Page:EB1911 - Volume 11.djvu/828

 Lakes.—The regions which abound in lakes have already been pointed out. The Lake of Constance or Bodensee (204 sq. m.) is on the frontier of the empire, portions of the northern banks belonging severally to Bavaria, Württemberg and Baden. In the south the largest lakes are the Chiemsee (33 sq. m.); the Ammersee and the Würmsee. A good many smaller lakes are to be found in the Bavarian Alps. The North German plain is dotted with upwards of 500 lakes, covering an area of about 2500 sq. m. The largest of these are the three Haffs—the Oder Haff covering 370 sq. m., the Frische Haff, 332, and the Kurische Haff, 626. The lakes in the Prussian and Pomeranian provinces, in Mecklenburg and in Holstein, and those of the Havel, have already been mentioned. In the west the only lakes of importance are the Steinhuder Meer, 14 m. north-west of Hanover, and the Dümmersee on the southern frontier of Oldenburg.

Geology.—Germany consists of a floor of folded Palaeozoic rocks upon which rest unconformably the comparatively little disturbed beds of the Mesozoic system, while in the North German plain a covering of modern deposits conceals the whole of the older strata from view, excepting some scattered and isolated outcrops of Cretaceous and Tertiary beds. The rocks which compose the ancient floor are thrown into folds which run approximately from W.S.W. to E.N.E. They are exposed on the one hand in the neighbourhood of the Rhine and on the other hand in the Bohemian massif. With the latter must be included the Frankenwald, the Thüringerwald, and even the Harz. The oldest rocks, belonging to the Archaean system, occur in the south, forming the Vosges and the Black Forest in the west, and the greater part of the Bohemian massif, including the Erzgebirge, in the east. They consist chiefly of gneiss and schist, with granite and other eruptive rocks. Farther north, in the Hunsrück, the Taunus, the Eifel and Westerwald, the Harz and the Frankenwald, the ancient floor is composed mainly of Devonian beds. Other Palaeozoic systems are, however, included in the folds. The Cambrian, for example, is exposed at Leimitz near Hof in the Frankenwald, and the important coal-field of the Saar lies on the southern side of the Hunsrück, while Ordovician and Silurian beds have been found in several localities. Along the northern border of the folded belt lies the coal basin of the Ruhr in Westphalia, which is the continuation of the Belgian coal-field, and bears much the same relation to the Rhenish Devonian area that the coal basin of Liége bears to the Ardennes. Carboniferous and Devonian beds are also found south-east of the Bohemian massif, where lies the extensive coal-field of Silesia. The Permian, as in England, is not involved in the folds which have affected the older beds, and in general lies unconformably upon them. It occurs chiefly around the masses of ancient rock, and one of the largest areas is that of the Saar.

Between the old rocks of the Rhine on the west and the ancient massif of Bohemia on the east a vast area of Triassic beds extends from Hanover to Basel and from Metz to Bayreuth. Over the greater part of this region the Triassic beds are free from folding and are nearly horizontal, but faulting is by no means absent, especially along the margins of the Bohemian and Rhenish hills. The Triassic beds must indeed have covered a large part of these old rock masses, but they have been preserved only where they were faulted down to a lower level. Along the southern margin of the Triassic area there is a long band of Jurassic beds dipping towards the Danube; and at its eastern extremity this band is continuous with a synclinal of Jurassic beds, running parallel to the western border of the Bohemian massif, but separated from it by a narrow strip of Triassic beds. Towards the north, in Hanover and Westphalia, the Triassic beds are followed by Jurassic and Cretaceous deposits, the latter being here the more important. As in the south of England, the lower beds of the Cretaceous are of estuarine origin and the Upper Cretaceous overlaps the Lower, lying in the valley of the Ruhr directly upon the Palaeozoic rocks. In Saxony also the upper Cretaceous beds rest directly upon the Palaeozoic or Archaean rocks. Still more to the east, in the province of Silesia, both Jurassic and Cretaceous beds are again met with, but they are to a large extent concealed by the recent accumulations of the great plain. The Eocene system is unknown in Germany except in the foothills of the Alps; but the Oligocene and Miocene are widely spread, especially in the great plain and in the depression of the Danube. The Oligocene is generally marine. Marine Miocene occurs in N.W. Germany and the Miocene of the Danube valley is also in part marine, but in central Germany it is of fluviatile or lacustrine origin. The lignites of Hesse, Cassel, &c., are interstratified with basaltic lava-flows which form the greater part of the Vogelsberg and other hills. The trachytes of the Siebengebirge are probably of slightly earlier date. The precise age of the volcanoes of the Eifel, many of which are in a very perfect state of preservation, is not clear, but they are certainly Tertiary or Post-tertiary. Leucite and nepheline lavas are here abundant. In the Siebengebirge the little crater of Roderberg, with its lavas and scoriae of leucite-basalt, is posterior to some of the Pleistocene river deposits.

