Upon the steeper slopes over the purer limestones, the rain water runs away, guided by the joints within the rock. There is thus etched out a more or less complete network of narrow channels (Fig. 190, p. 181), between which the remnants rise in sharp blades to produce a structure often simulated upon the fissured surface of a glacier that has been melted in the sun’s rays (Fig. 401). These almost impassable areas of karst country are described as _Schratten_ or _Karrenfelder_ (Fig. 198). =The ponore and the polje.=—To-day large areas of the Karst are devoid of surface streams, nearly all the surface water finding its way down the crevices of the limestone into caverns, and there flowing in subterranean courses. The foot traveler in the Karst country is sometimes suddenly arrested to find a precipice yawning at his feet, and looking down a well-like opening to the depth of a hundred feet or more, he may see at the bottom a large river which emerges from beneath the one wall to disappear beneath the other. These well-like shafts are in the Austrian Karst known as _Ponores_, while to the southward in Greece they are called _Katavothren_. ┌──────────────────────────────────────────────────────────────────────┐ │ PLATE 6. │ │ │ │ [Illustration: _A._ Barren Karst landscape near the famous Adelsberg │ │ grottoes. │ │ (_Photograph by I. D. Scott._)] │ │ │ │ [Illustration: _B._ Surface of a limestone ledge where joints have │ │ been widened through solution. │ │ Syracuse, N.Y. │ │ (_Photograph by I. D. Scott._)] │ └──────────────────────────────────────────────────────────────────────┘