“According to this theory, the Solent was at that time an estuary somewhat like the Southampton Water, having but one opening to the British Channel, but of so much more importance than the latter as it was fed by a vastly greater flow of fresh water.” “Of course, according to this view, the sea would lose its original condition as an estuary at the time when the British Channel had so far made a breach through the chain of rocks connecting the Isle of Wight with Dorsetshire as to give an opening into itself for the Dorsetshire rivers, somewhere opposite to the town of Christchurch. From that time forth the Solent would become what it is at present, losing its character as an estuary, and assuming that of a long narrow sea.” . . . “The distant period at which such changes took place it would be hopeless to guess at, amid the dimness of the data on which calculations could be founded. It could not be less, however, than many thousands of years, seeing that since that time, the British Channel has not only made a broad breach of twenty miles through a chain of slowly yielding rocks, but has also pushed its way gradually across the broad extent of the Poole and Christchurch Bays.”
Such is the theory of Mr. Fox, which places the probable course of events fully and fairly before our view. I see in it but little on which to comment, except that it does not appear to have sufficiently taken into account the widening of the Solent subsequently to the time of its becoming a channel of the sea; and that in a passage, which I have not quoted, Mr. Fox estimates the drainage area of the ancient river as but little inferior to that of the Thames or Humber. Taking the basins of all the streams discharging{692}into the sea between Ballard Down, near Poole, on the west, and Calshot Castle and the Medina on the east, but not including the latter river, I find that, according to the Ordnance Map,[2781]the present land area which would have drained into an ancient river such as that supposed, is 1,617 square miles. To this may be added another 100 square miles, representing the area included between the present coast and an extension of the chalk downs from Ballard Down to the Needles, the whole of which has been washed away; though within this large area, the present depth of the sea attains in but very few places to ten fathoms. The drainage area of the ancient river Solent can therefore have been but about one-third of that of the Thames and its affluents, unless we are to suppose that, as is the case in the neighbourhood of Carisbrooke Castle and with the Medina, a portion of land to the south of the old chalk downs drained northward through some gap in the range of hills. That such land existed seems probable, from the occurrence of gravels with elephant remains along the south-west coast of the Isle of Wight at an elevation of 80 feet and upwards above the sea, which, Mr. Codrington has suggested, may have been deposited by tributary streams of a river flowing northwards through the chalk range to the Solent. But even with any such addition the area drained by the old River Solent can hardly have been half that of the basin of the Thames.
With regard, however, to the former existence of this range of chalk hills and the land to the north of them, Mr. Codrington has shown, in the paper already so often quoted, that the spreading out of the marine gravel, and the levelling of the table-lands was probably effected in an inlet of the sea, shut in on the southern side by land which connected the Isle of Wight with the mainland, and opening to the eastward. Assuming, then, the existence of this ridge of high land, it is evident, as Mr. Fox has pointed out, that the only outlet for the rivers now represented by the Frome, the Trent or Piddle, the Stour, Blackwater, Avon, and other streams now discharging into the sea, must have been by an eastward channel, in fact, a continuation of the rivers now discharging through Poole Harbour. The course of such a river would naturally be guided, in the first instance, by the configuration of the surface of the old marine gravels of the sloping table-land. This, as has been shown, slopes upward from the present coast northward, and attains its highest level inland; but traces of the same gravel occur also in the Isle of Wight, though it there{693}slopes upward in a southerly direction, attaining a height of 368 feet at St. George’s Down, but being only from 100 to 160 feet above the sea in various places along the northern shore of the island, at a distance of about a mile inland. It appears, therefore, that there must originally have been a valley running east and west in the old marine gravel, forming a natural course for the drainage of the country, and probably finding its way towards the sea, somewhere within the space now occupied by the Solent and Spithead, though not actually discharging into the sea until it had attained some distance eastward.
Evidence as to the highest level at which freshwater action removed and re-deposited the marine gravel on the southern slope of the valley is at present wanting; but, judging from a section across the Isle of Wight from St. George’s Down to Norris Castle, given by Mr. Codrington, the declivity is so much more rapid below the 160 feet level than above it, that the ancient river may have commenced its action at about that level. How far eastward the Isle of Wight may have extended at that time it is difficult to say; but from the enormous denudation of land to the west, and the range of the ten-fathom line, there may probably have been land at all events as far east as opposite to Selsey, the extensive estuarine beds at which place, containing remains ofElephas primigenius,[2782]are possibly connected with this old river.
