot be older than about an eighth or a tenth of that time. This difficulty seems to have caused the greater number of geologists, specially acquainted with the later geological periods, to regard this theory as quite inapplic- able to the facts. 1 Croll, in "Climate and Time," and in a note read before the British Association in 1876, takes an opposite view ; but this is clearly contrary to the facts of sedimentation, which show a steady movement of debris toward the south and south-west. 388 CAUSES OF CL1MATAL CHANGE We are thus obliged to fall back upon the old Lyellian theory of geographical changes, \vith such modifications as recent dis- coveries have rendered necessary. Taking this as our guide, we reach at once the important conclusion that the movements and distribution of animals and plants, however dependent on climate, altitude and depth, have, when regarded in connection .with geological time, been primarily determined by those great movements of the crust of the earth which have established our islands, continents and ocean depths. These geographical changes have also in connection with animal and vegetable growth, deposition of sediments and volcanic ejections, fixed even the stations, soils and exposures of plants and animals. Thus, subject to those great astronomical laws which regulate the temperature of our planet as a whole, our attention may be restricted to the factors of physical geography itself. We must, however, carry with us the idea that though the great continents and the ocean depths may have been fixed through- out geological time, their relative elevations, and consequently their limits, have varied to a great extent, and are constantly changing. We must also remember that something more than mere cold is necessary to produce a glacial period. It has sometimes been assumed that the tendency of an exceptionally cold winter would necessarily be to accumulate so great a quantity of snow and ice, that these could not be removed in the short though warm summer, and so would go on accumulating from year to year. Actual experience and observation do not confirm this supposition. In those parts of North America which have a long and severe winter, the amount of snow deposited is not in proportion to the lowness of the temperature, but, on the con- trary, the greatest precipitation of snow takes place near the southern margin of a cold area, and the snow disappears with great rapidity when the spring warmth sets in. Nor is there, as has been imagined, any tendency to the production of fogs and CAUSES OP^ CLIMATAL CHANGE 389 mists which have been invoked as agencies to shield the snow from the sun. In North America the melting snow is ordinarily carried off as liquid water, or as invisible vapour, and the sky is usually clear when the snow is melting in spring. It is only when warm and moist winds are exceptionally thrown upon the snow-covered land that clouds are produced ; and when this is the case, the warm rain that ensues promotes the melting of the snow. Thus there is no possibility of continued accumulations of snow on the lower parts of our continents, under any imagin- able conditions of climate. It is only on elevated lands in high latitudes and near the ocean, like Greenland and the Antarctic continent, that such permanent snow-clad conditions can occur, except on mountain tops. Wallace and Wceickoff 1 very pro- perly maintain, in connection with these facts, that permanent ice and snow cannot under any ordinary circumstances exist in low lands, and that high land and great precipitation are neces- sary conditions of glaciers. The former, however, attaches rather too much importance to snow and ice as cooling agents ; for though it is true that they absorb a large amount of heat in passing from the solid to the liquid state, yet the quantity of snow or ice to be melted in spring is so small in comparison with the vast and continuous pouring of solar heat on the sur- face, that a very short time suffices for the liquefaction of a deep covering of snow. The testimony of Siberian travellers proves this, and the same fact is a matter of ordinary observation in North America. Setting aside, then, these assumptions, which proceed from incorrect or insufficient information, we may now refer to a con- sideration of the utmost importance, and which Mr. Croll him- self, though he adduces it only in aid of the astronomical theory of glacial periods, has treated in so masterly a manner, as 1 Von Wceickoff has very strongly put these principles in a Review of Croll's recent book, "Climate and Cosmology"; American Journal of Science, March, 1886. 390 CAUSES OF CLIMATAL CHANGE really to give it the first place as an efficient cause. This is the varying distribution of ocean currents, in connection with the differences in the elevation and distribution of land. The great equatorial current, produced by the action of the solar heat on the atmosphere and the water, along with the earth's rotation, is thrown, by opposing continental shores, northward into the Atlantic and Pacific in the Gulf Stream and Japan current, giving us a hot-water apparatus which effectually raises the tem- perature of the whole northern hemisphere, and especially of the western sides of the continents. Mr. Croll imagined that .if his astronomical causes could, to ever so small an extent, in- tensify the action of these currents, or their determination to the north, we should have a period of warmth, while a similar advantage given to the southern hemisphere would produce a glacial age in the north. But this requires us to assume what ought to be proved ; namely, that the position of aphelion, and the increase or decrease of eccentricity, would actually so swing the equatorial current to the north or south. It further requires us to assume and this is the most important defect of the theory that no change occurs in the distribution of land and water ; because any important change of this kind might obviously exert a dominant influence on the currents. Let us take two examples in illustration of this. At the present time the warm water thrown into the North Atlantic, co-operating with the prevalent westerly winds, not only increases the temperature of its whole waters, but gives an exceptionally mild climate to western Europe. Still the counter- vailing influence of the Arctic currents and the Greenland ice, is sufficient to permit numerous icebergs to remain unmelted on the coast of Labrador and Newfoundland throughout the sum- mer. Some of the bergs which creep down to the mouth of the Strait of Belle-Isle, in the latitude of the south of England, actually remain unmelted till the snows of a succeeding winter fall upon them. Now let us suppose that a subsidence of land CAUSES OF CLIMATAL CHANGE 39 1 in tropical America were to allow the equatorial current to pass through into the Pacific. The effect would at once be to re- duce the temperature of Norway and Britain to that of Green- land and Labrador at present, while the latter countries would themselves become colder. The northern ice, drifting down into the Atlantic, would not, as now, be melted rapidly by the warm water which it meets in the Gulf Stream. Much larger quantities of it would remain undissolved in summer, and thus an accumulation of permanent ice would take place, along the American coast at first, but probably at length even on the European side. This would still further chill the atmosphere, glaciers would be established on all the mountains of temperate Europe and America, the summer would be kept cold by melting ice and snow, and at length all eastern America and Europe might become uninhabitable, except by Arctic animals and plants, as far south as perhaps 40 of north latitude. This would be simply a return of the glacial age. I have assumed only one geographical change ; but other and more complex changes of subsidence and elevation might take place, with effects on climate still more decisive. 1 We may suppose an opposite case. The high plateau of Greenland might subside, or be reduced in height, and the opening of Baffin's Bay might be closed. At the same time the interior plain of America might be depressed, so that, as we know to have been the case in the Cretaceous period, the warm waters of the Mexican gulf might circulate as far north as the basins of the present great American lakes. In these cir- cumstances there would be an immense diminution of the sources of floating ice, and a correspondingly vast increase in the surface of warm water. The effects would be to enable a 1 According to Bonney, the west coast of Wales is about 12 above the average for its latitude, and if reduced to 12 below the average, its moun- tains would have large glaciers. So near is England even now to a glacial age. 392 CAUSES OF CLIMATAL CHANGE temperate flora to subsist in Greenland, and to bring all the present temperate regions of Europe and America into a con- dition of subtropical verdure. It is only necessary to add that we actually know that changes not dissimilar from those above sketched have really occurred in comparatively recent geological times, to enable us to perceive that we can dispense with all other causes of change of climate, though admitting that some of them may have occu- pied a secondary place. This will give us, in dealing with the distribution of life, the great advantage of not being tied up to definite astronomical cycles of glaciation, which do not well agree with the geological facts, and of correlating elevation and subsidence of the land with changes of climate affecting living beings. It will, however, be necessary, as Wallace well insists, that we shall hold to a certain fixity of the continents in their position, notwithstanding the submergences and emergences which they have experienced. Sir Charles Lyell, more than forty years ago, published in his " Principles of Geology ' : two imaginary maps, which illustrate the extreme effects of various distribution of land and water. In one, all the continental masses are grouped around the equator. In the other they are all placed around the poles, leaving an open equatorial ocean. In the one case the whole of the land and its inhabitants would enjoy a perpetual