Here man, whose presence is attested by worked flints of various forms, by weapons and instruments of bone, by phalanges of reindeer made into whistles, lived with the reindeer, the glutton, and the polar fox, and gathered mosses which are now confined to Northern Europe, such as Hypnum sarmentosum, fluitans, and aduncum. As in Denmark, he seems to have followed the glaciers step by step, as the melting of the latter opened out new lands to his activity.

IV. Without claiming such accuracy for the historic dates, or even such an approximation as that derived from the Aryan traditions on the most ancient monuments of Egypt, is it possible to estimate the number of years which have elapsed since the times we have just been discussing?

This question has often attracted the attention of geologists and anthropologists, and several attempts have been made to solve it. But the results are still far from being satisfactory. They are none the less interesting, and calculated, to a certain extent, to encourage fresh research. The method is good; it has only been hitherto wanting in sufficiently precise dates, and we may hope that they will be sooner or later forthcoming.

This method is easily comprehended. For example, let us admit that the peat has a regular growth in the skovmoses, and suppose, in addition, that a coin, recognised as belonging to the twelfth century, has been found at a depth of 1.50 metres (49 feet); we shall conclude that the layer of peat has only required about 600 years for its formation. The age of a bronze hatchet found at greater depth, 8 metres (26-24 feet), will be given by the proportion 1m 50:6:: 8m: x. The hatchet would then be 3,200 years old, and would date from the fourteenth century before our era.

Many natural phenomena are available for calculations of this kind. Such are the alluvium of a river, the silting up of a lake, the erosion of a hill or plateau, etc. But in order that the results of these calculations may have a real value, the phenomenon which serves as the basis, and the calcula

tions resulting from the data must satisfy three conditions which have been very clearly stated by M. Forel.

1. The phenomenon should be perfectly constant and regular, which is never the case. At least, it ought to be possible to regard its action as giving an annual mean or constant centennial result, by means of compensations which are produced naturally.

2. When super-imposed strata are used as a means of estimation, the age of the strata serving as a term of comparison, ought to be rigorously determined; the nature of the objects compared should leave no doubt.

3. We ought to be certain that the objects found in any stratum really belong to it, that they have not been displaced by any reformation or by their mere weight. (Peat.)

Should even one only of these conditions be unfulfilled, the calculation is necessarily erroneous. Now, hitherto, we cannot be absolutely certain that the conditions laid down by M. Forel are satisfied. Nevertheless, I repeat, it is interesting to know what results have been obtained by these attempts at prehistoric chronology.

It would seem, at first sight, that the skovmoses must be useful for researches of this kind. It is not so. Steenstrup, an excellent judge of these matters, after having estimated at forty centuries the time necessary for the formation of the peat accumulated in these bogs, declares that it might be twice, or even four times as much.

In reality, the uncertainty as to the results obtained from the growth of peat, is very much greater than the Danish savant admits. In adding to the data collected by Brandt, those kindly presented to me by my colleague, M. Bésal, I find that for a period of 443 years the mean annual growth of peat is 0.032 metre (1.26 inch). But this mean is the result of numbers whose extremes are 0.065 metre (2.56 inch) and 00065 metre (0.26 inch). That is to say, that the means found by different observers for the annual growth of peat, vary from one to ten.

The calculations of MM. Gillieron and Troyon, resting upon

the deposition of silt, which has caused the retreat of the Lakes of Bienne and Neuchâtel, have but little connection with the present subject. Both have sought to determine the age of the Lake dwellings, which belong, probably, to a much later period than the one which we are now endeavouring to determine. We may, however, notice the numbers, 6,000 years and 3,300 years, found by these observers.