The precise manner in which the Foreland gravels and brick-earth, in which Mr. Codrington found a palæolithic implement at 85 feet above the sea-level, were connected with the old river-deposits, is difficult to determine. Mr. Codrington is inclined to think that a rise of land to the extent of 70 or 80 feet must have taken place since the deposition of the brick-earth in which the flint implement was embedded, but this to me seems unnecessary. It is, however, unsafe to speculate on a single specimen found in such a position. The implements found at Seaview and Bembridge may have been washed out of gravel-beds at a lower level than those of the Foreland, or even have been transported for some distance by marine currents.
Turning to Bournemouth, where so many more have been found, the highest and most westerly point at which implements have occurred appears to be about 130 feet above the sea.[2783]Farther{694}east, near Boscombe, the level is about 120 feet; midway between that spot and Hengistbury Head, the height of the gravel is 90 feet; at High Cliff, 84 feet; at Hordwell, where implements abound, a short distance inland, 60 feet; and about midway along the northern shore of the Solent, 50 feet. The surface of the ground is, of course, much cut up by the numerous streams coming in from the north; but the general fall of the gravel from west to east is perfectly in accordance with its having been deposited in the valley of an ancient river running in this direction, the whole of the southern side of which has since been carried away by the sea. Whether the old river had become tidal so far west as Hurst Castle, when first it was intercepted by the sea to the south, does not appear to me to be a matter of importance, inasmuch as no doubt a valley was already formed, along the course of which the encroachments of the sea would be more rapid than where the cliffs were higher, and more solid matter had to be removed. That the valley, in which is now Southampton Water, was also originally, for the most part, scooped out by the rivers coming from the north, which in remote times flowed into the old River Solent, is, I think, beyond all reasonable doubt. The increased volume of the ancient river, after receiving so important an affluent, is evinced by the widening of the channel, from Calshot Castle eastward by Spithead, to a full third more than it is to the west, along what is now the Solent Sea.
As to the character of the gravels at Bournemouth, it is, as already observed, hard to distinguish those presumably of fluviatile origin from the older and probably marine beds. In the railway-cutting between Bournemouth and Christchurch, I thought, however, that in places I could trace the superposition of the one upon the other. The more recent deposits contain water-worn fragments of quartz, granite, and porphyry, as was noticed long ago by Mr. Godwin-Austen,[2784]who, from this circumstance, saw reason for connecting them with the gravels capping the tabular hills of Devon and Dorset to the west.
It is, of course, evident that at the period when the river ran at this high level, past the spot where now is Bournemouth, all the land to the immediate west must have been far higher than it is at present, and that Poole Harbour could not have existed. In attempting to reconstruct the map of a country, the shores of which have been much wasted by the sea, in order to show what{695}must have been at some remote period the old coast-line, the task is rendered difficult and within certain limits impossible by the absence of any evidence as to the elevation above the sea of the land removed, and as to the channels along which the sea could work. In this case, however, there is a strong presumption as to the unbroken continuity of the chalk-range, and of its elevation having been much the same throughout, as it now is at both ends of the breach. The general character of the beds above the Chalk, so far as their power of resistance to water-action goes, seems also much the same at either extremity; though perhaps the beds at the Isle of Wight end of the breach are somewhat the harder. Assuming nearly equal conditions, and looking at the form of the present coast-line, which is indented by two distinct broad bays, it seems probable that the old course of the river may have been intercepted by the sea at two several points, the one nearer Poole and the other nearer Lymington. Directly this closer communication with the sea was formed for the Dorsetshire rivers, they would, of course, owing to the more rapid fall, excavate their valleys with greater speed at their mouth, and directly they became tidal, the sea would make rapid inroads on the soft sand and clay exposed to its action. So effective is this action, that at Hordwell Cliff the waste of the shore is said to be now going on at the rate of about a yard per annum,[2785]or upwards of half a mile every thousand years, though perhaps this is somewhat exaggerated.