summer, and scarcely any ice could exist in the sea. In the other, the whole of the land would be subjected to an Arctic climate, and it would give off immense quantities of ice to cool the ocean. Sir Charles remarks on the present apparently capricious distri- bution of land and water, the greater part being in the northern hemisphere, and, in this, placed in a .very unequal manner. But Lyell did not suppose that any such distribution as that represented in his maps had actually occurred, though this supposition has been sometimes attributed to him. He merely put what he regarded as an extreme case to illustrate what CAUSES OF CLIMATAL CHANGE 393 might occur under conditions less exaggerated. Sir Charles, like all other thoughtful geologists, was well aware of the gen- eral fixity of the areas of the continents, though with great modifications in the matter of submergences and of land con- ditions. The union, indeed, of these two great principles of fixity and diversity of the continents lies at the foundation of theoretical geology. We can now more precisely indicate this than was possible when Lyell produced his "Principles," and can reproduce the conditions of our continents in even the more ancient periods of their history. An example of this may be given from the American continent, which is more simple in its arrangements than the double continent of Eurasia. Take, for instance, the early Devonian or Erian period, in which the magnificent flora of that age, the earliest certainly known to us, made its appear- ance. Imagine the whole interior plain of North America submerged, so that the continent is reduced to two strips on the east and west, connected by a belt of Laurentian land on the north. In the great mediterranean sea thus produced, the tepid water of the equatorial current was circulated, and it swarmed with corals, of which we know no less than 150 species, and with other forms of life appropriate to warm seas. On the islands and coasts of this sea was introduced the Erian flora, appearing first in the north, and with that vitality and colonizing power of which, as Hooker has well shown, the Scandinavian flora is the best modern type, spreading itself to the south. A very similar distribution of land and water in the Cretaceous age gave a warm and equable climate in those portions of North America not submerged, and coincided with the appearance of the multitude of broad-leaved trees of modern types which ap- peared in the middle Cretaceous, and prepared the way for the mammalian life of the Eocene. We have in America ancient periods of cold as well as of warmth. I have elsewhere referred to the boulder conglomer- 394 CAUSES OF CLIMATAL CHANGE ates of the Huronian, of the early Lower Silurian, and of the Millstone grit period of the Carboniferous ; but I have not ven- tured to affirm that either of these periods was comparable in its cold with the later glacial age, still less with that imaginary age of continental glaciation, assumed by the more extreme theorists. We know that these ancient conglomerates were produced by floating ice, and this at periods when in areas not very remote, temperate floras and faunas could flourish. The glacial periods of our old continent occurred in times when the surface of the submerged land was opened up to the northern currents drifting over it mud and sand and stones, and render- ing nugatory, in so far, at least, as the bottom of the sea was concerned, the effects of the superficial warm streams. Some of these beds are also peculiar to the eastern margin of the continent, and indicate ice drift along the Atlantic coast much as at present, while conditions of greater warmth existed in the interior. Even in the more recent glacial age, while the moun- tains were covered with snow, and the low lands submerged under a sea laden with ice, there were interior tracts in some- what high latitudes of America in which hardy forest trees and herbaceous plants flourished abundantly, and these were by no means exceptional "interglacial" periods. Thus we can prove that from the remote Huronian period to the Tertiary, the American land occupied the same position as at present, and that its changes were merely changes of relative level, as com- pared with the sea ; but which so influenced the ocean currents as to cause great vicissitudes of climate. Uniformitarian geologists have recently been taunted with a willingness to assume great and frequent elevations and sub- mergences of continents, as if this were contrary to their principle. But rational uniformitarianism allows us to use any cause of whose operation in the past there is good geological evidence, and Lyell himself was perfectly aware of this. While no geologists can fail to appreciate the evidence of CAUSES OF CLIMATAL CHANGE 395 the power of geographical change in affecting climatal change, and the fact that such change has occurred at various geo- logical periods, there are some, and especially those who take extreme views as to the latest period of cold climate, who doubt its sufficiency to account for all the phenomena ob- served. It is instructive, however, to notice that some of the ablest of these, in default of other probable causes, are driven to fall back either on agencies of a wholly improbable character, or to give up the problem as insoluble. Two recent examples of this deserve citation. The late Dr. Newmayr, of Vienna, a veteran physical geo- grapher, in an able discussion of the climates of past ages, one of his last scientific papers, has fallen back on the hypo- thesis of a change in the position of the poles. 1 His failure to account for ancient climates by other causes evidently, however, depends on an inadequate conception of the effects of geographical changes, along with serious misconceptions as to the distribution of plants and the characters of vege- tation at different periods. These points we shall have to discuss in subsequent pages. In an address before the American Association, in 1886, Dr. Chamberlain, one of the ablest American authorities on the Glacial period, makes the following remarks as to the causes of the Pleistocene cold : "If we turn to the broader speculations respecting the origin of the Glacial epoch, we find our wealth little increased. We have on hand practically the same old stock of hypotheses, all badly damaged by the deluge of recent facts. The earlier theory of northern elevation has been rendered practically valueless; and the various astronomical hypotheses seem to be the worse for the increased knowledge of the distribution of the ancient ice sheet. Even the ingenious theory of Croll 1 Society for Dissemination of Natural Science. Vienna, January, 1889. 396 CAUSES OF CL1MATAL CHANGE becomes increasingly unsatisfactory as the phenomena are developed into fuller appreciation. The more we consider the asymmetry of the ice distribution in latitude and longitude, and its disparity in elevation, the more difficult it becomes to explain the phenomena upon any astronomical basis. If we were at liberty to disregard the considerations forced upon us by physicists and astronomers, and permit ourselves simply to follow freely the apparent leadings of the phenomena, it appears at this hour as though we should be led upon an old and forbidden trail, the hypothesis of a wandering pole. It is admitted that there is a vera causa in elevations and de- pressions of the earth's crust, but it is held inadequate. It is admitted that the apparent changes of latitude shown by the determinations of European and American observatories are remarkable, but their trustworthiness is challenged. Were there no barriers against free hypotheses in this direction, glacial phenomena could apparently find adequate explanation ; but debarred as we doubtless should consider ourselves to be at present from this resource, our hypotheses remain inharmonious with the facts, and the riddle remains unsolved." It should be observed here that the unsolved " riddle " is that of a continental ice sheet. This, as we have already seen, is probably insoluble in any way, but fortunately needs no solution, being merely imaginary. If we adopt a moderate view as to the actual conditions of the Pleistocene, the geo- graphical theory will be found quite sufficient to account for the facts. Let it be observed here also, in connection with the above thoughtful and frank avowal of one of the ablest of American glacialists, that the geographical theory provides for that " asymmetry " or irregular distribution of glacial deposits to which he refers ; since, at every stage of continental elevation and depression, there must have been local changes of cir- cumstances; and the same inequality of temperature in identical CAUSES OF CLIMATAL CHANGE 397 latitudes which we observe at present must have existed, prob- ably in a greater degree, in the Glacial age. The sufficiency of the Lyellian theory to account for the facts, in so far as plants are concerned, may, indeed, be inferred from the course of the isothermal lines at present. The south end of Greenland is on the latitude of Christiania, in Norway, on the one hand, and of Fort Liard, in the Peace River region, on the other ; and while Greenland is clad in ice and snow, wheat and other grains, and the ordinary trees of temperate climates, grow at the latter places. It is evident, therefore, that only exceptionally unfavourable circumstances prevent the Greenland area from still possessing a temperate flora, and these unfavourable circumstances possibly tell even on the localities with which we have compared it. Further, the mouth of the McKenzie River is in the same latitude with Disco, near which are some of the most celebrated localities of fossil Cretaceous and Tertiary plants. Yet the mouth of the McKenzie River enjoys a much more favourable climate, and has a much more abundant flora than Disco. If North Greenland were submerged, and low land reaching to the south terminated at Disco, and if from any cause either the cold currents of Baffin's 'Bay were arrested, or additional warm water thrown into the North Atlantic by the Gulf Stream, there is nothing to prevent a mean temperature of 45 Fahrenheit from prevailing at Disco ; and the estimate ordinarily formed of the requirements of its extinct floras is 50, which is probably above, rather than below, the actual temperature required. We thus know that the present distribution of land and water greatly influences climate, more especially by affecting that of the ocean currents and of the winds, and by the different action of land as compared with water in the recep- tion and radiation of heat. The present distribution of land gives a large predominance to the Arctic and sub-Arctic regions, 398 CAUSES OF CLIMATAL CHANGE as compared with the equatorial and with the Antarctic ; and we might readily imagine other distributions that would give very different results. But this is not an imaginary case, for we can to some extent restore, on geological grounds, the ancient geography of large regions, and can show that it has been very different from that prevailing at present. We know also that, while the forms and positions of the great continents have been fixed from a very early date, they have experienced many great submergences and re-elevations, and that these have occurred in somewhat regular sequence, as evidenced by the cyclical alternations of organic limestones and earthy sediments in the successive great geological periods, each of which, as may be seen in any geological text book, presents a dip of the continental plateaus, with subsequent elevation, as if the land was subject to a series of regular pulsations. 