ments and fossil bones, and bids us reflect that they at least could not have been conveyed to where we see them by any known force of water short of that which it derives from the vehement internal heavings of the earth's crust. If the possibility is suggested of their having been transferred hither by the floating power of ice, he directs our regard triumphantly to the bones of Rhinoceros, Elephant, and Hippopotamus, with which the boulders are associated, as testifying to probably a warmer, certainly not a colder, climate than that now prevailing in France, where no such process takes place. He further asks our attention to the obvious marks presented by these blocks, of their having been roughly bouldered in contact with materials capable of extensively rubbing down all their corners, edges, and original surfaces; and, ever ready for a skirmish in support of his ideas, he throws down the gage of battle by demanding defiantly of the Quietist, by what processes of slow deposition, erosion, and elevation, he proposes to explain not only these phenomena, but the fact that the deposit is spread broadcast over all the valley of the Somme, from beneath the peaty meadows which bound the river, up the gently ascending slopes of this wide shallow trench in the land, to the summits of the plateaus which determine the existing drainage, distributed diffusedly, too, and not in terraces, such as might denote oscillations in the relative levels of land and sea.

When questioned as to the length of time occupied in its formation by the next stratum-the bed of white and brown sand, from 7 to 10 feet thick, lying immediately on the gravel the advocate of gradual changes will respond, that assuredly here, at least, we witness the indications of a quiet and greatly protracted period. He will exclaim exultingly, Behold this very regular lamination, this firmness and evenness, and, for a portion of the bed, this water-worn smoothness of the granules; and take note especially of the delicacy of these numerous small, fragile, fresh-water shells, identical in species with some of the molluscs now inhabiting the region. What stronger proof could be required

that an ancient river or long lake filled the broad valley of the Somme, if not after the entombing of the fossil bones and the hatchets, at least late in the period of the animals and men who owned them; and what more convincing monument could such a sheet of fresh water have left behind it of its having existed during an immense lapse of ages?

He of the Paroxysmist school, contemplating the same phenomena, and some others, perhaps naturally overlooked by his friendly opponent, the advocate of slow mutations, is willing to concede the fresh water, and consequently some important changes in the physical geography of the district since those days, but he resolutely dissents from the inference that the sand must have required a very long time to form, and insists on calling our attention to three facts-first, that a portion of the sand is very sharp and angular, indicating a rather transient movement; secondly, that its lamination is by no means either level or uniform, but in many localities is disturbed, undulating with the very undulating floor of gravel; and, thirdly, that the trenches, hollows, and ridges in this floor or upper surface of the gravel, of themselves imply that the current which first passed across it, that of course which overspread it with the sand, was something far swifter than a quiet inflow of silting water-was, in truth, endowed with that far from trivial velocity which confers the power of eroding and ploughing up already settled or impacted subangular matter, and of carrying part of it bodily away. Perhaps he will add that the thickness of the sand is no true measure of the time it has consumed in forming, inasmuch as under certain easily indicated favourable conditions, of retardation of a current bearing floating particles, as great a depth of sediment will accumulate in a few years, as would, under a normal state of things, consume many centuries in collecting. We, self-constituted umpires in this discussion, interpose our conviction that neither of these earnest interpreters of nature is competent, in the present state of science, to pronounce with any positiveness whether the formative pro

cess was slow or rapid; for how slowly or how rapidly a given foot or fathom of silted sand has taken to stratify itself, no geologist of either school will venture soberly to calculate, especially when he reflects that neither school has hitherto succeeded in attaining that familiarity with all the modes of operation of that most marvellous agent, water, without acquiring which, it is in vain to hope for a quantitative measure of its rates of action, under apparently the most simple conditions."