In discussing this question, I have purposely avoided complicating the subject with the effects of any general lowering of the surface of the ground by erosion either chemical or mechanical; or of upheavals and depressions of the land during the period of the formation of the valleys, though no doubt this also has taken place, especially along the southern coast of Britain. I must, however, mention the existence of a submerged forest, occasionally visible at low water, at the foot of the cliffs at Bournemouth, which seems to show that there as elsewhere a depression of a former land surface has taken place. The late Mr. Albert Way, F. S. A., who had the opportunity of examining some of the stumps of trees exposed at rare intervals at low water, informed me that they appeared to be those of the true Scotch fir; and also that local tradition speaks of an impassable morass having, so late as the commencement of the present century,{696}intervened between the line of cliffs and the sea. On the occasion of one of my visits to Bournemouth, some of these stumps were fortunately visible, and were pointed out to me by Mr. Way at a spot but a few yards to the west of the pier, and between high and low water-mark. They appear to be of no very remote antiquity, geologically speaking, and to be connected rather with the present valley of the Bourne than with the valley of the old river Solent, as the trees, some of which were fully a hundred years old, grew on the surface of a thick bed of hard peat. Under any circumstances, however, the presence of such remains at the foot of the cliff does not tend to diminish our estimate of the antiquity of the freshwater beds containing the works of man, which we find occupying their summit.
In passing the deposits containing flint implements in different parts of this country under review, enough has, I think, now been said to show that in position, in character, and in the nature of their organic contents, they are perfectly in accordance with what might have been expected from river-action under certain circumstances. The case might indeed have been made much stronger had deposits in other places, in all respects similar, except that the presence of flint implements has not as yet been observed in them, been brought into account; and it must not be forgotten that this might, with perfect propriety, have been done, as there can be no possible doubt that a certain series of gravels, sands, and clays, containing organic remains and flint implements in extremely variable quantity, all belong to one geological period, and owe their existence to similar causes.
But though on no other hypothesis than that of river-action can the phenomena be accounted for, yet, as has already been seen, it is necessary, in order that river-action should have produced such effects, that the streams, during some portion of the year at all events, should have been more torrential in character than they are at the present day. If, however, we see satisfactory grounds for attributing these beds containing land and freshwater shells and remains of terrestrial animals, to rivers formerly flowing at much higher levels than at present, which have since excavated their valleys—and it seems impossible to do otherwise—then we must also accept as a fact that the climatal conditions were such as would enable the rivers to perform the work. It is, as Sir Joseph Prestwich[2786]has shown, quite out of the question{697}to suppose that with the valleys excavated to the present depth, any meteorological causes could fill them to their summits; or even if they could and did, that they would leave such deposits as we find at high elevations on their slopes, or even on detached eminences. It will, however, be well to examine briefly any corroborative evidence that may be forthcoming, as to the probability either of a severer climate involving a greater accumulation of winter snows, or of a greater rainfall, or of both. The one, indeed, seems hardly probable without the other, as a cold land surface “presented to vapour-laden sea-winds, as in the mountainous districts of the north-west of Spain, in our own lake districts, and in Scandinavia,”[2787]involves of necessity a heavy rainfall.
With regard to climate, we may take into account that which prevailed at a somewhat earlier date; for there appears no doubt that the flint implement-bearing gravels are all of later date than the Chalky Boulder Clay of the Eastern Counties, a deposit which belongs to the so-called Glacial Period, during a portion of which a great part of England and Scotland was submerged beneath the sea, and became coated with masses of Boulder Clay and other deposits, derived for the most part from the moraines of glaciers, sometimes at no great distance, and possibly in the main transported and dropped in their present positions by means of icebergs and coast ice. That they are of later date is proved by more than one of the implement-bearing beds reposing in valleys either in, or cut through, this Chalky Boulder Clay; and at Hoxne the interval between the Glacial deposits and the Palæolithic beds is marked by two sets of lacustrine strata, the lower and earlier with a flora characteristic of a mild climate, and the upper by one which points to the recurrence of Arctic conditions. Prof. Boyd Dawkins[2788]has suggested the probability of the higher ground of North Wales and the northern part of England having been still enveloped in an ice-mantle at the time that the mammoth, reindeer, and other post-glacial mammals were living in the lower and less inclement districts. But this view is to some extent founded on negative evidence, and on the assumption that palæolithic implements do not exist in this northern area. I have already commented[2789]on the possibility of implements being eventually found in it.
The crumpling and contortion of some of the beds of{698}River-drift, especially at high levels, has been regarded by Sir Joseph Prestwich[2790]as possibly resulting from the lateral pressure produced by packing and jamming together of blocks of ice, such as may now be witnessed in rivers like the Danube and the Rhine. The “trail and warp” of Mr. Trimmer, those superficial deposits so common over a large portion of this country, which, indeed, constitute so large a portion of the arable soil, seem also, as the Rev. Osmond Fisher[2791]has pointed out, to be significant of a severer climate than at present prevails. The “Palæolithic floors,” both near London and at Caddington, are buried under a considerable thickness of this “trail.” There is moreover a high probability that, at the time of the deposit of the gravels, Britain was still united to the continent; so that, apart from other causes, there was a tendency for the climate to partake more of a continental character than at present, and to induce greater cold in winter and greater heat in summer.