1 Finally, the Lyellian theory tends to abate the tendency to imagine portentous and impossible climatal changes; and it inclines geologists to give more attention to the connection of palaso-geography with changes in the life history of the earth. REFERENCES: "Acadian Geology," ist ed., 1855 ; 4th ed., 1892. Ice- bergs of Belle-Isle, and Glaciers of Mont Blanc, Canadian Naturalist, 1865. "Notes on Pleistocene of Canada," Montreal, 1871. Papers at various dates in the Canadian Naturalist and Canadian Record of Science. "The Ice Age in Canada," Montreal, 1892. Canadian Pleistocene, London Geological Magazine, March, 1883. Flora of the Pleistocene, Dawson and Penhallow. Bulletin of Geological Society of America, vol. i., 1890, p. 311. 1 See "Acadian Geology "Introduction to the Carboniferous System. THE DISTRIBUTION OF ANIMALS AND PLANTS AS RELATED TO GEOGRAPHICAL AND GEOLOGICAL CHANGES. DEDICATED TO THE MEMORY OF MY LATE FRIEND, MR. GWYN JEFFRIES, WHO SO ABLY INVESTIGATED THE DISTRIBUTION OF OCEANIC MOLLUSKA, MORE ESPECIALLY IN THE NORTH ATLANTIC. CHANGES OF CLIMATE AND OF LAND AND WATER WITH REFERENCE TO DISTRIBUTION OF LIFE REGIONS OF THE CONTINENTS INSULAR FAUNAS AND FLORAS THEIR HISTORY APPLICATIONS TO GEOLOGY AND TO MAN GEOLOGICAL TIME THEORIES OF INTRODUCTION AND MIGRATION S. E. VERTEBRATA PALEOZOIC MESOZOIC KAINOZOIC MODERN INVERTEBRATA. PALEOZOIC MESOZOIC KAINOZOIC MODERN DISTRIBUTION OF ANIMALS IN TIME. (p. 420.) Vertebrata. i, Ganoid Fishes; 2, Teliort Fishes; 3, Batrachians; 4, Reptiles ; 5, Birds ; 6, Mammals. Invertebrata. I , Trilobites, etc. ; 2, Worms ; 3, Bivalve and Univalve Shellfishes ; 4, Nautiloid Shellfishes ; 5, Cuttlefishes. It will be noticed that Nos. 2 and 5 in the first table, and 3 and 5 in the second, follow a different order of curve from the others, indicating their exceptional culmination in modern times. CHAPTER XV. THE DISTRIBUTION OF ANIMALS AND PLANTS AS RELATED TO GEOGRAPHICAL AND GEOLOGICAL CHANGES. A^L are now agreed that to explain the extraordinary and often apparently anomalous distribution of animals and plants over the surface of the earth, and the occurrence of like forms in very distant localities, and even on islands separated by vast stretches of ocean from one another and from the continents, we must invoke the aid of geology. We must have reference to those changes of climate and of eleva- tion which have occurred in the more recent periods of the earth's history, and must carry with us the idea, at first not apparently very reasonable, that living beings have existed much longer than many of the lands which they inhabit, or at least than the present state of those lands in reference to isolation or continental connection. To what extent we may further require to call in the aid of varietal or specific modification to explain the facts, may be more doubtful ; and I think we shall find that a larger acquaintance with geological truths would enable us to dispense with the aid of hypotheses of evolution, at least in so far as the local establishment of new generic and specific types is concerned. One of the most remarkable and startling results of geo- logical investigation, and one which must be accepted as an established fact, independently of all theoretical explanations, is that the earth has experienced enormous revolutions of 4O2 THE DISTRIBUTION OF ANIMALS AND PLANTS climate within comparatively late periods, and since the date of the introduction of many existing species of animals and plants. To this great truth, in some of its bearings, I have endeavoured to direct attention in the previous articles. In the present case it will be necessary to consider these vicis- situdes in their more general aspects, and with some reference to their effects on the distribution of living beings. The modern or human period of geology, that in which man and his contemporaries are certainly known to have inhabited the earth, was immediately preceded by an age of climatal refrigeration known as the Glacial or Ice age. This was further characterized not only by a prevalence of cold, unexampled so far as known either before or since, but by immense changes of the relative levels of sea and land, amounting, in some cases, at least, to several thousands of feet. The occurrence of these changes is clearly proved by the undoubted traces of the action of ice, whether land fee or floating ice, on all parts of our continents, half way to the equator, and by the occurrence of sea terraces and modern marine shells at high levels on mountains and table-lands. Perhaps we scarcely realize as we should the stupendous character of the changes involved in the driftage of heavy ice over our continents as far south as the latitude of 40, in the deposit of boulders on hills several thousands of feet in height, and in the occurrence of shells of species still living in the sea, in beds raised to more than twelve hundred feet above its present level. Yet such changes must have occurred in the latest geological period immediately preceding that in which we live. Proceeding farther back in geological time, we find the still more extraordinary fact that in the middle and earlier Tertiary the northern hemisphere enjoyed a climate so much more mild than that which now prevails, that plants at present confined to temperate latitudes could flourish in THE DISTRIBUTION OF ANIMALS AND PLANTS 403 Greenland and Spitzbergen. 1 The age in which we live is thus one of mediocrity, attaining neither to the Arctic rigour of the later Pleistocene, nor to the universal mildness of the preceding Miocene. The causes of these changes of climate we have discussed elsewhere. It remains for us now to consider the actual condition of our present continents, and the bearing of past conditions on the distribution of their living inhabitants. In speaking of continents and islands, it may be as well to remark at the outset that all the land existing, or which probably has at any time existed, consists of islands great or small. It is all surrounded by the ocean. Two of the greater masses of land are, however, sufficiently extensive to be regarded as continents, and from their very extent and consequent permanence may be considered as the more special homes of the living beings of the land. Two other portions of land, Australia and the Antarctic polar continent, may be regarded either as smaller continents or large islands, but partake of insular rather than continental characters in their animals and plants. All the other portions of land are pro- perly islands; but while these islands, and more especially those in mid-ocean, cannot be regarded as the original homes of many forms of life, we shall find that they have a special interest as the shelters and refuges of numerous very ancient and now decaying species. The two great continents of America and Eurasia have been the most permanent portions of the land throughout geological time, some parts of them having always been above water, probably from the Laurentian age downward, though at various times they have been reduced to little more than groups of islands. On them, and more especially in their more northern 1 As I have elsewhere shown, a warm climate in an Arctic region seems to have afforded the necessary conditions for the great colonizing floras of all geological periods. 