A glance at a geological map of Germany will show that the greater part of Prussia and of German Poland is covered by Quaternary deposits. These are in part of glacial origin, and contain Scandinavian boulders; but fluviatile and aeolian deposits also occur. Quaternary beds also cover the floor of the broad depression through which the Rhine meanders from Basel to Mainz, and occupy a large part of the plain of the Danube. The depression of the Rhine is a trough lying between two faults or system of faults. The very much broader depression of the Danube is associated with the formation of the Alps, and was flooded by the sea during a part of the Miocene period.



Climate.—The climate of Germany is to be regarded as intermediate between the oceanic and continental climates of western and eastern Europe respectively. It has nothing in common with the Mediterranean climate of southern Europe, Germany being separated from that region by the lofty barrier of the Alps. Although there are very considerable differences in the range of temperature and the amount of rainfall throughout Germany, these are not so great as they would be were it not that the elevated plateaus and mountain chains are in the south, while the north is occupied by low-lying plains. In the west no chain of hills intercepts the warmer and moister winds which blow from the Atlantic, and these accordingly influence at times even the eastern regions of Germany. The mean annual temperature of south-western Germany, or the Rhine and Danube basins, is about 52° to 54° F., that of central Germany 48° to 50°, and that of the northern plain 46° to 48°. In Pomerania and West Prussia it is only 44° to 45°, and in East Prussia 42° to 44°. The mean January temperature varies between 22° and 34° (in Masuren and Cologne respectively); the mean July temperature, between 61° in north Schleswig and 68° at Cologne. The extremes of cold and heat are, as recorded in the ten years 1895–1905, 7° in Königsberg and 93° in Heidelberg (the hottest place in Germany). The difference in the mean annual temperature between the south-west and north-west of Germany amounts to about 3°. The contrasts of heat and cold are furnished by the valley of the Rhine above Mainz, which has the greatest mean heat, the mildest winter and the highest summer temperature, and the lake plateau of East Prussia, where Arys on the Spirdingsee has a like winter temperature to the Brocken at 3200 ft. The Baltic has the lowest spring temperature, and the autumn there is also not characterized by an appreciably higher degree of warmth. In central Germany the high plateaus of the Erz and Fichtelgebirge are the coldest regions. In south Germany the upper Bavarian plain experiences an inclement winter and a cold summer. In Alsace-Lorraine the Vosges and the plateau of Lorraine are also remarkable for low temperatures. The warmest districts of the German empire are the northern parts of the Rhine plain, from Karlsruhe downwards, especially the Rheintal; these are scarcely 300 ft. above the sea-level, and are protected by mountainous tracts of land. The same holds true of the valleys of the Neckar, Main and Mosel. Hence the vine is everywhere cultivated in these districts. The mean summer temperature there is 66° and upwards, while the average temperature of January does not descend to the freezing point (32°). The climate of north-western Germany (west of the Elbe) shows a predominating oceanic character, the summers not being too hot (mean summer temperature 60° to 62°), and snow in winter remaining but a short time on the ground. West of the Weser the average temperature of January exceeds 32°; to the east it sinks to 30°, and therefore the Elbe is generally covered with ice for some months of the year, as are also its tributaries. The farther