The temperature with great extremes, in summer up to 120° F. and in winter below 20° F., was the characteristic of this climate; the atmosphere was very dry in the hot season, but in the rest of the year there was some humidity in the air and moisture in the soil, the water of the subsoil being not very deep. The atmospheric precipitation in this region was caused by the south-west wind just as at present; but the dominant wind giving the character of a dry continental climate was the north-east wind (Crivat) which has left its traces in the fossil dunes of the Baragan.” A history of the changes of climate in Europe which followed the maximum of the last readvance of the ice-sheet must be left to later chapters. BIBLIOGRAPHY Brooks, C. E. P. “The correlation of the Quaternary deposits of the British Isles with those of the continent of Europe.” _Ann. Rep. Smithsonian Inst._, 1917, pp. 277-375. [Full list of references.] Penck, A., and Brückner, E. “Die Alpen in Eiszeitalter.” 3 Vols. _Leipzig_, 1901-9. Gagel, C. “Die Beweise für eine mehrfache Vereisung Norddeutschlands in diluvialer Zeit.” _Geol. Rundschau_, 4, 1913, p. 39. Wahnschaffe, F. “Die Oberflächengestaltung des norddeutschen Flachlandes.” Stuttgart, 1910. Svastos, R. “Le postglaciare dans l’Europe centrale du nord et orientale.” _Ann. Sci. Univ. Jassy_, 4, 1908, p. 48. CHAPTER VI THE MEDITERRANEAN REGIONS DURING THE GLACIAL PERIOD Our knowledge of the history of the Mediterranean basin during the Glacial period is not nearly so complete as is that of the more northern regions, chiefly for the reason that during most of the period the land lay above its present level, and except for local glaciers in the mountain regions there was no ice to leave us a record of the changing climates. Most of what we do know relates to the relatively brief periods of submergence. At the beginning of the Glacial period the sea lay some 500 feet above its present level, and we can trace the first appearance of a northern marine fauna. This stage is known as the Calabrian; it is divided into two horizons—a lower, in which northern forms are still rare, and an upper, in which they are becoming abundant. The most typical species are two mollusca whose present habitat is the coast of Iceland—_Chlamys (Pecten) islandicus_ and _Cyprina islandica_. The Calabrian beach is not found on the coast of Spain or at Gibraltar, and in Algeria it probably occurs at a lower level. This suggests that the subsidence at this period was local, and the western lands stood up as a barrier against the Atlantic. There must have been a channel of some sort, however, on the site of the present Straits of Gibraltar, to provide an inlet for the immigrating northern mollusca. In the Maritime Alps, and again in the eastern Mediterranean, the Calabrian beaches are at a much greater height owing to local elevation.