404 THE DISTRIBUTION OF ANIMALS AND PLANTS parts, in which the long continuance of daylight in summer seems in warm periods to have been peculiarly favourable to the introduction of new vegetable and animal forms, and to the giving to them that vigour necessary for active colonization, have originated the greater number of the inhabitants of the land. Regarded as portions of the earth's crust, the continents are areas in which the lateral thrust, caused by the secular con traction of the interior of the earth and unequal settlement of the crust, has ridged up and folded the rocks, producing mountain chains. This process began in the earliest geological periods, and has been repeated at long intervals, the original lines of folding guiding those formed in each new thrust pro- ceeding from the broad oceanic areas. Along the ridges thus produced, and in the narrower spaces between them, the greater part of the sediment carried by water was laid down, thus producing plateaus in connection with the mountain- chains, while the weight of new sediments and the removal of matter from other areas by denudation, have been constantly producing local depression and elevation. The tendency of the ocean to be thrown toward the poles by the retardation of the earth's rotation, alternating with great collapses of the crust at the equator proceeding from the same cause, along with the secular cooling, have produced alternate submer- gence and emergence of these plateaus. This has been further complicated by the constant tendency of the Arctic and Antarctic currents, aided by ice, to drift solid materials, set free by the vast denuding action of frost, from the polar to the temperate regions, and by the further tendency of animal life to heap up calcareous accumulations under the warm waters of the tropical regions. All these changes, as already stated, have conspired to modify the directions of the great oceanic cur- rents, and to produce vicissitudes of climate under which animals and plants have been subjected in geological time to THE DISTRIBUTION OF ANIMALS AND PLANTS 405 those migrations, extinctions, and renovations of which their fossil remains and present distribution afford evidence. Still, it is true that throughout the whole of these great mutations, since the beginning of geological history, there seems never to have been any time when the ocean so regained its dominion as to produce a total extinction of land life ; still less was there any time when the necessary conditions of all the various forms of marine life failed to be found ; nor was there any climatal change so extreme as to banish any of the leading forms of life from the earth. To geologists it is not necessary to say that the conclusions sketched above are those that have been reached as the results of long and laborious investigation, and which have been illustrated and established by Lyell, Dana, Wallace, 1 and many other writers. 2 Let us now place beside them some facts as to the present distribution of life, and of the agencies which influence it. Just as political geography sometimes presents boundaries not in accordance with the physical structure of countries, so the distribution of animals and plants shows many peculiar and unexpected features. Hence naturalists have divided the continents into what Sclater has called zoological regions, which are, so to speak, the great empires of animal life, divisible often by less prominent boundaries into provinces. In vege- table life similar boundaries may be drawn, more or less coin- cident with the zoological divisions. Zoologically, North America and Greenland may be regarded as one great region, the Nearctic, or new Arctic, the prefix not indicating that the animals are newer than those of the old world, which is by no means the case. South America constitutes another region 1 Wallace, " Geographical Distribution of Animals" and "Island Life." Second edition. 2 The writer has endeavoured to popularize these great results of geology in his work, the "Story of the Earth." Ninth Edition. London, 1887. They are often overlooked by specialists, and by compilers of geological manuals. 406 THE DISTRIBUTION OF ANIMALS AND PLANTS the Neotropical. If now we turn to the greater Eurasian con- tinent, with its two prolongations to the south in Africa and Australia, we shall find the whole northern portion, from the Atlantic to the Pacific, constituting one vast region of animal life, the Palearctic, which also includes Iceland and a strip across North Africa. Africa itself, with Madagascar, whose allegiance is, however, only partial, constitutes the Ethiopian region. India, Burmah, the south of China, and certain Asiatic islands form the Oriental region. Australia, New Guinea, and the Polynesian islands constitute the Australian region. All of these regions may in a geological point 01 view be considered as portions of old and permanent contin- ental masses, which, though with movements of elevation and depression, have continued to exist for vast periods. Some of them, however, seem to have enjoyed greater immunity from causes of change than others, and present, accordingly, animals and plants having, geologically speaking, an antique aspect in comparison. In this sense the Australian province may be re- garded as the oldest of all in the facies of its animal forms, since creatures exist there of genera and families which have very long ago become extinct everywhere else. Next in age to this should rank the Neotropical or South American region, which, like Australia, presents many low and archaic forms of animal life. The Ethiopian region stands next to it in this, the Oriental and Nearctic next, and last and most modern in its aspect is the great Palearctic region, to which man himself be- longs, and the animals and plants of which vindicate their claims to youth by that aggressive and colonizing character already referred to, and which has enabled them to spread themselves widely over the other regions, even independently of the in- fluence of man. On the other hand, the animals and plants of the Australian aud South American regions show no such colonizing tendency, and can scarcely maintain themselves against those of other regions when introduced among them. THE DISTRIBUTION OF ANIMALS AND PLANTS 407 Thus we have at once in these continental regions a great and suggestive example of the connection of geographical and geo- logical distribution, the details of which are of the deepest in- terest, and have not yet been fully worked out. One great principle is, however, sufficiently established ; namely, that the northern regions have been the birthplace of new forms of land life, whence they have extended themselves to the south, while the comparative isolation and equable climate of the South American and Australian regions have enabled them to shelter and retain the old moribund tribes. Those smaller portions of land separated from the con- tinental masses, the islands properly so called, present, as might be expected, many peculiar features. Wallace divides them into two classes, though he admits that these pass into each other. Continental islands are those in the vicinity ot continents. They consist of ancient as well as modern rock formations, and contain animals which indicate a former continental connection. Some of these are separated from the nearest mainland only by shallow seas or straits, and may be assumed to have become islands only in recent geological times. Others are divided from the nearest continent by very deep water, so that they have probably been longer severed from the mainland. These contain more peculiar assemblages of animals and plants than the islands of the former class. Oceanic islands are more remote from the continents. They consist mostly of rocks belonging to the modern geological periods, and contain no animals of those classes which can migrate only by land. Such islands may be assumed never to have been connected with any continent. The study of the indigenous population of these various classes of islands affords many curious and interesting results, which Wallace has collected with vast industry and care, and which, on the whole, he explains in a judicious manner and in accordance with the facts of geology. When, however, he maintains that 408 THE DISTRIBUTION OF ANIMALS AND PLANTS evolution of the Darwinian type is " the key to distribution," he departs widely from any basis of scientific fact. This be- comes apparent when we consider the following results, which appear everywhere in the discussion of the various insular faunas and floras : (i) None of these islands, however remote, can be affirmed to have been peopled by the spontaneous evolution of the higher animals or plants from lower forms. Their population is in every case not autochthonous, but de- rived. (2) Even in those which are most distant from the continents, and may be supposed to have been colonized in very ancient times, there is no evidence of any very important modification of their inhabitants. (3) While the facts point to the origin of most forms of terrestrial life in the Palearctic and Nearctic regions, they afford no information as to the manner or cause of their origination. In short, so far is evo- lution from being a key to distribution, that the whole question would become much more simple if this element were omitted altogether. A few examples may be useful to illustrate this, as well as the actual explanation of the phenomena afforded by legitimate science. The Azores are situated in a warm temperate latitude about 900 miles west of Portugal, and separated from it by a sea 2,500 fathoms in depth. The islands themselves are al- most wholly volcanic, and the oldest rocks known in them are of late Miocene age. There is no'probability that these islands have ever been connected with Europe or Africa, nor is there at present any certainty that they have been joined to one another, or have formed part of any larger insular tract. In these islands there is only one indigenous mammal, a bat, which is identical with a European species, and no doubt reached the islands by flight. There is no indigenous reptile, amphibian, or fresh-water fish. Of birds there are, exclusive of waterfowl, which may be regarded as visitors, twenty-two land birds ; but of these, four are regarded as merely accidental THE DISTRIBUTION OF ANIMALS AND PLANTS 409 stragglers, so that only eighteen are permanent residents. Of these birds fifteen are common European or African species, which must have flown to the islands, or have been drifted thither in storms. Of the remaining three, two are found also in Madeira and the Canaries, and therefore may reasonably be supposed to have been derived from Africa. One only is regarded as peculiar to the Azores, and this is a bullfinch, so nearly related to the European bullfinch that it may be regarded as merely a local variety. Wallace accounts for these facts by supposing that the Azores were depopulated by the cold of the Glacial age, and that all these birds have arrived since that time. There is, however, little probability in such a supposi- tion. He further supposes that fresh supplies of stray birds from the mainland, arriving from time to time, have kept up the identity of the species. Instead of evolution assisting him, lie has thus somewhat to strain the facts to agree with that hypothesis. Similar explanations are given for the still more remarkable fact that the land plants of the Azores are almost wholly identical with European and African forms. The in- sects and the land snails are, however, held to indicate the evolution of a certain number of new specific forms on the