Chapter 16

[EI]Bulletin of the Geological Society of America, vol. ii, pp. 196, 197.

This view of Mr. Becker is amply sustained by many other obvious facts, some of which may be easily observed by tourists who visit the Yosemite Park. The freedom of the abutting walls of this cañon from talus, as well as the freshness of the glacial scratches upon both the walls and the floor of the tributary cañons, all indicate a lapse of centuries only, rather than of thousands of years, since their occupation by glacial ice.

The freshness of the high-level terraces surrounding the valleys of Great Salt Lake, in Utah, and of Pyramid and North Carson Lakes, in Nevada, and the small amount of erosion which has taken place since the formation of these terraces, point in the same direction—namely, to a very recent date for the glaciation of the Pacific coast.

We have already detailed the facts concerning the formation of these terraces and the evidence of their probable connection with the Glacial period. It is sufficient, therefore, here to add that, according to Mr. Russell and Mr. Gilbert (two of the most eminent members of the United States Geological Survey, who have each published monographs minutely embodying the results of their extensive observations in this region), the erosion of present streams in the beds which were deposited during the enlargement of the lakes is very slight, and the modification of the shores since the formation of the high terraces has been insignificant.

According to Mr. Gilbert: "The Bonneville shoresare almost unmodified. Intersecting streams, it is true, have scored them and interrupted their continuity for brief spaces; but the beating of the rain has hardly left a trace. The sea-cliffs still stand as they first stood, except that frost has wrought upon their faces so as to crumble away a portion and make a low talus at the base. The embankments and beaches and bars are almost as perfect as though the lake had left them yesterday, and many of them rival in the symmetry and perfection of their contours the most elaborate work of the engineer. There are places where boulders of quartzite or other enduring rock still retain the smooth, glistening surfaces which the waves scoured upon them by clashing against them the sands of the beach.

“When this preservation is compared with that of the lowest Tertiary rocks of the region—the Pliocene beds to which King has given the name Humboldt—the difference is most impressive. The Pliocene shore-lines have disappeared.

“The deposits are so indurated as to serve for building-stone. They have been upturned in many places by the uplifting of mountains. Elsewhere they have been divided by faults, and the fragments, dissevered from their continuation in the valley, have been carried high up on the mountain-flanks, where erosion has carved them in typical mountain forms.... The date of the Bonneville flood is the geologic yesterday, and, calling it yesterday, we may without exaggeration refer the Pliocene of Utah to the last decade; the Eocene of the Colorado basin to the last century, and relegate the laying of the Potsdam sandstone to prehistoric times.”[EJ]

[EJ]Second Annual Report of the United States Geological Survey, p. 188.

Mr. Russell adds to this class of evidence that of the small extent to which the glacial striæ have been effacedsince the withdrawal of the ice from the borders of these old lakes: “The smooth surfaces are still scored with fine, hair-like lines, and the eye fails to detect more than a trace of disintegration that has taken place since the surfaces received their polish and striation.... It seems reasonable to conclude that in a severe climate like that of the high Sierra it” (the polish) “could not remain unimpaired for more than a few centuries at the most.”[EK]

[EK]See also Mr. Upham in American Journal of Science, vol. xli, pp. 41, 51.

Europe does not seem to furnish so favourable opportunities as America for estimating the date of the Glacial period; still it is not altogether wanting in data bearing upon the subject.

Some of the caves in which palæolithic implements were found associated with the bones of extinct animals in southern England contain floors of stalagmite which have been thought by some to furnish a measure of the time separating the deposits underneath from those above. This is specially true in the case of Kent’s Cavern, near Torquay, which contains two floors of stalagmite, the upper one almost continuous and varying in thickness from sixteen inches to five feet, the lower one being in places twelve feet thick, underneath which human implements were found.