Maintaining our station at the gravel-pits, with our two "representative men," our Quietist and Paroxysmist interpreters of the geology, we tire at the prospect of receiving somewhat similar explanations to those just heard, if we venture to ask what time it took to form the two remaining beds in the bank-the narrow wildly-tossed layer of gravel, and the faintly - laminated brown sandy clay or brick-earth, which caps the series, nourishes the grass, and shelters the Roman graves. We therefore terminate our interrogations by demanding of the champion of each school his own explanation of the successive physical changes witnessed by this region of the Somme since the period of the gigantic mammals, that we may, by contrasting the two theoretical histories, the better appreciate what Geology has at present to say in relation to our leading inquiry-the probable antiquity of the primeval race of Men who left behind them the flint-implements of the Diluvium.

The Quietist, or student of nature's more tranquil moods and changes, will probably offer something like the following historic sketch. Starting with the formation of the gravel, which contains the mammalian bones and flint-implements, he will conceive it to have been spread over the surface of the chalk by a broad river subject to inundations, filling the valley of the Somme, and submerging the carcasses, or at least the bones, of the animals pasturing near its borders. To explain the wide distribution laterally of the ossiferous gravel, and its altitude above the present bed of the valley, it will be necessary to suppose that this river,

or mass of fresh water, commenced its formative functions at a higher level, or one nearer that of the plateau through which it now flows

running on or over the upland, and not below or within it, as it now does-and that the drainage has gradually excavated the valleys of the Somme and its tributaries to their present lower levels, collecting and strewing on their shifting beds and banks the flint-gravel, with its embedded bones and human relics. By assuming that this sinking of the river-bed was continuous, and attended probably by a continuous rising of the level of the land above the sea, and was not accompanied by any long pauses, or interrupted by counter-movements of subsidence, we can account for the total absence of traces of either sea - margins or river-terraces, and for the uniform manner in which the gravel clothes the eroded surface of the chalk, and conforms to all its slopes. The cutting out or trenching of the valleys is thus attributed to a fluviatile erosion, demanding an immense lapse of time for its accomplishment, and not to an invasion or successive invasions of the sea, carving and modelling the land for the reception and conveyance of the atmospheric waters. The suggestion of an antiquity for the human family so remote as is here implied, in the length of ages required by the gentle rivers and small streams of northeastern France to erode its whole plain to the depths at which they now flow, acquires, it must be confessed, a fascinating grandeur, when, by similitude of feature and geology, we extend the hypothesis to the whole north-west frontier of the continent, and assume, that from the estuary of the Seine to the eastern shores of the Baltic, every external feature of valley, dale, and ravine-in short, the entire intaglio of the surface-has been moulded by running waters, since the advent of the human race.

Perhaps the geologist of the school disposed to recognise only the more gradual changes in the configuration of the surface, conscious of the grave difficulties which beset the present application of this hypo

thesis, will adopt a different explanation, and set out with the conception that the great valleys of the land were already scooped before the strewing of the Diluvium or ossiferous gravel. His most natural assumption will then be, that the gravel was deposited in the bed and on the shores of a tidal estuary, frequented by the makers of the flint hatchets and by the extinct quadrupeds, and that the stratum was diffused wider and higher by a progressive sinking of the land, submerging successively fresh tracts, till all the district now capped by this particular Diluvium was overspread. This supposition involves a much less protracted period than the preceding, not more time, indeed, than, at the rate of elevation or subsidence of the earth's crust at present in progress on sundry coasts, would depress the district of the Somme perhaps one hundred feet. Certain indispensable evidence, of like nature in both cases, is wanting to lend countenance to either of these hypotheses. There are no independent proofs, in the form of fluviatile shells, of the long residence of the rivers within their existing valleys at materially higher levels than those they now occupy, to confirm the former view; nor any similar monuments of the long residence of the sea, or of estuary waters, in the shape of marine organic remains in the bed and on the lower slopes of the valley, to sustain the latter. Till such are found, both hypotheses may be received as suggestive speculations, but cannot be accepted as steps towards a sound theory of the origin of the flint-gravel of the Somme.