islands. The beetles number no less than 212 species, though nearly half of them are supposed to have been introduced by man. Of the whole number 175 are European, 19 are found in Madeira and the Canaries, 3 are American. Fourteen remain to be accounted for, though most of these are closely allied to European and other species ; but a few are quite dis- tinct from any elsewhere known. Wallace, however, very truly remarks that our knowledge of the continental beetles is not complete ; that the species in question are small and obscure ; that they may be survivors of the Glacial period, and may thus represent species now extinct on the mainland ; and that for these reasons it may not be irrational to suppose that these peculiar insects either still inhabit, or did once inhabit, some 4IO THE DISTRIBUTION OF ANIMALS AND PLANTS part of the continents, and may be portions of " ancient and widespread groups," once widely diffused, but now restricted to a few insular spots. Among the land snails, if anywhere, we should find evidence either of autochthonous evolution or of specific change. These animals have existed on the earth since the Carboniferous period, and, notwithstanding their proverbial slowness and sedentary habits, they have contrived to colonize every habitable spot of land on the globe that is, unless in some of these places they have originated de novo. In the Azores there are sixty-nine species of land snails, of which no less than thirty-two, or nearly one-half, are peculiar, though nearly all are closely allied to European types. What, then, is the origin of these thirty-two species, admitting for the sake of argument that they are really distinct, and not merely varietal forms, though it is well known that in this group species are often unduly multiplied. Three suppositions are possible, (i) These snails may have originated in the islands themselves, either by creation or evolution from lower forms ; say, from sea snails. (2) They may have been modified from modern con- tinental species. (3) They may be unmodified descendants of species of Miocene or Pliocene age now existing on the continents only as fossils. As the islands appear to have ex- isted since Miocene times, it is no more improbable that species of that or the Pliocene age should have found their way to them than that modern species should ; and as we know only a fraction of the Tertiary species of Europe or Africa, it is not likely that we shall be able to identify all of these early visitors. Unfortunately no Miocene or Pliocene deposits holding remains of land snails are known in the Azores themselves, so that this kind of evidence fails us. In Madeira and Porto Santo, however, where there are numerous modern snails, there are Pliocene beds holding remains of these animals. In Madeira there are, according to Lyell, 36 Plio- cene species, and in Porto Santo 35, and of these only eight THE DISTRIBUTION OF ANIMALS AND PLANTS 411 are extinct. Thus we can prove that many of the peculiar species of these islands have remained unchanged since Plio- cene times. While differing from modern European shells, several of these species are very near to European Miocene species. Thus we seem to have evidence in the Madeira group, not of modification, but of unchanged survival of Ter- tiary species long since extinct in Europe. May we not infer that the same was the case in the Azores ? These results are certainly very striking when we consider how long the Azores must have existed as islands, how very rarely animals, and es- pecially pairs of animals, must have reached them, and how- complete has been the isolation of these animals, and how peculiar the conditions to which they have been subjected in their island retreat. Other oceanic islands present great varieties of conditions, but leading to similar conclusions. Some, as the Bermudas, seem to have been settled in very modern times with animals and plants nearly all identical with those of neighbouring coun- tries, though even here it would appear that there are some indigenous species which would indicate a greater age or more extended lands, now submerged. 1 Others, like St. Helena, are occupied apparently with old settlers, which may have come to them in early Tertiary, or even in Secondary periods, which have long since become extinct on the continents, and whose nearest analogues are now widely scattered over the world. Islands are therefore places of survival of old species special preserves for forms of life lost to the continents. One of the most curious of these is Celebes, which seems to be a surviving fragment of Miocene Asia, which, though so near to that con- tinent, has been sufficiently isolated to preserve its old popula- 1 Heilprin mentions eleven marine mollusks supposed to be peculiar to the islands, and eight species of land shells, as well as a few Crustaceans hither- to found only in the Pacific. The comparisons are, however, admitted to be incomplete. 412 THE DISTRIBUTION OF ANIMALS AND PLANTS tion during all the vast lapse of time between the middle Tertiary and the present period. This is a fact which gives to the oceanic islands the greatest geological interest, and induces us to look into their actual fauna and flora for the representatives of species known on the mainland only as fossils. It is thus that we look to the marsupials of Australia as the nearest analogues of those of the Jurassic of Europe, and that we find in the strange Barramunda (ceratodus) of its rivers the only survivor of a group of fishes once widely distri- buted, but which has long since perished elsewhere. Perhaps one of the most interesting examples of this is furnished by the Galapagos Islands, an example the more re- markable that no one who has read in Darwin's fascinating " Journal " the description of these islands, can have failed to perceive that the peculiarities of this strange Archipelago must have been prominent among the facts which first planted in his mind the germ of that theory of the origin of species which has since grown to such gigantic dimensions. It is curious also to reflect that had the bearing of geological history on the facts of distribution been as well known forty years ago as it is now, the reasoning of the great naturalist on this and similar cases might have taken an entirely different direction. The Galapagos are placed exactly on the equator, and there- fore out of reach of even the suspicion of having been visited by the glacial cold, though from their isolation in the ocean, and the effects of the currents flowing along the American coast, their climate is not extremely hot. They are 600 miles west of South America, and the separating ocean is in some parts 3,000 fathoms deep. The largest of the islands is 75 miles in length, and some of the hills attain an elevation of about 4,000 feet, so that there are considerable varieties of station and climate. So far as is known they are wholly vol- canic, and they may be regarded as the summits of submerged mountains not unlike in structure to the Andes of the main- THE DISTRIBUTION OF ANIMALS AND PLANTS 413 land. Their exact geological age is unknown, but there is no improbability in supposing that they may have existed with more or less of extension since the Secondary or Mesozoic period. In any case their fauna is in some respects a survival of that age. Lyell has truly remarked, " In the fauna of the Galapagos Islands we have a state of things very analogous to that of the Secondary period." Like other oceanic islands, the Galapagos have no indigenous mammals, with the doubtful exception of a South American mouse ; but, unlike most others, they are rich in reptiles. At the head of these stand several species of gigantic tortoises. This group of animals, so far as known, commenced its exist- ence in the Eocene Tertiary ; and in this and the Miocene period still more gigantic species existed on the continents. It has been supposed that at some such early date they reached the Galapagos from South America. Another group of Gala- pagan reptiles, perhaps still more remarkable, is that of iguana- like lizards of the genus Amblyrhyncus, which are vegetable feeders, one of them browsing on marine weeds. They recall the great iguana-like reptiles of the European VVealden, and stand remote from all modern types. There are also snakes of two species, but these are South American forms, and may have drifted to the islands in comparatively recent times on floating trees. The birds are a curious assemblage. A few are common American species, like the rice bird. Others are quaint and peculiar creatures, allied to South American birds, but probably representing forms long since extinct on the continent. The bird fauna, as Wallace remarks, indicates that some of these animals are old residents, others more recent arrivals ; and it is probable that they have arrived at various times since the early Tertiary. He assumes that the earlier arrivals have been modified in the islands " into a variety of distinct types "; but the only evidence of this is that some of the species are closely related to each other. It is more likely 414 THE DISTRIBUTION OF ANIMALS AND PLANTS that they represent to our modern eyes the unmodified descend- ants of continental birds of the early Tertiary. Darwin re- marks that they are remarkably sombre in colouring for equa- torial birds ; but perhaps their ancestors came from a cooler climate, and have not been able to don a tropical garb ; or perhaps they belong to a far-back age, when the vegetable king- dom also was less rich in colouring than it is at present, and the birds were in harmony with it. This, indeed, seems still to be the character of the Galapagos plants, which Darwin says have " a wretched, weedy appearance," without gay flowers, though later visitors have expressed a more favourable opinion. These plants are in themselves very remarkable, for they are largely peculiar species, and are in many cases confined to par- ticular islands, having apparently been unable to cross from one island to another, though in some way able to reach the group. The explanation is that they resemble North American plants, and came to the Galapagos at a time when a wide strait sepa- rated