Everything shows that the relics of man are here in a secondary _situs_, deposited in the same way as the bones of extinct animals and the whole geological material in which everything is embedded. That is the reason why the finds cannot be more exactly dated. They doubtless belong to the general drift, but whether to the Postglacial Period, or the warmer Interglacial Period, cannot be decided. The fauna admits of no absolute limitation, owing to its being mixed from both periods. The mammalia most frequently found in the strata in question are the mammoth, Siberian rhinoceros, horse, reindeer, ure-ox, giant fallow-deer, cave-lion, and cave-hyena. In very similar Drift deposits of the Somme near Amiens traces of man were found beside the bones of the hippopotamus and the elephant. These animals were chiefly prevalent in France and Germany in the Preglacial and Interglacial Periods of the Drift. Part of the animal remains found near Abbeville, particularly those of the cave-lion and cave-hyena, also point to the warmer Interglacial Period; on the other hand, the mammoth, Siberian rhinoceros, and especially the reindeer, appear to indicate with all certainty the second Glacial and Postglacial Periods. The bones of the older Drift animals may have been washed out of other primary _situs_; the reindeer had certainly already taken possession of those parts of France when the relics of man were embedded. [Illustration: Lyell Cuvier Boucher De Perthes THE OVERTHROW OF A FAMOUS THEORY OF THE ORIGIN OF THE EARTH AND MAN When Cuvier was supreme among geologists his theory that the great geological ages ended with sudden catastrophes which annihilated all life, and that all life was then created afresh, was universally accepted. One result of this theory was the disbelief in the existence of man before the Glacial Age. Boucher de Perthes sought to establish the former existence of Drift Man on finding human relics in the Somme Valley; but not until Sir Charles Lyell threw his influence on the side of De Perthes was the Preglacial existence of man admitted, and the long-accepted theory of Cuvier overthrown. ] In spite of the most eager search for similar relic-beds affording sure evidence of Drift Man, only a very few have as yet been discovered that can be placed by the side of those in the Somme valley. Two are in Germany, and are the more valuable as a more exact date can be given to them within the Drift Period. One is near Taubach (Weimar), the other at the source of the Schussen. The one at Taubach belongs to the Interglacial Period, that at the source of the Schussen to the Postglacial Period. The former lies on the moraines of the first Glacial Period, which was followed by the Interglacial Period; the latter on the moraines of the second Glacial Period, which slowly passed into the Postglacial Period. [Sidenote: The Climate of the Ice Age]