The disclosures of geology have familiarised us with the conviction that the “stable land,” the “perpetual hills,” and the “everlasting mountains” are but figures of speech. But the idea forces itself on reluctant minds that man himself has witnessed the disappearance of Alpine chains and the submergence of continents. The Pacific archipelagos are but the mountain-crests of a southern continent, which in earlier ages may have facilitated the wanderings of the nations. The startling discoveries in the French and English drift are results of oscillations of the northern hemisphere, which, in times nearer to historic centuries, depressed the bed of the Baltic in the era of the Danish kjökkenmöddingr, and made dry land of the upper estuaries of the Forth and Clyde. It is doubtful, indeed, if the shallowing of Danish and Scottish seas by the rise of their ocean-beds is altogether a work of prehistoric times. The rise still going on in parts of the Swedish coast is a phenomenon long familiar to geologists; and the upheaval of the Scottish region, embracing the valleys of the Forth and Clyde, it now appears probable, has been protracted into historic times, and has even affected the relative levels of sea and land since the building of the Roman wall.
The changes thus witnessed on a comparatively small scale, on familiar areas, help us in some degree to estimate the vast physical revolutions that have taken place throughout the northern hemisphere within that recent geological period which succeeded the formation of the pleiocene strata. One of the most remarkable phenomena now recognised as affecting the conditions of life in recent geological epochs is the prolonged existence, throughout the whole northern hemisphere, of a temperature resembling that of the Arctic regions at the present time. After a period more nearly assimilating in climatic character to the tropics, though otherwise under varying conditions, the temperature of the whole northern hemisphere gradually diminished towards the end of the tertiary epoch, until the highlands of Scotland and Wales—then at a much higher elevation,—resembled Greenland at the present time, and an Arctic temperature extended southward to the Pyrenees and the Alps. Glaciers formed under the influence of perpetual frost and snow descended into the valleys and plains over the greater portion of Central Europe and Northern Asia, and an Arctic winter reigned throughout.
This condition of things, pertaining to what is known as the glacial period, was unquestionably of long duration. But after some partial variations of temperature, and a consequent advance and retrocession of the glacial influences along what was then the border lines of a north temperate zone, the first period of extreme cold drew to a close. Between the Alps and the mountain ranges of Scotland and Wales, the winter resembled that which even now prevails on the North American continent, in latitudes in which the moose, the wapiti, and the grizzly bear, freely range over the same areas where during a brief summer of intense heat enormous herds of buffalo annually migrate from the south. A similar alternation of seasons within the European glacial period can alone account for the presence, alongside of an Arctic fauna, of animals such as the hippopotamus and the hyæna, known only throughout the historical period as natives of the tropics. The range of temperature of Canadian seasons admits of the Arctic skua-gull, the snow-goose, the Lapland bunting, and the like Arctic visitors, meeting the king-bird, the humming-bird, and other wanderers from the gulf of Mexico.
Such conditions of climate may account for the recovery of the remains of the reindeer and the hippopotamus in the same drift and cave-deposits of Europe’s glacial period. The woolly mammoth and rhinoceros, the musk-ox, reindeer, and other Arctic fauna, may be presumed to have annually retreated from the summer heats, and given place to those animals, the living representatives of which are now found only in tropical Africa. A period of depression followed, during which, throughout an extensive area, all but the highest levels was submerged beneath an Arctic ocean, and the drift and boulders of the highlands of Norway and Scotland were dispersed by means of icebergs over the low levels of what was then an archipelago, in which only the higher peaks of Britain rose out of the sea. Far to the south of the Thames and the Seine, the drift of this Arctic ocean was then accumulating the evidence which now reveals to us the fauna and the arts of quaternary Europe; just as the overlying boulders of the American drift far south in the Ohio valleys show their derivation from the Laurentian mountains of Canada. With the elevation of the old ocean-bed there appears to have been a renewal of an Arctic temperature indicated by the traces of local glaciers in the mountains of Scotland, Cumberland, and Wales; and so the glacial period drew to a close. A gradual rise of temperature carried the lines of ice and perpetual snow further and further northward, excepting in regions of great elevation, as in the Swiss Alps. This was necessarily accompanied with the melting of the glaciers accumulated in the mountain valleys throughout the protracted period of cold. The broken rocks and soil of the highlands were swept into the valleys by torrents of melted ice and snow; the lower valleys were hollowed out and reformed under this novel agency; and the landscape assumed its latest contour of valley, estuary, and river-beds.
This is what the elder geologists, including Dean Buckland, accepted for a time as the evidence of the Mosaic deluge. It is now universally recognised as the product of no sudden cataclysm, but the result of operations carried on continuously throughout periods of vast duration, during which the memorials of animal and vegetable life of the pleiocene and pleistocene epochs were slowly imbedded in the accumulated débris of this diluvian reconstruction. The characteristics of the fossil mammals of the post-glacial period differ in many respects so widely from all that we are accustomed to associate with the presence of man, that they help to suggest even an exaggerated idea of antiquity. Nevertheless, there is no break of continuity. Animals still living have their fossil representatives alongside of the pleiocene mastodon, cave-lion, and bear: if indeed the latter be not itself the ursus ferox, or grizzly bear of North America, the claws of which are still worn as the proudest trophy of the Red Indian hunter.