North and South America, allowing the equatorial cur- rent to pass through, and drift plants to the Galapagos, where they have been imprisoned ever since. This was probably in Miocene times, and when we know more of the Miocene flora of the southern part of North America we may hope to recover some of the ancestors of the Galapagos plants. In the mean- time their probable origin and antiquity, as stated by Wallace, render unnecessary any hypothesis of modification. Before leaving this subject, it is proper to observe that on the continents themselves there are many remarkable cases of isolation of species, which help us better to understand the conditions of insular areas. The " variable hare " of the Scottish highlands, and of the extreme north of Europe, appears again in the Alps, the Pyrenees, and the Caucasus, being in these mountains separated by a thousand miles of apparently impassable country from its northern haunts. It no doubt ex- tended itself over the intervening plains at a time when Europe THE DISTRIBUTION OF ANIMALS AND PLANTS 415 was colder than at present. Another curious case is that of the marsh-tit of Europe. This little bird is found throughout south- western Europe. It reappears in China, but is not known anywhere between. In Siberia and northern Europe there is, however, a species or distinct race which connects these isolated patches. In this case, if the Siberian species is truly distinct, we have a remarkable case of isolation and of the permanence of identical characters for a long time ; for in that case this bird must be a survivor of the Pliocene or Miocene time. On the other hand, if, as is perhaps more likely, the marsh-tit is only a local variety of the Siberian species, we have an illustration of the local recurrence of this form when the conditions are favourable, even though separated by a great space and long time. The study of fossils gives us the true meaning of such facts, and causes us to cease to wonder at any case of local repetition of species, however widely separated. The " big trees " of California constitute a remarkable example. There are at present two very distinct species of these trees, both found only in limited areas of the western part of North America. Fossil trees of the same genus (Sequoia) occur as far back as the Cretaceous age ; but in this age ten or more species are known. Nor are they confined to America, but occur in various parts of the Eurasian continent as well. Two of the Lower Cretaceous species are so near to the two modern ones that even an unbeliever in evolution may suppose them to be possible ancestors ; the remaining eight are distinct, but some of them intermediate in their characters. In the Tertiary period, intervening between the Cretaceous and the modern, fourteen species of Sequoia are believed to have been recog- nised, and they appear to have existed abundantly all over the northern hemisphere. Thus we know that these remarkable Californian giants are the last remnant of a once widely distri- buted genus, originating, as far as known, in the Cretaceous age s. E. 30 41 6 THE DISTRIBUTION OF ANIMALS AND PLANTS Now had a grove of Sequoias, however small, survived any- where in Europe or Asia, and had we no knowledge of the fossil forms, we might have been quite at a loss to account for their peculiar distribution. The fossil remains of the Tertiary rocks, both animal and vegetable, present us with many instances of this kind. The discussion of the distribution of animals and plants, when carried on in the light of geology, raises many interesting questions as to time, which we have already glanced at, but which deserve a little more attention. As to the vast duration of geological time all geologists are agreed. It is, however, now well understood that science sets certain limits to the time at our disposal. Edward Forbes humorously defined a geolo- gist to be " an amiable enthusiast who is content if allowed to appropriate as much as he pleases of that which other men value least, namely, past time " ; but now even the geologist is obliged to be content with a limited quantity of this com- modity. The well-known estimate of Lord Kelvin gave one hundred millions of years as the probable time necessary for the change of the earth from the condition of a molten mass to that which we now see. On this estimate we might fairly have assumed fifty millions of years as covering the time from the Laurentian age to the modern period. The great physicist has, however, after allowing us thus much credit in the bank of time, " sud- denly put up the shutters and declared a dividend of less than four shillings in the pound." 1 In other words, he has reduced the time at our disposal to twenty millions of years. Other physicists, reasoning on the constitution of the sun, agree with this latter estimate, and affirm that " twenty millions of years ago the earth was enveloped in the fiery atmosphere of the sun." 2 Geology itself has attempted an independent cal- 1 Bonney, Address before British Association, 1888. 2 Newcomb, Helmholtz, Tait, etc. THE DISTRIBUTION OF ANIMALS AND PLANTS 417 dilation based on the wearing down of our continents, which appears to proceed at the rate of about a foot in four or five thousand years, and on the time required to deposit the sedi- ments of the several geological formations, estimated at about 70,000 feet in thickness. These calculations would give us, say, eighty-six millions of years since the earth began to have a solid crust, which would, like Lord Kelvin's earlier estimate, give us nearly fifty millions of years for the geological time since the introduction of life. The details of the several esti- mates made it would be tedious and unprofitable to enter into, but I may state as my own conclusion, that the modern rates of denudation and deposit must be taken as far below the average, and that perhaps the estimate stated by Wallace on data sup- plied by Houghton, namely, twenty-eight millions, may be not far from the truth, though perhaps admitting of considerable abatement. This reduced estimate of geological time would still give scope enough for the distribution of animals and plants, but it will scarcely give that required by certain prevalent theories of evolution. When Darwin says, " If the theory (of natural selection) be true, it is indisputable that before the lowest Cam- brian stratum was deposited long periods elapsed, as long as, or probably far longer than, the whole interval from the Cam- brian to the present day," he makes a demand which geology cannot supply ; for independently of our ignorance of any formations or fossils, except those included in the Archaean, to represent this vast succession of life, the time required would push us back into a molten state of the planet. This difficulty is akin to that which meets us with reference to the introduction of many and highly specialized mammals in the Eocene, or of the forests of modern type in the Cretaceous. To account for the origin of these by slow and gradual evolu- tion requires us to push these forms of life so far back into formations which afford no trace of them, but, on the contrary, 41 8 THE DISTRIBUTION OF ANIMALS AND PLANTS contain other creatures that appear to be exclusive of them, that our faith in the theory fails. The only theory of evolu- tion which seems to meet this difficulty is that advanced by Mivart, Leconte, and Saporta, of " critical periods," or periods of rapid introduction of new species alternating with others of comparative inaction. This would much better accord with the apparently rapid introduction of many new forms of life over wide regions at the same period. It would also approach somewhat near, in its manner of stating the problem to be solved, to the theory of "creation by law" as held by the Duke of Argyll, or to what may be regarded as " mediate creation," proceeding in a regular and definite manner, but under laws and forces as yet very imperfectly known, through- out geological time. It seems singular, in view of the facts of palaeontology, that evolutionists of the Darwinian school are so wedded to the idea of one introduction only of each form of life, and its subsequent division by variation into different species, as it progressively spreads itself over the globe, or is subjected to different external conditions. It is evident that a little further and very natural extension of their hypothesis would enable them to get rid of many difficulties of time and space. For example, certain Millipedes and Batrachians are first known in the coal formation, and this not in one locality only, but in different and widely separated regions. If they took be- ginning in one place, and spread themselves gradually over the world, this must have required a vast lapse of time more than we can suppose probable. But if, in the coal-formation age, a worm could anywhere change into a Millipede, or a fish into a Batrachian, why might this not have occurred in many places at once ? Again, if the oldest known land snails occur in the coal formation, and we find no more specimens till a much later period, why is it necessary to suppose that these creatures existed in the intervening time, and that the later THE DISTRIBUTION OF ANIMALS AND PLANTS 419 species are the descendants of the earlier? Might not the process have been repeated again and again, so as to give animals of this kind to widely separated areas and successive periods without the slow and precarious methods of continuous evolution and migration ? This apparent inconsistency strikes one constantly in the study of discussions of the theory of derivation in connection with geographical and geological dis- tribution. We constantly find the believers in derivation laboriously devising expedients for the migration of animals and plants to the most unlikely places, when it would seem that they might just as well have originated in those places by direct evolution from lower forms. Those who believe in a separate centre of creation for each species must of course invoke all geological and geographical possibilities for the dispersion of animals and plants ; but surely the evolutionist, if he has faith in his theory, might take a