That the existence of enormous glaciers is as indicative of the action of heat, in order to convert the water of the ocean into vapour, as of cold to condense it, has been insisted on by Professor Tyndall,[2792]and even more strongly by Professor Frankland. If at the time of the rivers flowing at the high level, Britain was still connected with the continent, it is by no means impossible that the temperature of the seas on either side of the connecting isthmus may have been different. That connected more immediately with the Southern Ocean would have been the warmer of the two, from which a copious supply of vapour would be carried by the southerly winds, and be condensed as rain in its passage northward.
Mr. Alfred Tylor, F.G.S.,[2793]in his profusely illustrated papers on the Amiens gravel, and on Quaternary gravels, contends for the existence of a “Pluvial period” subsequent to the Glacial, in which the rainfall was far greater than at present, and such a view has much to commend it for acceptance. But when he proceeds to assert that the surface of the Chalk in the valley of the Somme, and in all other valleys of the same character, had assumed its present form prior to the deposition of any of the gravel or loess now to be seen there, and to argue that the whole of the gravels at all levels on the slopes are of one age, and due{699}to floods extending to a height of at least 80 feet above the level of the rivers, we may well hesitate before we give in our adhesion to such views. In the first place, it is, to say the least of it, unphilosophical to rely too much on a single example, such as that of the valley of the Somme; and to account for its phenomena by causes which are evidently incapable of producing the effects observable in other localities, as, for instance, at Southampton, close to the sea, and 160 feet above its level. But what shall we say to floods raising the levels of rivers upwards of 80 feet, yet having no erosive power, and the waters of which, regardless of the laws of gravity, tranquilly deposited their solid contents evenly over the slopes, or often in the greatest thickness on their higher part, and in some cases on almost isolated hills, instead of principally on the bottom of the river-valley? Whence all the materials for the gravels are to be derived, how they are to be reduced to a subangular condition by water-wear, especially in the case of the flint implements occurring in the gravels, are points on which further information will have to be supplied, before any such views can be seriously entertained.
I have up to this point almost left out of view any distinctive differences between the deposits at a high level and those at a low level in the river-valleys. That such, however, exist has been pointed out by Sir Joseph Prestwich;[2794]and judging from the northern range of the group of shells found in the high-level beds, the absence of southern species, the character of the mammalian and vegetable remains, the transport of large blocks such as could only be effected by ice and the other physical features of the case, he is inclined to assign a winter temperature to the period of their deposit from 19° to 29° Fahr. below that which now obtains in these regions. From a consideration of the features of the low-level deposits he considers that at the time of their deposit, the climate was rather less severe, by about 5°. The presence of the mammoth and woolly-haired rhinoceros, animals specially adapted for cold climates; of the musk-ox, the reindeer, the lemming, and marmot, corroborates the same view; while the hippopotamus, which seems characteristic of the low-level deposits, is suggestive of a somewhat warmer climate. Like the mammoth and rhinoceros, its structure may, however, have been somewhat modified, so as to enable it to occupy colder regions than at present, or it may have been merely a summer visitor ranging northwards before the{700}separation of Britain from the continent. Under any circumstances its presence seems to indicate that the volume of the rivers was probably in excess of what it is at the present time. But whatever may have been the degree of winter cold, or the amount of the snow and rainfall, the one was not so extreme as to prevent there being an abundance of animal life, nor the other so great as to interfere with the growth of a sufficient supply of vegetable food on which it might subsist.
It has, indeed, been supposed by some that the remains of the early mammals occurring in the gravels are derived from older beds, and that their presence in association with flint implements no more proves the contemporaneity of the men who made those implements with the old Quaternary fauna, than their association with Chalk fossils proves that mankind were originally inhabitants of the bed of the Cretaceous ocean. Did the gravels only occur at such levels as are within reach of existing streams, there might be some reason in such a view, which is, moreover, in certain cases and within certain limits, probably correct. For we have seen how in the course of the excavation of a valley, the beds deposited at one time are liable to be disturbed at another, and re-deposited in a fresh place; which could hardly happen without an admixture of fresh materials, some probably of a more recent date. In the process of transport, however, not only the implements but the still softer bones are liable to wear and abrasion of the angles, and it is impossible to conceive that, assuming the Quaternary fauna to have disappeared from this region before the valleys were excavated, and the implement-bearing beds deposited, their bones could still exist in such numbers, and so often in an unrolled condition in the low-level beds.
