Part 9

The same tale is told by the coal-measures. Dr. Dawson, of Montreal, has drawn out the argument from the carboniferous formation[57] with extraordinary force and a convincing plainness that leaves nothing to be desired, for the benefit of any one who will read his great work on Acadian geology. The formation of coal depends on sub-aërial growths, affected by sub-aqueous action. The trees and plants, out of which coal is formed, for the most part could not possibly have grown under water. The mud, the sand, the stone which cover seams of coal, could not have been laid over them without the agency of water to bring them down, and spread them out in regular layers of stratification. When the hollow bark of a tall tree is found erect upon its roots, with those roots still permeating the clay from which they once drew nourishment, it is evident that time must be allowed for the growth of the tree, for the almost complete decay which left nothing of it but its bark and roots, and for the slow accumulation of sediment which has encased without overthrowing it. A complete alteration must have taken place in the conditions of the ground in the interval between the time when the tree began to grow, and the time when a length of seven or eight feet of its upright stem was buried in mud. Layers, indeed, of sand and mud may be spread out over small areas by storms and inundations with comparative speed; but if above the sands we come to thicknesses of limestone composed almost entirely of animal remains, such as those of shells and fish, not only are we forced to admit a long period for the successive generations of those creatures, but we are forced to observe the products of the ocean lying actually above the products of the dry land, as though, according to the old poetical extravagance, the stag and doe had taken to the waters and the fishes been building in the tree-tops. The conclusion is inevitable, that what was once dry land, fruitful in vegetation, in process of time became a swamp, and from the swamp became a sea. It will be a fresh surprise, but a fresh evidence of time’s duration, if above the limestone we find more clay with more plants buried in more mud, and over-topped by more limestone. Bearing in mind the old supposition, that order and beauty and life upon the globe are only six thousand years’ old, astonishment should reach its climax when we find, as we do, that within the thickness of only a few feet of the earth’s crust, the record that we have been describing is repeated again and again and again; but beyond the climax, a fresh and overpowering marvel awaits us, when, as at one spot in British America, the record expands itself from a few feet into sixteen thousand, showing conclusively by eighty successive bands of coal that fourscore times at least, and perhaps many more, while that thickness of the earth’s crust was forming, the waters gave place to dry land, and in turn the dry land to the waters,--showing conclusively that during all the period of these changes tall forests of graceful trees abounded on the globe, along with exquisite ferns and curious reptiles, and beetles and winged insects of great size and beauty; while fish replenished the waters, along with an infinity of shells and corals, and other inhabitants of the deep. Yet these sixteen thousand feet, these eighty successive forests, these hundred and sixty changes, comprise but a small fraction of the whole known succession of strata.

It is true that different strata not only may, but must have been forming at one and the same time in different parts of the world. But when one stratum has been formed out of the wreck of another, it is self-evident that they cannot have been formed together. The same thing is obvious in regard to any number of layers found lying in undisturbed succession one above the other. They must have been formed successively, the lowest first, the highest last. But one point about them is far from obvious, namely, the length of the interval that may have intervened between the end of one formation and the beginning of another. The great African desert has been the great African desert as far back as human histories extend; yet in times geologically recent it lay beneath the waters of the ocean. Should it be again submerged before any fertilizing agencies have covered it with signs of its sub-aërial exposure, another layer of sand may be thrown down upon it, containing new marine fossils, and no memorial be left to the future geologist of the vast era during which its kindly influence was warming the winds of Europe, and saving us from a glacial climate. The ground you stand on is passing through such an interval. It was under the sea once; doubtless it will be under the sea again in the future. Look into that future; look into that past. Can you measure either of those intervals in the years of common chronology? Yet all over the world the succession of geological strata proclaims the recurrence over and over again of such intervals; silent, indeed, as to positive evidence, but widening the possible limits of time’s duration to the furthest stretch of fancy.

