Part 36 (2/2)
[116] It is told of a former distinguished and witty member of the Geological Society that, having obtained possession of the rooms on a certain day, when there was to be a general meeting, he decorated its walls with a series of cartoons, in which the parts of the members were strangely reversed. In one cartoon Ichthyosauri and Plesiosauri were occupied with the skeleton of h.o.m.o sapiens; in another, a party of Crustaceans were occupied with a cranium suspiciously like the same species; while in a third, a party of Pterichthys were about to dine on a biped with a suspicious resemblance to a certain well-conditioned F.G.S. of the day.
[117] ”epoques de la Nature,” vol. xii., pp. 322-325. 18mo. Paris, 1778.
The antiquity of man is a question which has largely engaged the attention of geologists, and many ingenious arguments have been hazarded, tending to prove that the human race and the great extinct Mammalia were contemporaneous. The circ.u.mstances bearing on the question are usually ranged under three series of facts: 1. The Cave-deposits; 2.
Peat and sh.e.l.l mounds; 3. Lacustrine habitations, or Lake dwellings.
We have already briefly touched upon the Cave-deposits. In the Kirkdale Cave no remains or other traces of man's presence seem to have been discovered. But in Kent's Hole, an unequal deposit of loam and clay, along with broken bones much gnawed, and the teeth of both extinct and living Mammals, implements evidently fas.h.i.+oned by the human hand were found in the following order: in the upper part of the clay, artificially-shaped flints; on the clay rested a layer of stalagmite, in which streaks of burnt charcoal occurred, and charred bones of existing species of animals. Above the stalagmite a stone hatchet, or celt, made of syenite, of more finished appearance, was met with, with articles of bone, round pieces of blue slate and sandstone-grit, pieces of pottery, a number of sh.e.l.ls of the mussel, limpet, and oyster, and other remains, Celtic, British, and Roman, of very early date; the lower deposits are those with which we are here more particularly concerned. The Rev. J.
MacEnery, the gentleman who explored and described them, ascertained that the flint-instruments occupied a uniform situation intermediate between the stalagmite and the upper surface of the loam, forming a connecting link between both; and his opinion was that the epoch of the introduction of the knives must be dated antecedently to the formation of the stalagmite, from the era of the quiescent settlement of the mud.
From this view it would follow that the cave was visited posteriorly to the introduction and subsidence of the loam, and before the formation of the new super-stratum of stalagmite, by men who entered the cave and disturbed the original deposit. Although flints have been found in the loam underlying the regular crust of stalagmite, mingled confusedly with the bones, and unconnected with the evidence of the visits of man--such as the excavation of ovens or pits--Dr. Buckland refused his belief to the statement that the flint-implements were found beneath the stalagmite, and always contended that they were the work of men of a more recent period, who had broken up the sparry floor. The doctor supposed that the ancient Britons had scooped out ovens in the stalagmite, and that through them the knives got admission to the underlying loam, and that in this confused state the several materials were cemented together.
In 1858 Dr. Falconer heard of the newly-discovered cave at Brixham, on the opposite side of the bay to Torquay, and he took steps to prevent any doubts being entertained with regard to its contents. This cave was composed of several pa.s.sages, with four entrances, formerly blocked up with breccia and earthy matter; the main opening being ascertained by Mr. Bristow to be seventy-eight feet above the valley, and ninety-five feet above the sea, the cave itself being in some places eight feet wide. The contents of the cave were covered with a layer of stalagmite, from one to fifteen inches thick, on the top of which were found the horns of a Reindeer; under the stalagmite came reddish loam or cave-earth, with pebbles and some angular stones, from two to thirteen feet thick, containing the bones of Elephants, Rhinoceros, Bears, Hyaenas, Felis, Reindeer, Horses, Oxen, and several Rodents; and, lastly, a layer of gravel, and rounded pebbles without fossils, underlaid the cave-earth and formed the lowest deposit.
In these beds no human bones were found, but in almost every part of the bone-bed were flint-knives, one of the most perfect being found thirteen feet down in the bone-bed, at its lowest part. The most remarkable fact in connection with this cave was the discovery of an entire left hind-leg of the Cave-bear lying in close proximity to this knife; ”not washed in a fossil state out of an older alluvium, and swept afterwards into this cave, so as to be mingled with the flint implements, but having been introduced when clothed in its flesh.” The implement and the Bear's leg were evidently deposited about the same time, and it only required some approximative estimate of the date of this deposit, to settle the question of the antiquity of man, at least in an affirmative sense.
Mr. H. W. Bristow, who was sent by the Committee of the Royal Society to make a plan and drawings of the Brixham Cave, found that its entrance was situated at a height of ninety-five feet above the present level of the sea. In his Report made to the Royal Society, in explanation of the plan and sections, Mr. Bristow stated that, in all probability, at the time the cave was formed, the land was at a lower level to the extent of the observed distance of ninety-five feet, and that its mouth was then situated at or near the level of the sea.
The cave consisted of wide galleries or pa.s.sages running in a north and south direction, with minor lateral pa.s.sages branching off nearly at right angles to the main openings--- the whole cave being formed in the joints, or natural divisional planes, of the rock.
The mouth or entrance to the cave originated, in the first instance, in an open joint or fissure in the Devonian limestone, which became widened by water flowing backwards and forwards, and was partly enlarged by the atmospheric water, which percolated through the cracks, fissures, and open joints in the overlying rock. The pebbles, forming the lowest deposit in the cave, were ordinary s.h.i.+ngle or beach-gravel, washed in by the waves and tides. The cave-earth was the residual part of the limestone rock, after the calcareous portion had been dissolved and carried away in solution; and the stalact.i.te and stalagmite were derived from the lime deposited from the percolating water.
