PRE-DETERMINATION IN NATURE.

Rusichnites Grenvillensis, Billings a "Bilobite." Probably the Cast of a Crustacean burrow.

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 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 anterior 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 indications, 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.[150]Nor does it seem 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 doctrine of Footprints.

[150]Geologists are greatly indebted to Dr. Nathorst of Stockholm for his painstaking researches of this kind.

I have said nothing of true Algæ 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 seaweeds and land plants drifting in currents, some of which are very curious and fantastic; nor of those singular trails referred to the arms of cuttle-fishes 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 ofvertebrate animals having limbs, the information we can obtain is of a far more definite character. This has already been referred 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 proportions. 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 sandstones 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 imperfections of our geological record, or at least of pointing out gaps which but for them we might not have suspected. The remarkableinferences of Matthew already referred to, respecting cuttle-fishes 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 Imitative Markings,Amer. 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.

DEDICATED TO THE MEMORY OFELKANAH BILLINGS,First Palæontologist ofthe Geological Survey of Canada,who laid the Foundations of our Knowledgeof 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 Trilobites—In the Skeletons of Sponges—In Early Vertebrates—In Plants Laws of Fixity and Diversity

Restoration of Protospongia Tetranema.Quebec group; Siluro-Cambrian, Little Metis (p. 335).

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 experience dispels this delusion, and perhaps replaces it with an opposite error. When our minds have been familiarized with the continuous processes by which vaporous nebulæ 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 perpetual 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 determinateadditions, 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 originally 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 submergence 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 continuity 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 wehave 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 marginal 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 currents 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 theChallengerreports, 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 continents by the argument that they are needed to furnish the materials of marginal mountains which are due to the continuous sweeping of arctic material to the south by currents, as we see in the coast of North America to-day. Nor do we invalidate 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 illustrated by Matthew,[151]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 connection in the West Indian region at two distinct periods of time (the Lower Cretaceous and the Miocene Tertiary). Butbridges 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 consequences to its inhabitants.

[151]Transactions Royal Society of Canada, 1892.

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 particularly 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.

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 permeate and pass through the skeleton, and that the protoplasmic 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 determinations 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 existence of this ancient animal would be impossible. Yet how much is implied in all this, and though nothing is more unstable chemically or vitally than protoplasm, if it were introduced 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 conditions of an external articulated skeleton had been finally settled. The material chitinous or partly calcareous, its microscopic 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,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 described; 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 present 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, justas 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 cuttle-fishes and the true fishes. The same rivalry existed in the oldest seas, when the competition 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 successors. I have myself described[152]a carboniferous fish (Palæoniscus) 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 replaced by calcite, showing even that like the lens of the eye of a modern fish it had been constructed of concentric laminæ. In the Carboniferous period also, both types of eye, the compound and the single, experienced the further modificationsnecessary to fit them for vision in air, the compound eye in insects, the simple eye in Batrachians.[153]The original photographic 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.

[152]Canadian Naturalist.[153]Seeante, chapter on Air-breathers.

[152]Canadian Naturalist.

[153]Seeante, chapter on Air-breathers.

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 theChallengerhave 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,[154]have perfected those arrangements of ciliated cells in chambers and canals which the microscope shows us driving currents of water through the modern sponges, and thereby bringing to them the materials of food and means of respiration. It is true we know as little as the sponges themselves of themodus operandiof those perpetually waving threads which we call cilia or flagella, yet they must have existed with all their powers even before the Cambrian period.[155]

[154]I have found spicules of sponges in the chert nodules from the Huronian limestones of Canada.[155]Many species of hexaclinelled sponges 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.

[154]I have found spicules of sponges in the chert nodules from the Huronian limestones of Canada.

[155]Many species of hexaclinelled sponges 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.—Palæosaccus Dawsoni, Hinde.From the Quebec group (Ordovician), Little Metis, Canada.Reduced to 3/7 the diameter.(From theGeological Magazine, 1803.)

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 cross-like 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 andtransverse 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 likechevaux de frizeat 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 themselves 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 (Hexaclinellidæ) 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 (Lithistidæ), constructing skeletons of carbonate of lime, and which preferred, instead of the regular mechanical structures 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 withaltogether 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 improvement, 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 aërial 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-developed, 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 thanfour 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 ofSauropus unguifer, or the reflexed little toe ofCheirotherium, 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 marvellous 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 instrumental 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 sustenance.

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 thickening 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 themore 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 Lingulæ, 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 disappeared, and have been replaced by new types.

We began this chapter with a consideration of the permanence 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 offorce just as much as in natural laws; and that while God has made everything beautiful in its time He has also made everything 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.

DEDICATED TO THE MEMORY OFMY LATE FRIENDDAVID MILNE HOME, LL.D., F.R.S.E., ETC.,An eminent and judicious Advocate of sound andmoderate Views respecting the Glacial Age.

Exaggerated Ideas—The St. Lawrence Valley—Modern Ice Action in the St. Lawrence—Coast Ice—The Icebergs of Belle-Isle—Mt. Blanc and its Glaciers—Effects of Glaciers—Possible Extension of Glaciers—Facts of Glaciation in Canada—Cordilleran 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

Modern Boulder Beach.—Little Metis, St. Lawrence Estuary. (From a Photograph.)Showing the manner in which travelled boulders are piled up against the beach by the floating ice of the Modern time (p. 346).

THE GREAT ICE AGE.

Scientific superstitions, understanding by this name 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 indicatedby 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 important 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. Fortunately 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 steadfast 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.[156]

[156]I may refer here to the recent researches of Dr. G. M. Dawson, Mr. R. Chalmers, Mr. McConnell and Dr. Ells.

The writer of these pages has, ever since the publication of the first edition of his "Acadian Geology,"[157]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 thecourse 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 formidable continental glacier broken up into great local glaciers on the mountain ranges separated by intervening areas of submergence.

[157]1855.

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,[158]and some general deductions as to glacier possibilities.

[158]Published in 1867.

A scientific voyager carries with him a species of questioning 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 havea 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 extending 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, morethan 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 ofice and boulders up the river from the north-east, the latter show evident signs of the movement of local 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 glistening 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.

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 different 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 accumulations 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 30th 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 imagine four hundred of them moving up and down under the influence 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 conception 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, theymove 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 accumulations 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 striæ 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 thischannel 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 appearance of stones and dead shells taken up from the banks off the American coast, and am convinced that an erosive power comparable to that of a river carrying sand over its bed, and materially aided by the grinding action of ice, is constantly in action under the waters of the Arctic current.[159]The unequal pressure resulting from this deposition and abrasion is not improbably 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, constituting 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 thousands of feet of deposits which now constitute the great range of the Alleghany and Appalachian 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.

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