more easy and obvious method, especially when in any case he is under the necessity of demanding a great lapse of time. That he does not adopt this method perhaps implies a latent suspicion that he must not repeat his miracle too often. He also per- ceives that if repeated and unlimited evolution of similar forms had actually occurred, there could have remained little specific distinctness, and the present rarity of connecting links would not have occurred. Further, a new difficulty would have sprung up in the geographical and geological relations of species and genera, which would then have assumed too much of the aspect of a preconceived plan. It is only fair to a well-known and somewhat extreme European evolutionist, Karl Vogt, to state that he launches boldly into the ocean of multiple evolution, not fearing to hold that identical species of mollusks have been separately evolved in separate Swiss lakes, and that the horse has been separately evolved in America and in Europe, in the former along a line beginning with Eohippus, and in the latter along an entirely separate line, 420 THE DISTRIBUTION OF ANIMALS AND PLANTS commencing with Paleotherium. The serious complications resulting from such admissions are evident, but Vogt deserves credit for faith and consistency beyond those of his teachers. With reference to the actual distribution of species, the question of time becomes most important when applied to the Glacial period, since it is obvious that much of the pre- sent distribution must have been caused, or greatly modified, by that event. The astronomical theory would place the close of the Glacial age as far back as 70,000 or 80,000 years ago. But we have already seen in the chapter on that period that geological facts bring its close to only from 10,000 to 7,000 years before our time. If we adopt the shorter esti- mates afforded by these facts, it will follow that the submer- gences and emergences of land in the Glacial ages were more rapid than has hitherto been supposed, and that this would react on our estimate of time by giving facilities for more rapid denudation and deposition. Such results would greatly shorten the duration assignable to the human period. They would render it less remarkable that no new species of animals seem to have been introduced since the Glacial age, that many insular faunas belong to far earlier times, and that no changes even leading to the production of well-marked varieties have occurred in the post-glacial or modern age. In conclusion, does all this array of fact and reasoning bring us any nearer to the comprehension of that " mystery of mysteries," the origin and succession of life ? It certainly does not enable us to point to any species, and to say precisely here, at this time and thus it orginated. If we adopt the theory of evolution, the facts seem to restrict us to that form of it which admits paroxysmal or intermittent introduction of species, depending on the concurrence of conditions favourable to the action of the power, whatever it may be, which pro- duces new organisms. Nor is there anything in the facts of distribution to invalidate the belief in creation, according to THE DISTRIBUTION OF ANIMALS AND PLANTS 421 definite laws, if that really differs in its nature from certain forms of the hypothesis of evolution. We have also learned that, time being given, animals and plants manifest wonderful powers of migration, that they can vary within considerable limits without ceasing to be practically the same species, and that under certain conditions they can endure far longer in some places than in others. We also see evidence that it is not on limited islands, but on the continents, that land animals and plants have originated, and that swarms of new and vigorous species have issued from the more northern regions in successive periods of favourable Arctic climate. The last of these new swarms or "centres of creation," that with which man himself is more closely connected, belongs to the Palearctic region. We have already seen that in every geo- logical period, when the submerged continental plateaus were pervaded by the warm equatorial waters, multitudes of new marine species appear. In times when, on the contrary, the colder Arctic currents poured over these submerged surfaces, carrying mud and stones, great extinction took place, but certain northern forms of life swarmed abundantly, and when elevation took place, marine species became extinct or were forced to migrate. Everywhere and at all times multiplication of species was promoted by facilities for expansion. The great limestones of our continents, full of corals and shells of new species, belong to times when the ocean spread itself over the continental plateaus, affording wide, untenanted areas of warm and shallow water. The introduction of new faunas and floras on the land belongs to times when vast supplies of food for plants and animals and favourable conditions of existence were afforded by the emergence of new lands possessing fertile soils and abundantly supplied with light, heat, and moisture. Thus geological and geographical facts concur with ordinary observation and experience in reference to varietal forms, in testifying that it is not mere struggle for 422 THE DISTRIBUTION OF ANIMALS AND PLANTS existence, but facilities for easy existence and rapid extension, that afford the conditions necessary for new and advanced forms of life. These considerations do not, of course, reach to the first cause of the introduction of species, nor even to the precise mode in which this may have acted in any parti- cular case : but perhaps we cannot fully attain to this by any process of inductive inquiry. The study of geographical dis- tribution, therefore, does not enable us to solve the question of the origin of specific types, but, on the contrary, points to marvellous capacities for migration and a wonderful tenacity of life in species. In these respects, however, it is a study full of interest, and in nothing more so than in the evidence which it affords of the practically infinite provisions made for the peopling of every spot of land or sea with creatures fitted to flourish and enjoy life therein, and to carry on the great and progressive plan of the Creator. REFERENCES : Continental and Island Life, Princeton Review, July, 1881. Address to American Association, 1883. Papers and Addresses to Natural History Society, Canadian Naturalist, Montreal. "The Story of the Earth and Man," ist ed., 1873, 9th ed., London, 1887. ALPINE AND ARCTIC PLANTS IN CONNECTION WITH GEOLOGICAL HISTORY. DEDICATED TO THE MEMORY OF DR. ASA GRAY, THE GREATEST AND MOST PHILOSOPHICAL EXPONENT OF AMERICAN BOTANY. A BOTANICO - GEOLOGICAL EXCURSION IN THE WHITE MOUNTAINS DISTRIBUTION AND MIGRATIONS OF AL- PINE PLANTS RELATIONS TO THE LATER GEOLOGICAL CHANGES BEARING ON THE VEGETATION OF EARLIER TIMES MOUNT WASHINGTON, FROM TUCKERMAN'S RAVINE, (p. 426.) (After Filmer, in King's " White Hills.") CHAPTER XVI. ALPINE AND ARCTIC PLANTS IN CONNECTION WITH GEOLOGICAL HISTORY. THE group of the White Mountains is the culminating point of the northern division of the great Appalachian range, extend- ing from Tennessee to Gaspe' in a south-west and north-east direction, and constituting the breast bone of the North Amer- ican continent. This great ridge or succession of ridges has its highest peaks near its southern extremity, in the Black Mountains ; but these are little higher than their northern rivals, which at least hold the undisputed distinction of being the highest hills in north-eastern America. As Guyot 1 has well remarked, the White Mountains do not occur in the general line of the chain, but rather on its eastern side. The central point of the range, represented by the Green Mountains and their continuation, describes a great curve from Gaspe to the valley of the Hudson, and opposite the middle of the concave side of this curved line towers the almost isolated group of the White Hills. On the other side is the narrow valley of Lake Champlain, and beyond this the great isolated mass of the Adi- rondack Mountains, nearly approaching in the altitude of their highest peaks, and greatly exceeding in their geological age, the opposite White Mountain group. The Appalachian range is thus, in this part of its course, supported on either side by out- liers higher than itself. The dense grouping of mountains in this region is due to the resistance offered by the old Adiron- 1 Sillimaris Journal. 425 426 ALPINE AND ARCTIC PLANTS dack mass to the westward thrust of the Atlantic and the sub- sequent piling up against this mass of the ridges of palaeozoic sediments. Southward of this the Atlantic thrust has driven these ridges back in a great bend to the westward. My present purpose is not to give a general geographical or geological sketch of the White Mountains, but to direct atten- tion to the vegetation which clothes their summits, and its relation to the history of the mountains themselves. For this purpose I may first shortly describe the appearances presented in ascending the highest of them, Mount Washington, and then turn to the special points to which these notes relate. In approaching Mount Washington by the Grand Trunk Railway, the traveller has ascended from the valley of the St. Lawrence to a height of 802 feet at the Alpine House at Gor- ham. Thence, in a distance of about eight miles along the bank of the Peabody River, to the Glen House, he ascends to the elevation of 1,632 feet above the sea ; and it is here, or im- mediately opposite the Glen House, that the actual ascent begins. The distance from the Peabody River, opposite the hotel, to the summit is nine miles, and in this distance we as- cend 4,656 feet, the total height being 6,288 feet above the sea. 1 Formerly only a bridle path led up this ascent ; but now access can be had to the summit by carriage roads and by rail. These royal roads to the summit are, however, too demo- cratic for the taste of some visitors, who mourn the olden days of ponies, guides and adventures; and though they give an excellent view of the geological structure of the mountain, they do not afford a good opportunity for the study of the alpine flora, which is one of the chief attractions of Mount Washington. For this reason, though I availed myself of the new road for gaining a general idea of the features of the group, I determined to ascend by Tuckerman's Ravine, a great chasm in the moun- tain side, named in honour of the indefatigable botanist of the 1 According to Guyot, but some recent surveys make it a little higher. ALPINE AND ARCTIC PLANTS 427 North American lichens. 