But it is difficult to determine the rate at which stalagmite accumulates. As is well known, this deposit is a form of carbonate of lime, and accumulates when water holding the substance in solution drops down upon the surface, where it is partially evaporated. It then leaves a thin film of the substance upon the floor. The rate of the accumulation will depend upon both the degree to which the water is saturated with the carbonate and upon the quantity of the water which percolates through the roof of the cavern. These factors are so variable, and so dependentupon unknown conditions in the past, that it is very difficult to estimate the result for any long period of time. Occasionally a quarter of an inch of stalagmite accretion has been known to take place in a cavern in a single year, while in Kent’s Cavern, over a visitor’s name inscribed in the year 1688, a film of stalagmite only a twentieth of an inch in thickness has accumulated. If, therefore, we could reckon upon a uniformity of conditions stretching indefinitely back into the past, we could determine the age of these oldest remains of man in Kent’s Hole by a simple sum in arithmetic, and should infer that the upper layer of stalagmite required 240,000 years, and the lower 576,000 years, for their growth, which would carry us back more than 700,000 years, and some have not hesitated to affix as early a date as this to these lowest implement-bearing gravels.

But other portions of the cave show an actual rate of accretion very much larger. Six inches of stalagmite is there found overlying some remains of Romano-Saxon times which cannot be more than 2,000 years old. Assuming this as the uniform rate, the total time required for the deposit of the stalagmitic floors would still be about 70,000 years. But, as we have seen, the present rates of deposition are probably considerably less than those which took place during the moister climate of the Glacial epoch. Still, even by supposing the rate to be increased fourfold, the age of this lower stratum would be reduced to only 12,000 years. So that, as Mr. James Geikie well maintains, “Even on the most extravagant assumption as to the former rate of stalagmitic accretion, we shall yet be compelled to admit a period of many thousands of years for the formation of the stalagmitic pavements in Kent’s Cavern.”[EL]We should add, however, that there is much well-founded doubt whether the implements found in thelowest stratum were really in place, since, according to Dr. Evans, “Owing to previous excavations and to the presence of burrowing animals, the remains from above and below the stalagmite have become intermingled.”[EM]

[EL]Prehistoric Europe, p. 83.

[EM]Stone and Flint Implements, p. 446.

An attempt was made by M. Morlot in Switzerland to obtain the chronology of the Glacial period by studying the deltas of the streams descending the glaciated valleys. He paid special attention to that of the Tinière, a stream which flows into Lake Geneva near Villeneuve. The modern delta of this stream consists of gravel and sand deposited in the shape of a flattened cone, and investigations upon it were facilitated by a long railroad cutting through it. “Three layers of vegetable soil, each of which must at one time have formed the surface of the cone, have been cut through at different depths.”[EN]In the upper stratum Roman tiles and a coin were found; in the second stratum, unvarnished pottery and implements of bronze; while in the lower stratum, at a depth of nineteen feet from the surface, a human skull was found, to which Morlot assigned an age of from 5,000 to 7,000 years.

[EN]Lyell’s Antiquity of Man, p. 28.

But Dr. Andrews, after carefully revising the data, felt confident that the time required for the whole deposit of this lower delta was not more than 5,000 years, and that the oldest human remains in it, which were about half way from between the base and the surface of the cone, were probably not more than 3,000 years old.

Still, the significance of this estimate principally arises from the relation of the modern delta to older deltas connected with the Glacial period. Above this modern delta, formed by the river in its present proportions, there is another, more ancient, about ten times as large, whose accumulation doubtless took place upon the final retreat of the ice from Lake Geneva. No remains of man have beenfound in this, but it doubtless corresponds in age with the high-level gravels in the valley of the Somme, in which the remains of man and the mammoth, together with other extinct animals, have been found.

We do not see, however, that any very definite calculation can be made concerning the time required for its deposition. Lyell was inclined to consider it ten times as old as the modern delta, simply upon the ground of its being ten times as large. On Morlot’s estimate of the age of the modern delta, therefore, the retreat of the ice whose melting torrents deposited the upper delta would be fixed at 100,000 years ago, and upon Dr. Andrews’s calculation, at about 20,000.

But it is evident that the problem is not one of simple multiplication. The floods of water which accompanied the melting back of the ice from the upper portions of this valley must have been immensely larger than those of the present streams, and their transporting power immensely greater still. Hence we do not see that any conclusions can be drawn from the deltas of the Tinière to give countenance to extreme views concerning the date of the close of the Glacial period.[EO]

[EO]Lyell’s Antiquity of Man, p. 321.

In the valley of the Somme the chronological data relating to the Glacial period, and indicating a great antiquity for man, have been thought to be more distinct than anywhere else in Europe. As already stated, it is the prevalent opinion that since man first entered the valley, in connection with the mammoth and the other extinct animals characteristic of the Glacial period, the trough of the Somme, about a mile in width and a hundred feet in depth, has been eroded by the drainage of its present valley. An extensive accumulation of peat also has taken place along the bottom of the trough of the river since it was originally eroded to its present level.This substance occurs all along the bottom of the valley from far above Amiens to the sea, and is in some places more than thirty feet in depth. The animal and vegetable remains in it all belong to species now inhabiting Europe.