All our great continents have been ever so many times, either in the mass or piecemeal, under the waves of the ocean. Nothing hinders that the bed of every great ocean should have been ever so many times turned into dry land. This interchange is going on now in numberless regions of sea and land. All the facts as we find them are such as they might be expected to be had this interchange been going on, as no doubt it has been, through an indefinite past. We are bound to allow millions of years for the formation of the strata that have been already examined. There may be depths below the lowest depths yet explored by geologists; there have certainly been immense intervals which have left no materials for the geologist to explore; and when all the profoundest deep of stratification shall have been explored, we may still find that the record of all these unnumbered millions of years is but, as it were, the latest page of the volume--a page that may have been preceded by a thousand others now almost irrevocably lost or become utterly illegible. There is nothing to hinder the supposition that those earlier pages, if they existed, were, amidst innumerable differences, still in their general aspect very like the latest, as long or longer, as full of the memorials of eventful circumstance, of constant change dominated by and springing from the operation of unchanging laws. As the time is absolutely incalculable which the theory of evolution requires to account for the highest forms of life upon the earth, so the time which all these considerations leave open for the work is absolutely beyond calculation. The theory cannot ask for more than the facts make it possible to offer.

We hear men sometimes dwell on an expression which they fancy to be Scriptural, ‘that there should be time no longer[58];’ as if time by any possibility could ever come to an end! It is a pity that they should completely misinterpret the passage on which their opinion fancies itself to be grounded. It is a still greater pity that they should use the language of rational human beings, without being at the pains to determine whether their words have any intelligible meaning: for certainly to the human mind any beginning or end of time is wholly inconceivable. Language itself will not bear with the conception, unless it be consistent to speak of a _time_ when time was not, of a _time_ when time will be no more.

There is a poem, and a sweet one, by the present Poet-Laureate, in which the murmuring brook is made to speak the language of the moralist, and to proclaim the transitory nature of all human affairs, by a comparison between the short duration of man’s life and its own unceasing current--

‘For men may come, and men may go, But I flow on for ever.’

Such is the proud language of the murmuring brook. Yet the boast is an untrue one; for if any conclusion in regard to the future can be warranted from the facts of the past, none can be more sure than that no particular brook will flow on for ever. Instead of a brook, it may become a mighty river like the St. Lawrence; it may dash over precipitous cliffs with a vaster fall and volume than Niagara; and, after all, the slow inexorable changes of the earth’s crust will one day make its flow impossible, and the channel of it shall know its stream no more. Only the flow of time is unending, of time which does nothing, but out of or without which nothing can be done,--of time, replete with glorious wonders as far back as the knowledge or the imagination of man can penetrate, through every age, through every million of years that can be rescued from forgetfulness, bearing fresh testimony, in the greatness and the endlessness of the work, to the eternal power and wisdom of the Supreme Worker.

NOTE ON THE HYPOTHESIS OF SPONTANEOUS GENERATION.

Presuming that there is not a particle of evidence as yet established in favour of the supposition known as the doctrine of _abiogenesis_, it does not follow that no such evidence ever will, or ever can, be forthcoming. The advancement of science is continually doing away with harsh, abrupt outlines, and revealing the softest shades of transition in the varied scenery of nature. Between organic and inorganic matter, between the inert and the living mass, the line of separation has been hitherto, to our minds, the hardest and sharpest of all. We have indeed become so accustomed to this violation of the cosmos, this harsh interruption to the continuous order of nature, and to the simplicity of its general plan, that we are apt to be rather annoyed than pleased with the first efforts made to prove them only imaginary. There is a dignity about life which requires, it is thought, to be defended from too close a proximity in character to the chemical solids and liquids amongst which it makes its appearance, even though the life whose dignity is thus maintained exhibit little more than the functions of a stomach, or be presented in the somewhat dull animation of a chrysalis and the torpor of a slug.

A _Wellingtonia gigantea_, with its stupendous height and graceful form, with its bark and wood, and sap and pith, and cones and innumerable spikelets, seems wonderfully noble and vastly superior in the scale of creation to a spoonful of salt; yet every one of the tiny grains has, so far as we know, full as much sense and as much power of enjoyment as the stately tree. The mineral and the vegetable are, in fact, alike destitute of any qualities on which a comparison of dignity can properly be founded. The organic depends ultimately upon the inorganic for its nutriment. It is itself ultimately reduced to the inorganic. It does not, therefore, seem incredible that living organisms, simpler perhaps than any yet detected by the microscope, should be or should have been produced without generation proper by the mere combining of inorganic materials.

This is the hypothesis of Spontaneous Generation, so called, or _abiogenesis_, unproved and extremely difficult of proof, but precisely filling that gap in the order and continuity of nature which is so puzzling without it.