Had this older fauna disappeared, it is evident that man could not have subsisted here alone, unaccompanied by other animals to furnish him with food; and if these animals belonged to the later or “prehistoric” fauna, where, as Sir John Lubbock pertinently asks, are their bones? If, however, we acknowledge that the pleistocene mammals still occupied this country at the time of the low-level beds being formed, and if we find their remains also in those at a high level, and at all intermediate heights, it is evident that they must have persisted here during the whole period of the excavation of the valleys; while, if we find also flint implements in an unrolled and unworn condition at all heights, it is evident that those who made them must also have been{701}co-occupants of the region during the same period. If, indeed, as appears to be in some valleys the case, the unworn implements occur only in the high-level deposits, while in the lower they are either absent or in a much worn condition, the inference is, that in those particular valleys the occupation by man, though for some time contemporaneous with that of the mammoth and his congeners, ceased before the extinction or emigration of the old fauna. In some cases, however, as at Fisherton,[2795]the worked flints have been found below the remains of mammoth; while in the beds at Menchecourt, near Abbeville,[2796]in which the implements occur, were found the bones of a hind leg of rhinoceros still in their natural position, so that they must have retained their ligaments when deposited, and could not since have been disturbed. With regard to the amelioration of climatal conditions which led to the cessation of the excavation of the valleys, it may not impossibly have been connected with the insulation of the country, when the isthmus connecting it with the continent was cut through by the sea. But this is hardly the place for such speculations. If, however, we may regard the estuarine deposits at Selsey, in which almost entire skeletons of mammoth occur, as belonging to the period when the deposit of the low-level gravels was ceasing, it would appear from the associated molluscan forms, as interpreted by Mr. Godwin-Austen, that the temperature of the waters of the English Channel was at that time such as may now be met with twelve degrees farther south.
If there was a difference in the climatal conditions of the high and low-level deposits, it might have produced some effect on the method of living, and on the implements of the men of the two periods. At one time I thought it probable that a marked distinction might eventually be drawn between the high-and low-level implements, but so far as Britain is concerned, this can hardly be done. Still thefaciesof a collection from two different spots is rarely quite the same, and I think there is generally a preponderance of the ruder pointed implements in the high-level gravels, and of the flat ovate sharp-rimmed implements in the low-level. In the valley of the Somme, the broad polygonal flakes are certainly most abundant in the lower beds, as at Montiers, near Amiens.
I would, however, deprecate the introduction of such terms as{702}“Eolithic” and “Mesolithic” in order to distinguish two phases in the Stone Period as being both unfounded and misleading. We know not where or when the dawn of human civilization arose, but it was probably long before the date of our earliest River-Gravels and in some part of the world more favoured by climate than Britain. Why then should we speak of British implements as Eolithic? And how can we apply the term Mesolithic to a period intervening between the Palæolithic and Neolithic Ages, when we know neither when the one ended nor when the other began?
Enough has now been said with regard to the manner in which these beds of River-drift were probably deposited; and the irresistible conclusion is, that, owing to the wasting agency of rain, frost, and rivers, there must have been a vast change in the superficial features of the country, since the time when those who fashioned the flint implements found in the high-level gravels were joint occupants of the land with the mammoth and rhinoceros and the other departed members of the Quaternary fauna. A similar change in the surface of the country has also taken place in the neighbourhood of the caves in which the remains of this same fauna occur, associated also with similar relics of human workmanship.
What length of time it must have taken for such changes to be effected, is a question we must now approach; but before doing so it will be well to say a few more words, in addition to what has already been said, on the almost entire absence of human bones in the beds containing those of the associated mammalia.
In the first place, it is well to repeat that whatever may be the case in the brick-earth, or loess, there have not, as has been pointed out by Sir John Lubbock,[2797]been found in the gravel up to the present time any remains of animals so small as man, who, as the same author observes, must of necessity have been few in number in comparison with the animals by the chase of which he must have subsisted. Another cause appears also to have been at work; for however barbarous we may suppose the human race to have been at that remote period, we can hardly believe them to have been so destitute of all natural affection as to deny some rites of sepulture to friends or relatives removed by death. There would, therefore, in all probability, be but few or no human bones exposed on the surface in such a manner as to be carried off by the flooded streams, and imbedded in their gravels; while, in case of any human beings perishing by drowning, their bodies, as I have{703}already shown, would probably either be carried to sea, or left in such a position as to allow of their recovery, at all events before they became disarticulated.
