It is not uncommon to find fossils in the pebbles of a conglomerate rock showing lines of a dislocating fracture filled with spar. The fossil shell or coral once had an inhabitant. We must allow time for its life and death. Its vacant tabernacle must then have become filled with extraneous matter. This must have required time to harden into rock. While that rock was still in the mass, some cause must have operated to fracture it, and such causes are not of every-day operation. After this, more time was needed to fill up the divisional line with spar; more time to break off the fragment containing the shell from the general mass of the rock; more time to roll it into a pebble; more time to imbed it hard and fast in a conglomerate rock; more time to raise the rock high out of the waters; and, lastly, one more vast addition of time for the crumbling away of the conglomerate formation, so as to expose the tall sea-cliff from which human hands might gather this memorial relic of untold ages.
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.