Of twenty-one species of post-glacial mammals identified in the deposits of Brixham Cavern, only four are regarded as extinct species, and these include the ursus spelæus and hyæna spelæa. But their habitats have been widely changed in the climatic and geographical revolutions which have intervened. Some have to be sought for within the Arctic circle; others in low latitudes, and on continents lying wholly outside of that world which was alone known to Aristotle and Pliny. Every thing indicates a revolution slowly wrought through unnumbered ages, during which the ancient fauna was being supplanted by novel species, including those which belong to the historical period of temperate Europe. So far as appears from present evidence, man himself has to be included among the new additions to the European fauna. To this post-glacial period must, at any rate, be assigned the advent of the Flint-Folk of the Drift: a race of hunters and fishers not greatly differing in their rude arts from the more immediate precursors of the Historic races in Europe’s Stone Age; but who were contemporaneous with the Siberian mammoth and other extinct elephants, the woolly rhinoceros, the musk-ox, and the reindeer of France; and with numerous extinct carnivora of proportions corresponding to the gigantic herbivora on which they preyed.
The regions in which remains of the Flint-Folk have hitherto chiefly occurred embrace the valleys of Northern France and Southern England, where now the vine and the hop clothe the sunny slopes with their luxuriance. But as fresh evidence accumulates, corresponding indications are found to extend to the shores and islands of the Mediterranean. Traces of Europe’s neolithic artificers have been found in the caves of Gibraltar; and among a singularly interesting accumulation of flint-flakes, polished stone axes, rude pottery, etc., lying beside the skeletons of their owners, in the same caves of Andalusia from one of which a golden tiara of primitive workmanship has been recovered.[[9]] Among remoter traces in the Maccagnone, Sicilian cave, Dr. Falconer could discover nothing suggestive of a different period for the rude flint implements and the numerous bones of the hippopotamus, mammoth, cave-lion, and other fossil mammals with which they were conjoined; while far eastward, near Beyrout, the Rev. H. B. Tristram reports the occurrence, in the stalagmitic flooring of a limestone cave, of bones and teeth assigned to a fossil ox, the red-deer, and the reindeer, alongside of the flint-knives or flakes which the prehistoric cave-men of Lebanon had used when feasting on such prey.[[10]] But though such traces occur on ancient historic sites, we search in vain for any connecting link between the oldest historic races and those belonging to an era which one distinguished geologist has designated as “The Second Elephantine Period”;[[11]] when, according to his reconstruction of the physical geography of the region, the Thames was a tributary of the Rhine; the English Channel was not yet in being, and Britain existed only as part of a continent which stretched away uninterruptedly northward towards the Arctic circle.
It thus appears that the advent of man in Northern Europe is assignable to a period when the mammoth and the tichorine rhinoceros still roamed its forests, and the great cave-tiger and other extinct carnivora haunted its caverns; when the gigantic Irish elk, the reindeer, the musk-ox, and the wild horse were objects of the chase; and the hippopotamus major was a summer visitor to the Seine and the Thames. When first employing the term prehistoric which has since obtained such universal acceptance, I remarked, in reference to Scottish aboriginal traces: “There is one certain point in this inquiry into primitive arts which the British antiquary possesses over all others, and from whence he can start without fear of error. From our insular position it is unquestionable that the first colonist of the British Isles must have been able to construct some kind of boat, and have possessed sufficient knowledge of navigation to steer his course through the open sea.”[[12]] It then seemed a postulate on which the most cautious adventurer into the great darkness which lies behind us might confidently take his stand. But the point was no certain one after all. The fauna of the later Elephantine period still roamed over a wide continent unbroken by the English Channel or the Irish Sea; and the valley of the Rhine stretching northward through the still unsubmerged plain of the German Ocean, received as tributaries the Thames and the Humber, perhaps also the Tweed and the Forth. Measured therefore by the most moderate estimate of geological chronology, the historical period is, in relation to the interval since the first appearance of man, somewhat in a ratio with the superficial soil and vegetable mould, as compared with the whole deposits of the stratified drift: in other words, it is so insignificant as, in a geological point of view, to be scarcely worth taking into account.
Whatever be the consequences involved in such comprehensive inductions, proofs appear to accumulate, with every renewed search, of the wide diffusion throughout the bone-bearing drift of the post-glacial period, of symmetrically-formed flints, bearing indubitable traces of intelligence and primitive mechanical skill.
It is the old argument of Paley, reproduced in a form undreamt of in his philosophy. “If,” he might have said, “in digging into a bank of gravel we find a flint, we do not pause to ask whence it came; but if our spade strike on a watch?”——In the age of the Flint-Folk mechanical ingenuity expended itself for other purposes than the manufacture of time-measurers; but if the artificial origin of the implements of the drift, and their consequent indications of the presence of man, be acknowledged, our greatest difficulty is the remoteness of the period which they seem to indicate. Worked flints and other assumed human industrial remains have now been recovered from caverns, in various countries of Europe, as in the caves of Engis and Chokier, near Liége; at Mont Salève, Geneva; in the south of France, in Belgium, and in England: in every case so mingled with remains of the mammoth, rhinoceros, hyæna, and other extinct mammals, as to lead to the conviction of their contemporaneous deposition. Recent carefully conducted explorations in the Devonshire caves have resulted in seemingly indisputable proof that English flint-implements of the Amiens type are coeval with the extinct fauna; and that consequently the presence of their manufacturers must be assigned to periods prior to the successive inundations and depositions by which Brixham cave was gradually filled with layers of water-worn gravel, silt, or cave-earth, bone breccia, and solid floorings of carbonate of lime.