The depth of the peat indicates that when it was formed the land stood at a slightly higher elevation than now, for the base of the stratum is now below the sea-level, while the peat is of fresh-water origin, and, according to Dr. Andrews,[EP]is formed from the vegetable accumulations connected with forest growths. When, therefore, the country was covered with forests, as it was in prehistoric times, the accumulation must have proceeded with considerable rapidity. This inference is confirmed by the occurrence in the peat of prostrate trunks of oak, four feet in diameter, so sound that they were manufactured into furniture. The stumps of trees, especially of the birch and alder, were also found in considerable number, standing erect where they grew, sometimes to a height of three feet. Now, as Dr. Andrews well remarks, it is evident that, in order to prevent these stumps and prostrate trunks from complete decay, the accumulation of peat must have been rapid. From certain Roman remains found six feet and more beneath the surface, he estimates that the accumulation since the Roman occupation has been as much as six inches a century, at which rate the whole would take place in somewhat over 5,000 years.

[EP]American Journal of Science, October, 1868.

Still, if we accept this estimate, we have obtained but a starting-point from which to estimate the age of the high-level gravels in which palæolithic implements were found; for, if we accept the ordinary theory, we must add to this the time required for the river to lower its bed from eighty to a hundred feet, and to carry out to the sea the contents of its wide trough. But, as already shown,the Glacial period was, even in the north of France, a time of great precipitation and of a considerable degree of cold, when ice formed to a much greater extent than now upon the surface of the Somme. The direct evidence of this consists in the boulders mingled with the high-level gravel which are of such size as to require floating ice for their transportation.

In addition to the natural increase in the eroding power of the Somme brought about by the increase in its volume, on account of the greater precipitation in the Glacial age, there would also be, as Prestwich has well shown, a great increase in rate through the action of ground-ice, which plays a very important part in the river erosion of arctic countries, and in all probability did so during the Glacial period in the valley of the Somme.

“When the water is reduced to and below 32° Fahr., although the rapid motion may prevent freezing on the surface for a time, any pointed surfaces at the bottom of the river, such as stones and boulders, will determine (as is the case with a saturated saline solution) a sort of crystallisation, needles of ice being formed, which gradually extend from stone to stone and envelop the bodies with which they are in contact. By this means the whole surface of a gravelly river-bed may become coated with ice, which, on a change of temperature, or of atmospheric pressure, or on acquiring certain dimensions and buoyancy, rises to the surface, bringing with it the loose materials to which it adhered. Colonel Jackson remarks, in speaking of this bottom-ice, that ‘it frequently happens that these pieces, in rising from the bottom, bring up with them sand and stones, which are thus transported by the current.... When the thaw sets in the ice, becoming rotten, lets fall the gravel and stones in places far distant from those whence they came.’

“Again, Baron Wrangell remarks that, ‘in all the more rapid and rocky streams of this district [northern Siberia]the formation of ice takes place in two different manners; a thin crust spreads itself along the banks and over the smaller bays where the current is least rapid; but the greater part is formed in the bed of the river, in the hollows among the stones, where the weeds give it the appearance of a greenish mud. As soon as a piece of ice of this kind attains a certain size, it is detached from the ground and raised to the surface by the greater specific gravity of the water; these masses, containing a quantity of gravel and weeds, unite and consolidate, and in a few hours the river becomes passable in sledges instead of in boats.’ Similar observations have been made in America; but instances need not be multiplied, as it is a common phenomenon in all arctic countries, and is not uncommon on a small scale even in our latitudes.

“The two causes combined—torrential river-floods and rafts of ground-ice, together with the rapid wear of the river cliffs by frost—constituted elements of destruction and erosion of which our present rivers can give a very inadequate conception; and the excavations of the valleys must have proceeded with a rapidity with which the present rate of erosion cannot be compared; and estimates of time founded on this, like those before mentioned on surface denudation, are therefore not to be relied upon.”[EQ]

[EQ]Prestwich’s Geology, vol. ii, pp. 471, 472.