Practically it makes no difference to the theory of development whether the simple organisms from which that theory supposes the more complicated to be derived, originated at a single era or at several. The theory does not deny the perpetuation throughout vast ages of extremely simple organisms. To the general cohesion of the theory, therefore, it is unimportant whether we affiliate each of these living motes to a parent like itself, or to a combination of chemical substances previously without life.

Considering the vast results attributed to the principle of _variability_, it has been thought strange that any organisms should through great cycles of time have escaped its operation, and transmitted their original simplicity to an endless succession of descendants.

On the hypothesis of spontaneous generation working continuously this difficulty would disappear; simple organisms would be continually losing their simplicity by variation, but new organisms of equal simplicity would continually appear in the world, spontaneously generated.

It might still be true that all but the least conspicuous members of the world’s population belong to a single family, or to an extremely small number of separate lines of descent. If we suppose that, as soon as the globe was fitted for living occupants, a single simple organism was spontaneously generated, or, if you please, created, or, in any other way that may be named, introduced upon the earth, the results in accordance with actual facts may be logically deduced agreeably to the various principles of the theory of development. Its descendants would multiply and replenish the earth, unchecked, in all parts suited to their conditions of existence, till all such parts were occupied. No further advance in the population of the world could then take place until some variation had occurred, making possible the occupation of new regions, or of the old regions, under new conditions. But the new species, constituted by some advantageous variation, would be likely to overrun the whole field, to the almost complete suppression of the earlier and more simple form. The distance thus gained in the race of progressive organization it would be likely not only to maintain, but greatly to increase. Its descendants would vary in more than one useful direction, till it might, as we have said, become the parent of all the conspicuous members of the earth’s population. The earliest and simplest form might still have representatives inheriting its likeness by direct descent, but unable to make their way in the world, not from wanting the power to vary, but from finding the world pre-occupied by species too powerful for them to compete with. In this way they would be restrained to their original insignificance.

Now exactly the same result would follow, if, instead of being born in what we consider the ordinary course of parentage, these simple forms were ever being spontaneously generated. They would find the world pre-occupied against their advancement in the scale of organization; they would rarely, if ever, be allowed to lead up by successive useful variations to highly organized forms; and if ever, only in periods of time so enormous as to perplex the acutest human understanding.

What is commonly supposed to be the Biblical theory of Creation, is in truth a theory of spontaneous generation, only multiplying a million-fold the difficulty, if it be a difficulty, involved in that hypothesis. Unless we suppose the globe to have always existed, and always to have been tenanted by creatures endowed with life, we are forced to believe in the occurrence at some time or other of what, in the language of science, must have been spontaneous generation. As there is no historical reason for confining such an occurrence to any particular era; as science can give no reason why, if it happened once, it should not happen an indefinite number of times; as all analogy is in favour of uniform laws of nature rather than exceptional surprises; and, lastly, as numerous phenomena that have to do with the reproduction and maintenance of life are all continuous, and not interjectional--it seems at least an open question whether the origin of life itself may not also be sometimes, or even continually repeated. For, imagine what conditions we will to have prevailed when the elementary substances coalesced, out of which were compounded the first living being, it is difficult to imagine that the same conditions should never have recurred to produce a similar result, since the conditions are so far limited, that they must have been consistent, not only with the birth, but with the life after its birth, of that most antique animalcule. So many wonderful and hitherto unsuspected effects in the working of Nature have of late years been unveiled, so much of marvellous analysis successfully carried out, that it would surely be superstitious to despair of finding fresh links in the chain that binds together the lifeless and the living. Experiments in this direction may hitherto have failed from want of skill or care, or proper means at the command of those who conducted them. Yet it is not too much to ask of men renowned in science, that in pointing out the errors, they should abstain from discouraging the efforts.

Let it not be thought irreligious to anticipate the possible establishment of the supposition now under discussion. It cannot be irreverent to think that the bestowal of life upon a particle of matter too minute for human eye to see, requires no more special apparatus than that allotted to the exquisite crystals of the frost. ‘Out of whose womb came the ice? and the hoary frost of heaven, who hath gendered it?’ Yet in the workmanship of these a Divine hand is to the full as visible as in a diatom or a puff-ball. That the life-giving energy should have been exhausted in a single effort, is contrary beyond doubt to the analogy of religion, whatever may be thought of the analogy of nature.