With regard to bone-caves generally, it would seem that, like other such openings, they are most common in limestone rocks, where they have been formed by water, which has dissolved and carried away the calcareous ingredient of the rock. In the case of the Brixham cave, the mode of action of the water could be clearly traced in two ways: first, in widening out the princ.i.p.al pa.s.sages by the rush of water backwards and forwards from the sea; and, secondly, by the infiltration and percolation of atmospheric water through the overlying rock. In both cases the active agents in producing the cave had taken advantage of a pre-existing fissure or crack, or an open joint, which they gradually enlarged and widened out, until the opening received its final proportions.
The cave presented no appearance of ever having been inhabited by man; or of having been the den of Hyaenas or other animals, like Wookey Hole in the Mendips, and some other bone-caves. The most probable supposition is, that the hind quarter of the Bear and other bones which were found in the cave-earth, had been washed into the cave by the sea, in which they were floating about.
We draw some inferences of the greatest interest and significance from the Brixham cave and its contents.
We learn that this country was, at one time, inhabited by animals which are now extinct, and of whose existence we have not even a tradition; that man, then ignorant of the use of metal, and little better than the brutes, was the contemporary of the animals whose remains were found in the cave, together with a rude flint-implement--the only kind of weapon with which our savage ancestor defended himself against animals scarcely wilder than himself.
We also learn that after the cave had been formed and sealed up again, as it were, together with all its contents, by the deposition of a solid crust of stalagmite--an operation requiring a very great length of time to effect--the Reindeer (_Cervus Tarandus_) was indigenous to this country, as is proved by the occurrence of an antler of that animal which was found lying upon, and partly imbedded in, the stalagmite forming the roof or uppermost, that is, the latest formed, of the cave-deposits.
Lastly, we learn that, at the time the cave was formed, and while the land was inhabited by man, that part of the country was lower by ninety-five feet than it is now; and that this elevation has probably been produced so slowly and so gradually, as to have been imperceptible during the time it was taking place, which extended over a vast interval of time, perhaps over thousands of years.
Perhaps it may not be out of place here to describe the mode of formation of bone-caves generally, and the causes which have produced the appearances these now present.
Caves in limestone rocks have two princ.i.p.al phases--one of formation, and one of filling up. So long as the water which enters the cavities in the course of formation, and carries off some of the calcareous matter in solution, can find an easy exit, the cavity is continually enlarged; but when, from various causes, the water only enters in small quant.i.ties, and does not escape, or only finds its way out slowly, and with difficulty, the lime, instead of being removed, is re-deposited on the walls, roof, sides, and floor of the cavity, in the form of stalact.i.tes and stalagmite, and the work of re-filling with solid carbonate of lime then takes place.
Encouraged by the Brixham discoveries, a congress of French and English geologists met at Amiens, in order to consider certain evidence, on which it was sought to establish as a fact that man and the Mammoth were formerly contemporaries.
The valley of the Somme, between Abbeville and Amiens, is occupied by beds of peat, some twenty or thirty feet deep, resting on a thin bed of clay which covers other beds, of sand and gravel, and itself rests on white Chalk with flints. Bordering the valley, some hills rise with a gentle slope to a height of 200 or 300 feet, and here and there, on their summits, are patches of Tertiary sand and clay, with fossils, and again more extensive layers of loam. The inference from this geological structure is that the river, originally flowing through the Tertiary formation, gradually cut its way through the various strata down to its present level. From the depth of the peat, its lower part lies below the sea-level, and it is supposed that a depression of the region has occurred at some period: again, in land lying quite low on the Abbeville side of the valley, but above the tidal level, marine sh.e.l.ls occur, which indicate an elevation of the region; again, about 100 feet above the valley, on the right bank of the river, and on a sloping surface, is the Moulin-Quignon, where shallow pits exhibit a floor of chalk covered by gravel and sand, accompanied by gravel and marly chalk and flints more or less worn, well-rounded Tertiary flints and pebbles, and fragments of Tertiary sandstone. Such is the general description of a locality which has acquired considerable celebrity in connection with the question of the antiquity of man.
The Quaternary deposits of Moulin-Quignon and the peat-beds of the Somme formerly furnished Cuvier with some of the fossils he described, and in later times chipped flint-implements from the quarries and bogs came into the possession of M. Boucher de Perthes; the statements were received at first not without suspicion--especially on the part of English geologists who were familiar with similar attempts on their own credulity--that some at least of these were manufactured by the workmen of the district. At length, the discovery of a human jaw and tooth in the gravel-pits of St. Acheul, near Amiens, produced a rigorous investigation into the facts, and it seems to have been established to the satisfaction of Mr. Prestwich and his colleagues, that flint-implements and the bones of extinct Mammalia are met with in the same beds, and in situations indicating very great antiquity. In the sloping and irregular deposits overlooking the Somme, the bones of Elephants, Rhinoceros, with land and fresh-water sh.e.l.ls of existing species, are found mingled with flint-implements. Sh.e.l.ls like those now found in the neighbouring streams and hedge-rows, with the bones of existing quadrupeds, have been obtained from the peat, with flint-tools of more than usual finish, and together with them a few fragments of human bones. Of these reliquiae, the Celtic memorials lie below the Gallo-Roman; above them, oaks, alders, and walnut trees occur, sometimes rooted, but no succession of a new growth of trees appear.
The theory of the St. Acheul beds is this: they were deposited by fluviatile action, and are probably amongst the oldest deposits in which human remains occur, older than the peat-beds of the Somme--but what is their _real_ age? Before submitting to the reader the very imperfect answer this question admits of, a glance at the previous discoveries, which tended to give confirmation to the observations just narrated, may be useful.
<script>