Speaking a little later of taking the present rates of river erosion as a standard to estimate the chronology of the Glacial period, the same high authority remarks: "It no more affords a true and sufficient guide than it would be to take the tottering paces and weakened force of an old man as the measure of what that individual was, and what he could do, in his robust and active youth. It may be right to take the effects at present produced by a given power as the known quantity, a, but it is equally indispensable, in all calculations relative to the degree of thoseforces in past times, to take notice of the unknown quantity, x, although this, in the absence of actual experience, which cannot be had, can only be estimated by the results and by a knowledge of the contemporaneous physical conditions. It may be a complicated equation, but it is not to be avoided.[ER]

[ER]Prestwich’s Geology, vol. ii, pp. 520, 521.

“In this country and in the north of France broad valleys have been excavated to the depth of from about eighty to a hundred and fifty feet in glacial and post-glacial times. Difficult as it is by our present experience to conceive this to have been effected in a comparatively short geological term, it is equally, and to my mind more, difficult to suppose that man could have existed eighty thousand years or more, and that existing forms of our fauna and flora should have survived during two hundred and forty thousand years without modification or change.”[ES]

[ES]Ibid., p. 533.

The discussion of the age of the high-level river gravels of the Somme and other streams in northwestern Europe is not complete, however, without considering another possibility as to the mode of their deposition. The conclusion to which Mr. Alfred Tylor arrived, after a prolonged and careful study of the subject, was that the main valleys of the Somme and other streams in northern France and southern England were preglacial in their origin, and that the accumulations of gravel at high levels along their margin were due to enormous floods which characterised the closing portion of the great ice age, which he denominated the pluvial period.[ET]The credibility of floods large enough to accomplish the results manifest in the valley of the Somme is supported by reference to a flood which occurred on the Mulleer River, in India, in 1856, when astream, which is usually insignificant, was so swollen by a rainfall of a single day that it rose high enough to sweep away an iron bridge the bottoms of whose girders were sixty-five feet above high-water mark. One iron girder weighing eighty tons was carried two miles down the river, and nearly buried in sand. The significance of these facts is enhanced by observing also that for fifteen miles above the bridge the fall of the river only averaged ten feet per mile. Floods to this extent are not uncommon in India. During the Glacial period spring freshets, must have been greatly increased by the melting of a large amount of snow and ice which had accumulated during the winter, and also by the formation of ice-gorges near the mouths of many of the streams. It is probable, also, that the accumulation of ice across the northern part of the German Ocean may have permanently flooded the streams entering that body of water; for it is by no means improbable that there was a land connection between England and France across the Straits of Dover until after the climax of the Glacial period. In support of his theory, Mr. Tylor points to the fact “that the gravel in the valley of the Somme at Amiens is partly derived fromdébrisbrought down by the river Somme and by the two rivers the Celle and the Arve, and partly consists of material from the adjoining higher grounds washed in by land floods,” and that the “Quaternary gravels of the Somme are not separated into two divisions by an escarpment of chalk parallel to the river,” but “thin out gradually as they slope from the high land down to the Somme.”

Mr. Tylor’s reasoning seems especially cogent to one who stands on the ground where he can observe the size of the valley and the diminutive proportions of the present stream. Even if we do not grant all that is claimed by Mr. Tylor, it is difficult to resist the main force of his argument, and to avoid the conclusion that the valley of the Somme is largely the work of preglacial erosion, and has been, at any rate, only in slight degree deepened and enlarged during post-Tertiary time.

[ET]Proceedings of the Geological Society, London, November 8, 1867, pp. 103-126: Quarterly Journal of the Geological Society, February 1, 1869, pp. 57-100.

Summary.

In briefly summarising our conclusions concerning the question of man’s antiquity as affected by his known relations to the Glacial period, it is important, first, to remark upon the changes of opinion which have taken place with respect to geological time within the past generation. Under the sway of Sir Charles Lyell’s uniformitarian ideas, geologists felt themselves at liberty to regard geological time as practically unlimited, and did not hesitate to refer the origin of life upon the globe back to a period of 500,000,000 years. In the first edition of his Origin of Species Charles Darwin estimated that the time required for the erosion of the Wealden deposits in England was 306,662,400 years, which he spoke of as “a mere trifle” of that at command for establishing his theory of the origin of species through natural selection. In his second edition, however, he confesses that his original statement concerning the length of geological time was rash; while in later editions he quietly omitted it.