The chronological results derived from the littoral accumulation of silt, of which I have just spoken, exhibit chances for error which Vogt has rightly pointed out. For some time the results have been thought more worthy of confidence which were based upon the researches made by M. Morlot upon the conical accumulation of silt deposited by the Tinière. This cone, which was cut through by the railway for a distance of 133 (436 feet), and to a depth of 7.7m (25 feet), exhibited in the midst of the mass of gravel three undisturbed soils, the highest of which contained Roman instruments and coins; the second, pottery of the Bronze age; and the third, split bones, charcoal, and different objects referable to the close of the Stone age. Fixing the commencement of the Roman period in Switzerland at the first century of our era, and the end of it at the year 563, and making some corrections which cannot be detailed here, M. Morlot has considered himself able to propose the following numbers as approximate dates:

These numbers are not high. The number given by M. Morlot as the age of the Stone period in Switzerland, leads us back to an antiquity which does not exceed that given by the Egyptian monuments; and it is impossible to avoid being struck with the differences of civilization exhibited by the two countries. Nevertheless, this fact cannot constitute a reason for doubting the results of the Swiss savant. It is well known that man during the same time has not every

where equally advanced in civilization, and that the Eskimas are still in the Neolithic period.

But other criticisms have been brought forward against M. Morlot, the result of which is that the numbers furnished by the cone of the Tinière cannot be accepted as giving a real approximation to the date which we are seeking for.

V. M. Forel, who has taken an active part in this discussion, has tried to solve the problem in an indirect way. Instead of seeking directly for the age of a prehistoric fact, he has proposed to have recourse to the rule of false position, which allows the determination either of a maximum which the numbers cannot possibly exceed, or a minimum below which they cannot fall. He has applied this plan, which is as correct as it is ingenious, to the Lake of Geneva.

It is well known that the waters of the Rhone, especially during the floods caused by the melting of the snow, enter the lake in a very turbid condition, and flow on remarkably clear. The mud thus deposited evidently tends to fill up the lake, and has already silted up a part of the great depression which was filled by the ice of the Quaternary epoch. M. Forel has first determined the annual volume of the deposit. He has then calculated the volume of the present lake, basing his calculations on the soundings made by La Bèche. He has thus been enabled to calculate the time necessary for the sediment of the Rhone to fill up the entire lake. Then, admitting that the part of the original lake already filled up had a mean depth equal to that of the present lake, he has compared the surface of the alluvial deposits already formed with the surface of the lake itself. The proportion is almost one to three. These deposits have then been formed in a third of the time necessary to fill up the present lake. Now their formation commenced immediately after the retreat of the glaciers. The date thus obtained is, then, that of the modern geological epoch.

Such is the method by which M. Forel arrives at the number of 100,000 years. This is a maximum which is probably much exaggerated. M. Forel shows this himself

very clearly. He has always taken the lowest numbers for the estimation of the increase of alluvium; he has considered on the whole year ninety days only as contributing to this increase; he has only included the Rhone in this estimation, and taken no account of other rivers, streams, etc.; he has not taken into consideration inundations, extraordinary falls of rain, landslips, etc. ; he has assumed the floods of the Rhone have always resembled the present floods, while they must originally have been much more considerable, and have carried away much more material from mountain slopes but recently relieved from their covering of ice; he has said nothing of the gravel and sand which must necessarily be carried along the bed of a rapid stream like the Rhone, etc.

M. Forel's result must therefore undergo serious reduction before it approximates to the truth. Without attempting a precise statement, we can (at least) admit with almost absolute certainty that the present geological epoch commenced less than 100,000 years ago.

On the other hand, M. Arcelin has sought for a solution of the same problem in the deposits of the Saône. The present river flows in a channel hollowed out in the alluvium of the Saône of Quaternary times, the banks of which have been raised by the sediment deposited during floods. The two deposits are very easily distinguished. The homogeneity of the modern alluvium indicates, moreover, a remarkably regular phenomenon. The banks of the Saône at different points form more or less abrupt hills which constitute so many natural geological sections. The erosions of the river have laid bare objects easily recognised as belonging to the Roman period, the Bronze age, and the Neolithic age. These objects are found at a constant height, showing that they are in situ. The hills of the Saône, then, constitute one of those means of estimating prehistoric chronology, which are so valuable to us. MM. Arcelin and De Ferry have attempted first to determine the age of the different layers. The numbers so obtained show a certain amount of discordance, undoubtedly due to the fact that M. de