This fact is again proved by the discovery of a human station, made by M. Fraas, at Schussenried in Wurtemberg. 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 (4·9 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 l^m·50 : 6 :: 8^m : 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. Put in order that the results of these calculations may have a real value, the phenomenon which serves as the basis, and the calculations 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._)