Among the river deposits which have yielded relics of man's works of special interest are the stations of Chelles and Levallois, near Paris, and the gravels of Mauer, near Heidelberg.
The large amount of archæological materials recovered from these and other stations, too numerous to be here mentioned, represent a vast period of time covering at least one inter-glacial warm period, and a subsequent recrudescence of another ice age, with its accompanying Arctic climate. On the retreat of the last mer de glâce the climate became gradually ameliorated, and ultimately merged in that of the historic period. Coincident with these changes in the climate and physical geography of Europe since man appeared on the scene, the flora and fauna of the country, which are so dependent on a uniform environment for the stability of their racial characters, could not fail to have been greatly modified. The result was the bringing together into Central Europe of a number of species of animals representing faunas so widely apart as those of subtropical and Arctic regions. But this intermingling of animals from different quarters did not take place in a haphazard manner, but was effected in strict accordance with the exigencies of the cosmic environment. As man appeared in Western Europe during a warm inter-glacial period and lived on through a subsequent climate of Arctic severity, we have evidence to show that a succession of animals adapted for such climatal changes were his contemporaries.