This is, however, a matter of but small importance, as there will be but little difficulty in conceding that an implement fashioned by human agency—and on this point there can be no question, unless we are to assume in ancient times the existence of some other now extinct race of intelligent beings—is as good an evidence of the existence of man, as would be any or all of his bones. Moreover, human bones are reported to have been discovered in these Quaternary beds, both in this country and in France. In England, I have already mentioned a human skull found near Bury St. Edmunds by Mr. Trigg, and the more doubtful skeleton found near Northfleet. I will not, however, insist upon either discovery being beyond all cavil.
Nor will I do more than allude to the too celebrated Moulin Quignon jaw, over which I have already pronounced aRequiescat in pace,[2798]but the discovery of portions of the human skeleton by M. Bertrand, and M. Reboux, in the valley of the Seine, at Clichy[2799]and elsewhere near Paris, in the same beds in which implements of true Palæolithic types have been found, seems better substantiated.
Whether thePithecanthropus erectusof Dr. Dubois was human or simian, and what is the date of the beds in which his remains were found, and whether there is evidence of the existence of Miocene or Pliocene Man[2800]in Burma, Portugal, France, Italy, or California, are questions which want of space compels me to leave on one side. I have, however, more than once elsewhere expressed my opinion on the subject of Tertiary Man.[2801]
I need hardly again repeat that according to my view it is not in Britain, but in some part of the world more favoured by climate that the cradle of the human race is to be sought. And yet the antiquity of Man in Britain seems to extend far beyond any of our ordinary methods of computation. In attempting to estimate it, however vaguely, I must at the outset observe that with our present amount of knowledge, it is hopeless to expect that it can{704}be determined with anything approaching to precision. Not only have we no trustworthy measure of the rate of excavation of the valleys, which might give us an approximate date for the higher deposits in them, but we are at a loss to know at what epoch their excavation in the lower part of their course ceased, and what may be termed the modern alluvial deposits, which to some extent have partially refilled the old channels, began to accumulate.
That the general configuration of the surface of the country, in Neolithic times, when the ordinary forms of polished stone implements were in use, was much the same as it is at present, is proved by the fact of such implements being frequently found in recent superficial deposits. Were we, in defiance of probability, to assume that the use of these polished implements did not date farther back than two thousand years from the period when we are first made acquainted with this country by history, this would give an additional four thousand years beyond the period necessary for the excavation of the valleys for the date of the older River-drift implements. Such a period as two thousand years is in all probability almost ridiculously small to assign for the duration of the Neolithic and Bronze Periods; but however this may be, there appears, in this country at all events, to be a complete gap[2802]between the River-drift and Surface Stone Periods, so far as any intermediate forms of implements are concerned; and here at least the race of men who fabricated the latest of the palæolithic implements may have, and in all probability had, disappeared at an epoch remote from that when the country was again occupied by those who not only chipped out but polished their flint tools, and who were, moreover, associated with a mammalian fauna far nearer resembling that of the present day than that of Quaternary times.
So different, indeed, are the two groups of animals that, as has already been observed, Prof. Boyd Dawkins[2803]has shown that out of forty-eight well-ascertained species living in the Post-glacial or River-drift Period, only thirty-one were able to live on into the Prehistoric or Surface Stone Period. Such a change as this in the fauna of a country can hardly have been the work of a few years, or even of a few centuries; and yet we must intercalate a period of time sufficient for its accomplishment between the remotest date{705}to which we can carry back the Neolithic Period, and the close of the Palæolithic Period as indicated by the low-level gravels. The antiquity, then, that must be assigned to the implements in the highest beds of River-drift may be represented (1) by the period requisite for the excavation of the valleys to their present depth; plus (2), the period necessary for the dying out and immigration of a large part of the Quaternary or Post-Glacial fauna and the coming in of the Prehistoric; plus (3), the Polished Stone Period; plus (4), the Bronze, Iron, and Historic Periods, which three latter in this country occupy a space of probably not less than three thousand years.
A single equation, involving so many unknown quantities, is, as already observed, not susceptible of solution; but various attempts have been made to arrive at some approximate idea of the amount of time it represents. One method has been that of assigning a date for the Glacial Period, deduced from astronomical causes, mainly in connection with the eccentricity of the earth’s orbit, as pointed out by M. Adhémar and Mr. Croll. From data thus obtained, Sir Charles Lyell[2804]inclines to place it at a period of extreme cold about 800,000 years ago, though Sir John Lubbock[2805]would rather accept an epoch of somewhat less severity about 200,000 years removed from our time.