Meanwhile astronomers and physicists have been gradually setting limits to geological time until they have now reached conclusions strikingly in contrast with those held by the mass of English geologists forty years ago. Mr. George H. Darwin, Professor of Mathematics at Cambridge University, has from a series of intricate calculations shown that between fifty and one hundred million years ago the earth was revolving from six to eight times faster than now, and that the moon then almost touched the earth, and revolved about it once every three or four hours. From this proximity of the moon to the earth, it would result that if the oceans had been then in existence the tides would have been two hundred times as great as now, creating a wave six hundred feet in height, whichwould sweep around the world every four hours. Such a condition of things would evidently be incompatible with geological life, and geology must limit itself to a period which is inside of 100,000,000 years. Sir William Thomson and Professor Tait, of Great Britain, and Professor Newcomb, of the United States Naval Observatory, approaching the question from another point of view, seem to demonstrate that the radiation of heat from the sun is diminishing at a rate such that ten or twelve million years ago it must have been so hot upon the earth’s surface as to vaporise all the water, and thus render impossible the beginning of geological life until later than that period. Indeed, they seem to prove by rigorous mathematical calculations that the total amount of heat originally possessed by the nebula out of which the sun has been condensed would only be sufficient to keep up the present amount of radiation for 18,000,000 years.

The late Dr. Croll, feeling the force of these astronomical conclusions, thought it possible to add sufficiently to the sun’s heat to extend its rule backwards approximately 100,000,000 years by the supposition of a collision with it of another moving body of near its own size. Professor Young and others have thought that possibly the heat of the sun might have been kept up by the aid of the impact of asteroids and meteorites for a period of 30,000,000 years. Mr. Wallace obtains similar figures by estimating the time required for the deposition of the stratified rocks open to examination upon the land surface of the globe. As a result of his estimates, it would appear that 28,000,000 years is all the time required for the formation of the geological strata. From all this it is evident that geologists are much more restricted in their speculations involving time than they thought themselves to be a half-century ago. Taking as our standard the medium results attained by Wallace, we shall find it profitable to see how this time can be portionedout to the geological periods, that we may ascertain how much approximately can be left for the Glacial epoch.

On all hands it is agreed that the geological periods decrease in length as they approach the present time. According to Dana’s estimates,[EU]the “ratio for the Palæozoic, Mesozoic, and Cenozoic periods would be 12:3:1”—that is, Cenozoic time is but one sixteenth of the whole. This embraces the whole of the Tertiary period, during which placental mammals have been in existence, together with the post-Tertiary or Glacial period, extending down to the present time; that is, the time since the beginning of the Tertiary period and the existence of the higher animals is considerably less than two million years, even upon Mr. Wallace’s basis of calculation. But if we should be compelled to accept the calculations of Sir William Thomson, Professor Tait, and Professor Newcomb, the Cenozoic period would be reduced to considerably less than one million years. It is difficult to tell how much of Cenozoic time is to be assigned to the Glacial period, since there is, in fact, no sharply drawn line between the two periods. The climax of the Glacial period represented a condition of things slowly attained by the changes of level which took place during the latter part of the Tertiary epoch.

[EU]See revised edition of his Geology, p. 586.

In order to estimate the degree of credibility with which we may at the outset regard the theory of Mr. Prestwich and others, that all the phenomena of the Glacial period can be brought within the limits of thirty or forty thousand years, it is important to fix our minds upon the significance of the large numbers with which we are accustomed to multiply and divide geological quantities.[EV]

[EV]See Croll’s Climate and Time, chap. xx.

Few people realise either the rapidity with which geological changes are now proceeding or the small amount of change which might produce a Glacial period, and fewer still have an adequate conception of how long a period a million years is, and how much present geological agencies would accomplish in that time. At the present rate at which erosive agencies are now acting upon the Alps, their dimensions would be reduced one half in a million years. At the present rate of the recession of the Falls of St. Anthony, the whole gorge from St. Louis to Minneapolis would have been produced in a million years. A river lowering its bed a foot in a thousand years would produce a cañon a thousand feet deep in a million years.

