This region, so tiresome to the eye, is yet interesting to the student of the pre-historic condition of this vast flat region. Covered everywhere with a deep layer of drifted materials, which consist, for the most part, of sand, sometimes of gravel, and more rarely of clay, no rocks are seen _in situ_ for thousands of square miles. But strewed, now on the surface, now at depths of two or three feet, and now beneath fifty or sixty feet of sand or gravel, lie countless blocks of foreign stone, of every size, from that of the fort to that of a small house. These the waters of the once larger Baltic brought down ages ago from the rocky cliffs of the Finnish and Bothnian gulfs. During that very recent geological epoch which immediately preceded the occupation of the country by living races, these flats of North Germany, as far south and east as the mountains of Silesia, were covered by the waters of the Baltic Sea. Yearly over this sea the northern ice drifted, bearing with it blocks of granite and other old rocks as it floated southward, dropping masses here and there by the way as the ice-ships melted before the summer sun. But in greater numbers they bore them to the shores on which the ice floes stranded and strewed them in heaps along the flanks of the Silesian hills. Hence now, when the land has risen above the sea, the huge stones so transported, age after age, are found at every step, if not on the very surface, yet always at some small depth beneath the sand, or gravel, or clay, or in the deep peat which covers so much of the wide area. And, piled up in heaps on the slopes of the Silesian mountains, at heights of nine hundred to twelve hundred feet, the traveller wonders to see the same distant-borne strangers, unlike any of the living rocks on which they rest, and which talk intelligibly to the geologist of their ancient homes in the frozen wilds of Scandinavia.