On the other hand, let it not be thought unscientific to advocate the claims of an unproved hypothesis. It is the nature of hypotheses to be unproved. As they gather proof, the hypothetical becomes a theory. At length the theory goes on to demonstration. The use of hypotheses has often been explained. The human mind is easily exhausted by the observation of numerous incoherent facts. It is impelled to arrange and classify, to find some thread or threads of association on which the facts may be strung, some principle on which they may be parcelled out into groups. The arrangement may be erroneous, the explanatory principle untrue; they may be so plausible, so apparently satisfactory, so fascinating withal in general aspect, as for a long time to hinder the real solution of great problems; and nevertheless it may be judged that their services in the advancement of knowledge far outweigh the hindrances caused by the too servile acceptance accorded them. The foibles of a great writer may long infect the literature which his greatness has ennobled. A constitution grandly conceived in proportion to the moral and social ideas prevailing at the time of its conception may be clung to with servility long after it has been outstripped by the progress of civilization. But neither the genius of the poet nor the skill of the lawgiver could be spared in its own day and generation; neither could have been sacrificed to prevent the follies of the plagiarist, or the dulness of eyes that in after ages might read the letter without discerning the spirit.

We may almost say that a bad hypothesis is better than none; but a wrong hypothesis need not be a bad one. It may tend so to group around it the facts contributed by supporters and opponents, that when the real explanation of them all comes to be suggested, the fraternization of the confronting armies may be easy, and the truth be greeted and acknowledged with general acclaim.

THE IMPERFECTION OF THE GEOLOGICAL RECORD.

The general who is for ever counter-marching and skilfully executing retrograde movements cannot always sustain the enthusiasm of his own troops, much less excite in his favour that of the civilian multitude. To many minds, the reliance placed on the imperfection of the geological record appears to be a rather damaging retreat in the strategy of science. They were just beginning to believe in geology as a wonderful revelation of the past history of the globe, when suddenly they are told that the fragments of that history which have been saved are merely tattered pages out of different chapters, giving no adequate notion of the enormous bulk and varied contents of the whole volume. Since, without the geological evidence of time’s duration and of the countless changes in organic structures which that duration embraces, the theory of development could never have been imagined, it seems half ungrateful and inconsistent in the author of the theory to turn round upon geological evidence and tax it with its extreme poverty and even delusive misleading appearances. But, in fact, Mr. Darwin in no way detracts from the value of geological evidence. The researches necessary to extend it are invested, to those who accept his theory, with tenfold interest. The deficiencies and interruptions in it which he has pointed out as necessarily occurring must sooner or later have become apparent. They were dangerous to science only as long as they were unobserved, or not sufficiently taken into account.

That the record is really imperfect is not a matter which admits of controversy. No one supposes that every species and variety that ever existed in past ages on the globe is represented at this very day by fossil specimens in prime enough condition to exhibit all the characteristics of the creature as it once lived. No one supposes that, if such specimens existed, all of them ever could or would be found by human beings. It is not in the nature of a fossil to present all the characteristics of the creature as it once lived. It cannot possibly do it; for the fossil is without life and motion. There is no respiration, no circulation of the blood going on. As a rule, only the hard parts of the creature, such as shell, scales, or bony skeleton, can be preserved. In most cases all these relics have been chemically altered. Nevertheless, in fossils from the very lowest strata, from the very earliest formations that yield any, we find certain analogies to creatures now living. We reason from these analogies without any hesitation to the characteristics which the fossil creature will probably have presented in its living state. Our reasonings may often be erroneous, but the mere fact of our accepting the apparent analogies as a ground for reasoning at all, implies a belief in the uniformity of the conditions of animal existence between our own times and the most distant ages of the past. We argue as if generation had succeeded generation without interruption, not as if there had been new independent creations from time to time, since these would imply new conditions replacing the old, and make the argument from analogy between the items of the different creations of no value. For these independent creations, whether capricious or not in themselves, could only exhibit to our minds the symptoms of caprice. The mere fact of their being independent one of another would be so wanting in congruity with all the rest of our experience, that we should reasonably expect their minor details as well as the general plan to be wholly fantastic. In other words, the fossil memorials of life in past ages, imperfect as we confess and maintain them to be, still present so many general resemblances to one another and to living structures of the present day, that if they do not prove the continuity of life upon the globe, they cannot be held to prove anything at all; they should be regarded as a very elaborate practical joke played upon the human reason.