If we suppose the Glacial period to have been brought about by an elevation of land in northern America and northern Europe, proceeding at the rate of three feet a century, which is that now taking place in some portions of Scandinavia, this would amount to three thousand feet in one hundred thousand years, and that is probably all, and even more than all, which is needed. One hundred thousand years, therefore, or even less, might easily include both the slow coming on of the Glacial period and its rapid close. Prestwich estimates that the ice now floating away from Greenland as icebergs is sufficient if accumulating on a land-surface to extend the borders of a continental glacier about four hundred and fifty feet a year, or one mile in twelve years, one hundred miles in twelve hundred years, and seven hundred miles (about the limit of glacial transportation in America) in less than ten thousand years.

After making all reasonable allowances, therefore, Prestwich’s conclusion that twenty-five thousand years is ample time to allow to the reign of the ice of the Glacial period cannot be regarded as by any means incredible or, ona priorigrounds, improbable.

APPENDIX.

THE TERTIARY MAN.

By Professor Henry W. Haynes.

“It must not be imagined that it is in any way proved that the Palæolithic man was the first human being that existed. We must be prepared to wait, however, for further and better authenticated discoveries before carrying his existence back in time further than the Pleistocene or post-Tertiary period.”[EW]This was the position assumed more than twelve years ago by the eminent English geologist and archæologist, Dr. John Evans, and it was still maintained in his address before the Anthropological Section of the British Association on September 18, 1890. I believe that the study of all the evidence in favor of the existence of the Tertiary man that has been brought forward down to the present time will leave the question in precisely the same state of uncertainty.

[EW]A Few Words on Tertiary Man, Trans, of Hertfordshire Nat. Hist. Soc, vol. i, p. 150.

“In order to establish the existence of man at such a remote period the proofs must be convincing. It must be shown, first, that the objects found are of human workmanship; secondly, that they are really found as stated; and, thirdly, the age of the beds in which they are found must be clearly ascertained and determined.”[EX]These tests I propose to apply to the evidence for the Tertiary man recently broughtforward in Europe, and then to consider the significance of certain discoveries on the Pacific coast of our own continent.

[EX]Ibid., p. 148.

Tertiary deposits in Europe are alleged to have supplied three sorts of evidence of this fact:First, the bones of man himself;second, bones of animals showing incisions or fractures supposed to have been produced by human agency;third, chipped flints believed to exhibit marks of design in their production.

A very complete survey of the question of the antiquity of man was published in 1883 by M. Gabriel de Mortillet, one of its most eminent investigators, under the title of Le Préhistorique. In that work he subjected to a most rigid examination all the evidence for Tertiary man, coming under either of these three heads, that had been brought forward up to that date.

The instances of the discovery of human bones in Europe were two—at Colle del Vento, in Savona, and Castenedolo, near Brescia, both in Italy. At the former site, in a Pliocene marine deposit abounding in fossil oysters and containing somescatteredbones of fossil mammals, a human skeleton was foundwith the bones lying in their natural connection. Mortillet, however, and many others regard this as an instance of a subsequent interment rather than as proof that the man lived in Pliocene times.[EY]At Castenedolo, in a similar marine Pliocene formation, on three different occasions human skeletons have been discovered, but in different strata. One investigator has accounted for these as the result of a shipwreck in the Pliocene period. This bold hypothesis not only requires that man should have been sufficiently advanced at that very remote period to have navigated the sea, but it calls for two shipwrecks, at different times, at the same point. It has, however, since been abandoned by its author in favor of the presumption of subsequent interments, as in the previous instance.[EZ]

[EY]This is also the opinion of Hamy,Précis de Paléontologie Humaine, p. 67. Professor Le Conte,Elements of Geology(third edition, 1891), p. 609, is wrong in attributing the opposite conclusion to Hamy, on the evidence of “flint implements found in this locality.”

[EZ]Bullettino di Paletnologia Italiana, tome xv, p. 109 (August 18, 1889).

Animal bones showing cuts or breaks supposed to be the work of man have been found in seventeen different localities in Europe. They can all, however, be accounted for as the result of natural movements or pressure of the soil acting in connection with sharp substances, like fractured flints, or else as having been made by the teeth of sharks, whose fossil remains are found in great abundance in the same formation.