Another and more direct method suggested by Sir Archibald Geikie,[2806]following in Mr. A. Tylor’s track, is that of estimating the time required for the excavation of the valleys by the amount of solid matter carried down in suspension by various rivers at the present day. He estimates that this amount, if spread over the whole area drained by the rivers, represents, on an average, an annual loss of about1⁄6000of a foot; but inasmuch as the erosion of the slopes and watercourses is very much greater than that of the more level grounds, the excavation of the valleys must proceed at a more rapid rate, which he assumes to be about1⁄1200part of a foot per annum, or one foot in 1,200 years. Such a calculation is, of course, open to various objections, as we may readily conceive the bottom and slopes of a valley to have been so far washed that, under ordinary circumstances, they afford little or no fine earthy matter to be taken up by the rain falling on their surface; and in such a case, the rivers, if turbid, would derive their turbidity from the water delivered from the higher and comparatively{706}unwashed table lands. Or again, the soil may, like the Chalk under ordinary circumstances, be so absorbent that but little of the rainfall flows off from its surface. The calculation has already been made, that a rainfall of 54 inches annually, supposing the whole of it flowed off the land into the sea in a turbid state, containing, like the Mississippi,1⁄1500part of its weight of solid matter, would lower the surface a foot in 450 years; but as has already been observed, we cannot conceive it possible that with such soils as we have here to do with, the constant turbidity should have been anything like so great. And, in fact, the whole system of calculation is one which may be regarded rather as proving the necessity of valleys being in course of time formed by subaërial action, than as giving any definite guide by which to calculate the period requisite for their formation. There can, indeed, be no doubt that the denuding power of the falling rain is greater on the slopes than on the level surfaces; but it seems impossible to assign any proportions to the effects on land lying at different inclinations, of different characters, and under different circumstances as to any vegetable covering. Were the action uniform over the whole surface exposed, of course no alteration beyond a general lowering of the land-surface would result from this cause, and the valleys would remain of precisely the same depth with regard to the adjacent land as they did at remote epochs. Looking at the quantity of brick-earth still left on the slopes of many of our valleys, I am inclined to think that the lowering of the surface has been more general than has been supposed by Sir Archibald Geikie. The presence of these soft and easily denuded beds is also an argument against the excavation of the valleys having progressed in a uniform manner, by heavy rains falling during the period of the year when such beds were soft and unfrozen; and seems rather significant of the excavation of the valley by floods principally occurring at a time when the upper part of the soil was in a frozen condition.
Certainly the whole character of the deposits is more in accordance with their resulting from the occasional flooding of the streams than from any other cause. If this be so, who shall tell at what intervals such floods occurred, and what was the average effect of each in deepening the valleys? That they were of comparatively rare occurrence, and not so frequent that they were foreseen by the men of those days, seems deducible from the number of their implements found in the gravels. For there is much probability that these must have been washed in from{707}settlements on the banks of the rivers, which, notwithstanding previous catastrophes of the same kind, were constantly placed within reach of the stream when flooded.
Sir Joseph Prestwich[2807]has suggested as a possible gauge of the antiquity of the deposits, the natural funnels eaten into the chalk by the action of water charged with carbonic acid, and has cited one at Drucat, near Abbeville, which has been formed since the deposit of the gravel containing flint implements, and is upwards of 20 feet in diameter at top, and probably 100 feet in depth; but here also it seems impossible to introduce a factor by which the time represented can be ascertained. There are, however, features in connection with this case which can only be reconciled with the former high level of the bottom of the adjacent valley, and with its gradual excavation. It will be remembered that similar pipes of erosion, leading in some cases to caverns above them, occur in the Drift-beds of the valley of the Little Ouse.