Ascending to the beds which overlie this "sepulchral earth" of the mammoth and his associates, our friend of the tranquil school will account for them, by appealing to processes very similar to those already invoked. He will show us, that the bed many feet thick of white and brown sand, with the fragile fresh water shells, testifies unequivocally to some ancient river long and quietly resident above the gravel. But these fresh-water sands cover the gravel almost as broadly and continuously as the gravel

covers the chalk, and, what is especially puzzling, occur at all altitudes upon the gently ascending sides of the valley, from its bed to the tablelands which bound it. Here another complex process of shifting river sedimentation, with slow depression or elevation of the land, must be resorted to, demanding a lapse of time commensurate with, or even exceeding, that previously required. Thus, proceeding through the thinner rudely eddied gravelbed which succeeds the river sand, and through the brick-earth, or ferruginous sandy clay with splinters of flint, which crowns the entire series, sustains the now existing life of the district, and entombs some of that which was of human mould almost two thousand years ago, he will, with like ingenuity, establish the probability of two other enormous epochs, making thus in all four vast revolutions of the geologic index on this immeasurable dial-plate, all between the embedding of the manipulated flints and extinct mammalians, and the sepulture of the Roman occupants of the country.

Let us now listen to the Paroxysmist, who desires to measure the earth's rates of progress, not only while she dallies with her tools, but when she puts forth her nearly resistless strength. By what agencies, and in what relative time, does he conceive these four superficial strata may have been produced?

Beginning, as before, with the gravel-bed at the base of the series, he will allege that this can have occupied no very long period in its formation; for, pointing to the sundry marks of diluvial or turbulent aqueous action which it betrays, he will remind us that the motion of the strewing current must have been rapid, and that time is ever in the inverse ratio of velocity. His notion of the order of events will probably be something like the following:-Assuming the pre-existing relief, or excavation rather, of the surface, to have approximated to that now prevailing, he will account for the gravel by supposing a sudden rocking movement of the land and the bottom of the sea of the nature of an earthquake, or a succession of them, to have launch

ed a portion of the temporarily uplifted waters upon the surface of the land, the inundation penetrating further inland, rising to higher altitudes, and possessing more sweeping and destructive power, along the broad, gently-ascending, trumpet-mouthed valleys like the Seine and Somme, than on the unindented plain. To this inundation, or more strictly to a series of such for these vehement disturbances of the earth's crust usually repeat their visits to the same district many times in an epoch of commotion-he will ascribe the ploughing up or washing up of the surface beds of the chalk, the sorting out, as it were, and breaking, rolling, and rudely strewing of its embedded flint-nodules, and the entombing of the huge wallowing animals enticed by their instinctive wants to inhabit the tracts especially vulnerable to inundation. Reflecting on the insufficiency of the evidence which would make man the contemporary of the extinct Mammoth, he will encounter no difficulty in explaining how Man's remains may have become buried at a long subsequent epoch in the same Diluvium or Drift which had already received the bones of the colossal Elephant and his associates; for he will remind us that a second disturbance of the crust, similar to that which had already entombed the quadrupeds, would, if occurring within historic time, find the physical conditions even more suitable for an entombing inundation than the first. The same valleys and low plains would invite an invasion of the sea, only they would this time be smoothed over with the ossiferous gravel; and this bed for the waters would be torn up, drifted, and deposited afresh with whatsoever man may have left upon its surface, far more readily than was the well-impacted chalk by the previous great inundation.

Ascending to the next bed-the silicious sand with fresh-water shellsthe Paroxysmist will account for this by requesting us to imagine a broad river pouring its steady current over the bed of the valley, its waters charged from time to time with more or less angular sand, washed out of the adjacent gravel then constituting

the rising grounds on both sides. To explain how the sand has come to cover the gravel beyond the immediate borders of the valley, following that stratum to the upper slopes and apparently even to the general tableland of the country, he will ask us to note the fact, that while it is horizontally and evenly laminated in the less elevated localities, it displays in those of a higher level, for instance at St Acheul, a lamination often much disturbed and oblique, and a very irregular lower and upper boundary; features, all of which plainly intimate that it may have been swept suddenly into these upper levels, by a paroxysmal movement of the earth's crust analogous to that which preceded it, and produced the ossiferous gravel beneath.

