While the remains of the woolly mammoth are found here, there are also indications of the presence of a well-marked temperate flora. These high-level 'river-drifts' along the Thames(18) were certainly deposited when the climatic conditions were temperate, but they are succeeded by deposits indicating a renewed cold period, which may represent the cold 'full Mousterian' times of the Lower Palæolithic habitation of the Thames. Here we find the remarkable sheets of contorted 'drift' attributable to the movements of the frozen soil and subsoil when exposed to the heat of the summer sun. At the same time there may have been deposited along the Thames the alluvial loams and gravels, occasionally containing stones and rocks, which were brought down by ice-rafts; these low-level gravels are not to be confused with the underlying 'old river-gravels' which contain the warm temperate hippopotamus fauna, for they were accumulated under very cold conditions; they yield remains of the woolly rhinoceros and of the mammoth. Thus, on the high levels of the Thames as well as on the low levels we find evidences of the human culture and of the extinct fauna of the period of the fourth great glaciation. [Illustration: FIG. 100. Mousterian cavern of Wildkirchli. After Bächler. Entrances indicated at 1, 2, and 3, in the side of the limestone cliff. Here, at a height of 4,500 feet above sea-level, Bächler discovered proofs of occupation by Mousterian man in the very heart of the Alpine ice-fields of the Fourth Glacial Stage.] The upper waters of the Rhine and Danube were also frequented by late Acheulean and early Mousterian flint workers. At a point far distant from southern England there is the cavern of Wildkirchli on the Santis Mountains, near Appenzell, in Switzerland; in Mousterian times this was in the very heart of the north Alpine ice-field. The animal life here may indicate that this cavern was open during the period of recession between the two great advances of the fourth glaciation. Here, at a height of 4,500 feet, Bächler(19) between 1903-6, discovered proofs of occupation by Neanderthal man during Mousterian times; the flints are not well formed; the presence of crude bone implements may point to late Mousterian times; but the flints are considered by Bächler to be of the same stage as those of Le Moustier. It is asserted that when the Neanderthals followed the chase here the climate was more genial, because the animals found include the stag, Alpine wolf (_Cyon alpinus fossilis_), cave-bear, cave-lion, cave-leopard (_Felis pardus spelæa_), badger, marten, and otter, together with the typical Alpine forms, the ibex, chamois, and marmot. But this fauna alone can hardly be taken as proof of a temperate climate, for at this Alpine height we should not expect to discover the tundra life of the period; in fact, it is entirely absent.