There is yet another means at our command for forming, at all events, an approximate idea of the time that has elapsed since the deposit of the beds containing the remains of the old Quaternary fauna, inasmuch as at the time of their introduction into this country, if not for a lengthened period afterwards, Britain had apparently not become an island, but was still connected by an isthmus of greater or less width with the Continent. To estimate the time, however, that would be required for cutting through this isthmus and widening the Channel to its present dimensions, is a work from which the mind almost recoils. Even the wearing away of that tract of land to the south of the present Hampshire coast, which must almost of necessity have existed at the time when the Bournemouth flint implement-bearing gravels were deposited, taking the present rapid inroad of the sea on the unusually soft cliffs at Hordwell as a guide, would seem to involve a period of not less than 10,000 years; but inasmuch as the cliffs during a considerable portion of the time must have been of chalk instead of sand and clay, and as a chalk cliff 500 feet high, instead of being worn away at the rate of a yard each year, is said only to recede at the rate of an inch in a century,[2808]the actual period necessary for the removal of this tract must probably have been many{708}times 10,000 years, and can with certainty be regarded as having been immensely in excess of such a lapse of time.
On the whole, it would seem that for the present, at least, we must judge of the antiquity of these deposits rather from the general effect produced upon our minds by the vastness of the changes which have taken place, both in the external configuration of the country and its extent seaward, since the time of their formation, than by any actual admeasurement of years or of centuries. To realize the full meaning of these changes, almost transcends the powers of the imagination. Who, for instance, standing on the edge of the lofty cliff at Bournemouth, and gazing over the wide expanse of waters between the present shore and a line connecting the Needles on the one hand, and the Ballard Down Foreland on the other, can fully comprehend how immensely remote was the epoch, when what is now that vast bay was high and dry land, and a long range of chalk downs, 600 feet above the sea, bounded the horizon on the south? And yet this must have been the sight that met the eyes of those primeval men who frequented the banks of that ancient river which buried their handiworks in gravels that now cap the cliffs, and of the course of which so strange but indubitable a memorial subsists in what has now become the Solent Sea.
Or again, taking our stand at Ealing, or Acton, or Highbury, and looking over a broad valley fully four miles in width, with the river flowing through it at a depth of 100 feet below its former bed, in which, beneath our feet, are relics of human art deposited at the same time as the gravels; which of us can picture to himself the lapse of time represented by the excavation of a valley on such a scale, by a river larger, it may be, in volume than the Thames, but still draining only the same tract of country? But when, to this long period we mentally add that during which the old fauna, with the mammoth and rhinoceros, and other to us strange and unaccustomed forms, was becoming extinct, so far as Britain was concerned; and also that other, we know not how lengthened period, when our barbarous predecessors sometimes polished their stone implements, but were still unacquainted with metallic tools; and then beyond this, add the many centuries when bronze was in use for cutting purposes; and after all this, further remember that the ancient and mighty{709}city now extending across the valley does not, with all its historical associations, carry us back to the times even of the bronze-using people, the mind is almost lost in amazement at the vista displayed.
So fully must this be felt, that we are half inclined to sympathize with those who, from sheer inability to carry their vision so far back into the dim past, and from unconsciousness of the cogency of other and distinct evidence as to the remoteness of the origin of the human race, are unwilling to believe in so vast an antiquity for man as must of necessity be conceded by those, who however feebly they may make their thoughts known to others, have fully and fairly weighed the facts which modern discoveries have unrolled before their eyes.
FINIS.
PLATE I.
1. Simple ridged flake.Porte Marcadé, Abbeville.
2. Sharp-pointed flake, with several facets on its convex side.Montiers, near Amiens.
3. Chisel-pointed flake.Ibid.
4. Large polygonal flake.Ibid.
5. Round-pointed, tongue-shaped, sub-triangular implement.Biddenham, near Bedford.
6. Acutely pointed, kite-shaped ditto.St. Acheul, near Amiens.
7. Sub-triangular ditto, with truncated butt.Ibid.
8. Ditto, with incurved sides, and butt formed of the natural surface of the flint.Ibid.
9. Ditto, made from a round-ended nodule of flint.Ibid.
10. Thick-backed, single-edged implement of wedge-shaped section.Ibid.
PLATE II.
11. Ovate tongue-shaped implement.St. Acheul, near Amiens.
12. Ovate-lanceolate ditto, with rough butt.Ibid.
13. Ditto, with truncated butt. (Brick-earth),St. Acheul, Amiens.
14. Rough, wedge-shaped implement.St. Acheul, Amiens.
15. Round-pointed implement with untrimmed butt.Ibid.
16. Ditto, with naturally rounded butt and side.Ibid.
17. Thin, ovate, tongue-shaped implement.Champ de Mars, Abbeville.
18. Ovate implement of intermediate form between the tongue-shaped and sharp-rimmed.St. Acheul, Amiens.
19. Ovate, thin, sharp-rimmed implement.Menchecourt, Abbeville.
20. Irregularly ovate ditto.Moulin Quignon, Abbeville.