It is believed that the climate of Third Interglacial times when it reached its maximum warmth was again somewhat milder than the present climate in the same region. In the Alps the glaciers and the snow-line retreated once more to their present levels. The period opened with humid continental conditions. The areas left bare by the ice were gradually reforested. A picture of the climate in this warm period is presented in the region near Paris in the so-called _tuf de La Celle-sous-Moret_ (Seine-et-Marne). This tufa, which is a hot-springs deposit, overlies river-gravels of Pleistocene age.(7) The lower levels of the tufa contain the sycamore-maple (_Acer pseudoplatanus_), willows, and the Austrian pine, indicating a temperate climate. Higher up in the same deposits we find evidences of increasingly mild temperatures in the presence of the box (_Buxus_) and not infrequently of the fig-tree; the Canary laurel (_Laurus nobilis_) is somewhat rarer and both it and the fig indicate that the winters were mild, because these plants have the peculiarity of flowering during the winter season; we infer, therefore, that the climate was somewhat milder and more damp than it is in the same region at the present time. The mollusks also indicate greater equability of climate. These deposits are believed to correspond with the period of Chellean and early Acheulean industry. The plants in the highest levels of the same tufa, however, indicate the advent of a colder climate and also connect this with the Acheulean culture stage through the presence of Acheulean flints. The deposit of tufa is covered by a sheet of 'loess' corresponding with the return of an arid period in late Acheulean times, in the very heart of northern France. Thus we have a record in the region near the present city of Paris of three climatic phases, which are also more or less completely indicated in deposits to the north along the River Somme and in the valley of the ancient Thames. In western France we again interpret the fossil flora of Lorraine as belonging to the cooler closing period of Third Interglacial times and to the advent of the fourth glaciation, for here the most northern varieties of the larch (_Larix_) and of the mountain-pine (_Pinus lambertiana_) predominate.