The Karst or Carso formation on which Slovene life developed is the western section of a long calcareous plateau which extends from the Julian Alps, along the border of the ancient Friulian gulf and attains Balkan ranges. It separates the valley of the Save from the Adriatic. A characteristic aspect is noticeable over all its extent in the thickness of its limestone beds and their deep fissures. Surface water cannot collect and flow for any distance without disappearing into a fissure. The erosion forms of the plateau are of the Karst type and differ radically from those of the average humid climate. Chambers of marvelous dimensions are formed; funnel-shaped sink-holes dot the surface; and the rivers run underground. The Slovenes settled on the calcareous plateau of Carniola cluster around Laibach and attain the area of German speech on the north, along the Drave between Marburg and Klagenfurth. Eastward they march with Hungarians and the Serbo-Croat group of southern Slavs. Their southern linguistic boundary also coincides with that of the latter. Around Gottschee, however, a zone of German intervenes between Slovene and Croatian dialects. Practically the entire eastern coast of the Gulf of Triest lies in the area of Slovene speech. The group thereby acquires the advantage of direct access to the sea, a fact of no mean importance among the causes that contributed to its survival to the present day in spite of its being surrounded by Germans, Hungarians, Croats and Italians. The Slovenes may be considered as laggards among the Slavic immigrants who followed Avar invasions. They would probably have occupied the fertile plains of Hungary had they not been driven to their elevated home by the pressure of Magyar and Turkish advances. Confinement in the upland prevented their fusion with any of the successive occupants of the eastern plains below their mountain habitations. Racial distinctiveness, characterized by language no less than by a highly developed attachment to tradition, resulted from this seclusion.