On the southeast Kara Bay penetrates deeply into the mainland, and to the west of this the short Kara river enters the sea.
Another place which proved attractive to colonists of that race was the curious narrow strip of ground, called the Thracian Chersonese, that intervened between the Hellespont and the Bay of Melas, which penetrates far into the land on its northern side.
It still flows on, however, as a deep current and it then becomes a factor of immense importance with regard to the fisheries in the regions into which it penetrates.
Rising amid the ancient gneiss rocks of the St Gotthard, the Rhine finds its way down to the Lake of Constance between layers of Triassic and Jurassic formation; and between that lake and Basel it penetrates the chalk barrier of the Jura.
Moreover the rain penetrates into the small interstices between its particles and dissolves out some of the materials which bind the whole into a solid stone, the surface then becoming a loose powdery mass which falls to the ground below or is carried away by the wind.