1 I was aided in this by the kindness of a gentleman of Boston, well acquainted with these hills, and passionately fond of their scenery. 2 Our party, in addition to this gentleman and myself, consisted of two ladies, two children, and two experienced guides, whose services were of the utmost importance, not only in indicating the path, but in removing windfalls and other obstructions, and in assisting members of the party over difficult and dangerous places. We followed the carriage road for two miles, and then struck off to the left by a bridle path that seemed not to have been used for several years the gentlemen and guides on foot, the ladies and children mounted on the sure-footed ponies used in these ascents. Our path wound around a spur of the mountain, over rocky and uneven ground, much of the rock being mica slate, with beautiful cruciform crystals of andalusite, which seemed larger and finer here than in any other part of the mountain which I visited. At first the vegetation was not materially different from that of the lower grounds, but as we gradually ascended we entered the " evergreen zone," and passed through dense thickets of small spruces and firs, the ground beneath which was carpeted with moss, and studded with an immense profusion of the delicate little mountain wood sorrel (Oxalis acetoselld], a characteristic plant of wooded hills on both sides of the Atlantic, and which I had not before seen in such profusion since I had roamed on the hills of Lochaber Lake in Nova Scotia. Other herbaceous plants were rare, ex- cept ferns and club mosses ; but we picked up an aster (A. acuminatus), a golden rod (Solidago thyrsoidea), and the very pretty tway blade (Lister a cor data), a species 3 very widely dis- tributed throughout British America. 1 Peck, Bigelow and Booth were the early botanical explorers of the White Mountains ; though Pursh was the first to determine some of the more interesting plants, and Oakes and Tuckerman deserve honourable men- tion, as the most thorough modern explorers. 2 Mr. Raymond. 3 L. macrophylla Pursh (Macoun). 428 ALPINE AND ARCTIC PLANTS In ascending the mountain directly, the spruces of this zone gradually degenerate, until they present the appearance of little gnarled bushes, flat on top and closely matted together, so that except where paths have been cut, it is almost impossible to penetrate among them. Finally, they lie flat on the ground, and become so small that, as Lyell remarks, the reindeer moss may be seen to overtop the spruces. This dwarfing of the spruces and firs is the effect of adverse circumstances, and of their struggle to extend their range toward the summit. Year by year they stretch forth their roots and branches, bending themselves to the ground, clinging to the bare rocks, and avail- ing themselves of every chasm and fissure that may cover their advance ; but the conditions of the case are against them. If their front advances in summer, it is driven back in winter, and if in a succession of mild seasons they are able to gain a little ground, less favourable seasons recur, and wither or destroy the holders of their advanced positions. For thousands of years the spruces and firs have striven in this hopeless escalade, but about 4,000 feet above the sea seems to be the limit of their advance, and unless the climate shall change, or these trees acquire a new plasticity of constitution, the genus Abies can never displace the hardier alpine inhabitants above, and plant its standard on the summit of Mount Washington. I was struck by the similarity of this dwarfing of the upper edges of the spruce woods, to that which I have often observed on the exposed northern coasts of Cape Breton and Prince Edward Island, where the woods often gradually diminish in height toward the beach or the edge of a cliff, till the external row of plants clings closely to the soil, or rises above it only a few inches. The causes are the same, but the appearance is more marked on the mountain than on the coast. It is in minia- ture a picture of the gradual dwarfing of vegetation in the great barren grounds of Arctic America. On the path which we followed, before we reached the upper ALPINE AND ARCTIC PLANTS 429 limit of trees, we arrived at the base of a stupendous cliff, forming the termination of a promontory or spur of the moun- tain, separating Tuckerman's Ravine from another deep de- pression known as the Great Gulf. From the top of this precipice poured a little cascade, that lost itself in spray long before it touched the tops of the trees below. The view at this place was the most impressive that it was my fortune to see in these hills. Opposite the mouth of the Great Gulf, and I suppose at a height of about 3,000 feet, is a little pond known as Hermit Lake. It is nearly circular, and appears to be retained by a ridge of stones and gravel, perhaps an old moraine or sea beach. On its margin piped a solitary sandpiper, a few dragon flies flitted over its surface, and tadpoles in the bottom indicated that some species of frog dwells in its waters. High overhead, and skirting the edges of the precipices, soared an eagle, intent, no doubt, on the hares that frequent the thickets of the ravines. Before we reached Hermit Lake we had been obliged to leave our horses, and now we turned aside to the left and entered Tuckerman's ravine, where there is no path, but merely the bed of a brook, whose cold clear water tumbles in a succession of cascades over huge polished masses of white gneiss, while on both sides of it the bottom of the ravine is occupied by dense and almost impenetrable thickets of the mountain alder (Alnus viridis). Tuckerman's Ravine has been formed originally either by a subsidence of a portion of the mountain side, or by the action of the sea. It is, like most of the ravines and " gulfs" of these hills, a deep cut or depression bounded by precipitous sides, and terminating at the top in a similarly precipitous manner. It must at one period have been in part filled with boulder clay, steep banks of which still remain in places on its sides ; and extensive landslips have occurred, by which portions of the limit- s. E. 31 430 ALPINE AND ARCTIC PLANTS ing cliffs have been thrown toward the centre of the valley, in large piles of angular blocks of gneiss and mica slate, in the spaces between which grow gnarled birches and spruces that must be used as ladders and bridges whereby to scramble from block to block, by every one who would cross or ascend one of these rivers of stones. These " gulfs " of the White Mountains are similar to the "cirques" of the Alps, and various explana- tions have been given of their origin. To me they have always appeared to be of the same nature with the " chines " or bays with precipitous ends seen on rocky coasts, and which are pro- duced by the action of the surf on the softer beds or veins of rock. They testify to the raging of the waves for long ages against the sides of what are now lofty mountains. This, we know, must have occurred in the great Pleistocene submergence ; but in mountains so old as those now in question, it may have in part been effected in previous periods. At the head of the ravine we paused to rest, to admire the wild prospect presented by the ravine and its precipitous sides, and to collect the numerous plants that flower on the surround- ing slopes and precipices. Here, on the ipth of August, were several large patches of snow, one of them about a hundred yards in length. From the precipice at the head of the ravine poured hundreds of little rills, and several of them collecting into a brook, had excavated in the largest mass of snow a long tunnel or cavern with an arched and groined roof. Under the front of this we took our mid-day meal, with the hot August sun pouring its rays in front of us, and icy water gurgling among the stones at our feet. Around the margin of the snow the vegetation presented precisely the same appearances which are seen in the low country in March and April, when the snow banks have just disappeared the old grass bleached and whitened, and many perennial plants sending up blanched shoots which had not yet experienced the influence of the sunlight. ALPINE AND ARCTIC PLANTS 431 The vegetation at the head of this ravine and on the preci- pices that overhang it, presents a remarkable mixture of lowland and mountain species. The head of the ravine is not so high as the limit of trees already stated, but its steep sides rise abruptly to a plateau of 5,000 feet in height, intervening between Mount Washington and Mount Munro, and on which are the dark ponds or tarns known as the Lakes of the Clouds, forming the sources of the Amonoosook river, which flows in the opposite direction. From this plateau many alpine plants stretch down- ward into the ravine, while lowland plants, availing themselves of the shelter and moisture of this cul-de-sac, climb boldly upward almost to the higher plateau. Other species again occur here, which are found neither on the exposed alpine summits and ridges, nor in the low country. Conspicuous among the hardy climbers are two coarse and poisonous weeds of the river valleys, that look like intruders into the company of the more dwarfish alpine plants ; the cow parsnip (Herackum lanatuni) and the white hellebore ( Veratrum viride). Both of these plants were seen struggling up through the ground at the margin of the snow, and climbing up moist hollows almost to the tops of the precipices. Some specimens of the latter were crowded with the infant caterpillars of a mountain butterfly or moth. Less conspicuous, and better suited to the surrounding vegetation, were the bluets (Oldenlandia ccerulea), now in blossom here, as they had been months before in the low country, the dwarf cornel (Cornus Canadensis),a.r\d the twin flower (Linn