All the discoveries of flints supposed to show traces of intentional chipping are pronounced to be unsatisfactory, with the exception of those found in three localities—Thenay (near Tours) and Puy-Courny (near Aurillac), in France, and Otta, in the valley of the Tagus, in Portugal. As European archæologists at the present time are substantially in accord with Mortillet in restricting the discussion to these three places, I will follow their example. But although Mortillet believes that flints found at all these localities exhibit marks of intelligent action, he will not admit that they are the work of man. He attributes them to an intelligent ancestor of man, whom he calls by the name of anthropopithecus, or the precursor of man. Of this creature he distinguishes three different species, named respectively after the discoverers of the flints in the three localities just mentioned. The precursor, however, has found up to this time only a very limited acceptance among men of science, although a few believe in him on purely theoretical grounds. The discussion generally turns upon the question whether these flints were chipped intentionally or are the result of natural causes; and also upon the determination of the geological age of the formations in which they are found.

Fig. 108.—Flint flakes collected by Abbé Bourgeois from Miocene strata at Thenay (after Gaudry). Natural size.

I visited Thenay, the most celebrated of these three localities, in 1877, and had the advantage of studying the question there under the guidance of the late Abbé Bourgeois, the discoverer of the flints, and one of the most prominent advocates of the Tertiary man. This was the year before he died, and he showed me at the time his complete collection, and gave me several of the objects he had discovered. Geologists are agreed in assigning the deposits in which they occur to the lower Miocene or middle Tertiary period, which restricts the discussion to the character of the flintsthemselves. The accompanying woodcut[FA]gives some indication of their appearance, although it is misleading, because the long figure resembling a flint knife is intended to represent a solid nucleus. None of these objects, however, ought to be called “flints flakes,” as very few, if any, flakes showingthe “bulb of percussion,” always seen upon them, have been discovered in the Tertiary deposits at Thenay,[FB]although I have found them there myselfupon the surface. The three other figures would be classed by archæologists as “piercers,” as Bourgeois has himself designated them, and are also solid objects. Many of the Thenay flints exhibit a “crackled” appearance, due to the action of heat. On this account Mortillet maintains that they were splintered by fire, and not formed by percussion, the usual method by which flint implements were fabricated in the stone age. The Thenay objects are all of very small dimensions, and are so absolutely unlike the large, rudely-chipped axes of the Chellean type, found in so many different parts of the world, and generally accepted as the implement used by Palæolithic man, that the question naturally suggests itself, What could have been the purpose for which these little implements were employed? No better answer has been suggested than the ludicrous one that they were used by the hairy anthropopithecus to rid himself of the vermin with which he was infested.

[FA]From Le Conte,op. cit., p. 608. The figures are copied from Gaudry, who borrowed them from the article by Bourgeois,Congrès Internat. de Bruxelles, 1872, p. 89, pl. ii; and from hisLa Question de l’Homme Tertiare. Revue des Questions Scientifiques, 1877, p. 15.

[FB]Le Préhistorique, p. 91.

But, leaving aside the question of their purpose, let us consider the evidence presented by the flints themselves. Do they exhibit the unmistakable traces of intentional chipping produced by a series of slight blows or thrusts, delivered in regular succession and in the same direction, with the result of forming a distinctly marked edge? And does the appearance of the action of fire upon their surface imply the intervention of intelligence? To both questions M. Adrien Arcelin, the well-known geologist of Mâcon, has given very sufficient replies in the negative. He has discovered numerous objects of precisely similar appearance in Eocene deposits in the neighborhood of Mâcon.[FC]But, instead of pushing man back on this account so much further into the past, he accounts for the marks of chipping to be seen on many of these objects as the result of the accidental shocks of one stone against another in the countlessoverturnings and movements to which the strata have been subjected during the long ages of geological time. He gives photographs of some of these objects, which are to me entirely convincing, and describes how he has surprised Nature in the very act of fabricating them in an abandoned quarry worked in an Eocene deposit. He thinks the “crackled” surfaces can be readily explained as the result of atmospheric action, or of hot springs charged with silex. Numerous examples of similar changes in the surface of flint, that have been noticed by himself and others in different localities, are instanced. Even if some have been caused by fire, this does not necessarily imply the intervention of man to have produced it. Similar discoveries have also been made by M. d’Ault de Mesnil, at Thenay, in Eocene deposits,[FD]and by M. Paul Cabanne, in the Gironde.[FE]My own opinion, based upon the experience of many years spent in the study of flints broken naturally as well as artificially, and upon a careful examination of Bourgeois’s collections, is that the so-called Thenay flints are the result of natural causes.

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