In confirmation of this view, the advocate of subterranean forces, as the primary agents in producing the superficial sediments, may point our attention to the conical pits or hollows in the surface of this bed of sand, already alluded to, and appeal to them in proof that a sheet of water in rapid and whirling motion must have swept over the land about the close of its deposition, the prelude, it would seem, of the precipitation of the upper gravel-bed on that which covers the sand, if not the very current itself which bore along the gravelly materials, and laid them where they now repose.

That this third stratum--the second gravel-was thus deposited by a swift and eddying current, is so distinctly indicated, not merely by the feature now pointed out, but by its irregular and oblique or diluvial lamination-if proper lamination it can indeed be said to possess-that the Paroxysmist is here confident that he beholds a record of only a very brief period of time.

Reaching the fourth and uppermost bed of all-the brown ferruginous sandy clay or brick-earth with splinters of dispersed flint-the geologist familiar with the signs of both gentle and violent watery action will recognise the most quiet, and therefore the most time-representing sediment of the entire series. But even in this material, the average thickness of which is between three and

five feet, he will draw our attention to the abundance and occasional size of these fragments of flint, and may demand how they could have been introduced by water in very sluggish motion. He will probably abandon some of his scepticism upon this point, however, if we request him to observe the almost total absence of distinct lamination in the clay and the general fineness of its texture; the absence of lamination or internal stratification being one of his surest criteria of a perpendicular deposition, it may be slowly or it may be rapidly, in water either permanently or transiently at rest; the slowness or rapidity of the precipitation, again, being indicated mainly by the fineness or coarseness of the materials. So, looking at this uppermost deposit of all, the minimum age of which is proved to equal at least one-third of the commonly imputed age of the human race, by the presence within it of Gallo-Roman graves, and other remains historically identifiable, he hesitates to acknowledge that even it can have occupied any prolonged series of ages in its production.

The physical conditions under which it has been formed, he will not venture to speculate about, until so important a stratum, the floor of the now living creation, the outer covering of the tomb which enwraps the bones and dust of all the organisms which once lived in the region and now live no more, shall have received a far more critical and widely extended study than it has yet enlisted.

Thus will the two translators of this last chapter in the Physical History of the Earth differ in their reading of each successive page: the one interpreting the record only by the gentler forces of existing nature, and inferring an enormous age for man, far transcending that deduced by the chronologists, while the other, adopting a quicker rate of formation, confesses his uncertainty as to whether these deposits originated within the accepted period of human history or not.

Having discussed the leading topics mentioned in my programme as fully as explicitness demands, I take leave of my reader with a brief

recapitulation of the conclusions I have arrived at.

1. To the question, Are the socalled flint-implements of human workmanship or the results of physical agencies? My reply is, They bear unmistakably the indications of having been shaped by the skill of man.

2. To the inquiry, Does the mere association in the same deposit of the flint-implements and the bones of extinct quadrupeds prove that the artificers of the flint-tools and the animals coexisted in time? I answer, That mere juxtaposition of itself is no evidence of contemporaneity, and that upon the testimony of the fossil bones the age of the human relics is not proven.

3. To the query, What is the antiquity of the Mammalian bones with which the flint-implements are associated? My answer is, That, apart from their mixture with the recently-discovered vestiges of an early race of men, these fossils exhibit no independent marks by which we can relate them to human time at all. The age of the Diluvium which embeds the remains of the extinct mammalian animals must now be viewed as doubly uncertaindoubtful from the uncertainty of its coincidence with the age of the flint-implements-and again doubtful, if even this coincidence were established, from the absence of any link of connection between those earliest traces of man and his historic ages.

Upon the special question involved in this general query, What time must it have required for the physical geography adapted to the Pachyderms of the antediluvian period to have altered into that now prevailing, suited to wholly different races? the geological world is divided between two schools of interpretation

the Tranquillists, who recognise chiefly Nature's gentler forces and slower mutations, and the Paroxysmists, who appeal to her violent subterranean energies and her more active surface-changes.

4. To the last interrogation, How far are we entitled to impute a high antiquity to these earliest physical records of mankind from the nature of the containing and overlying se