406 D. A. Wray— 



But while the general outline is a down-like form, where the lime- 

 stone surfaces are quite devoid of any protective covering of 

 vegetation or red earth, very slight variations in rock-texture or 

 composition such as dolomitization, result in the production of a 

 highly fretted surface, known as grics or lapies. It is on the purest 

 limestones and where running water can operate on a great scale, 

 such as the bare regions of Herzegovina, to the north-east of the 

 Narenta, that the more typical grics are to be found. More usually 

 there are scattered patches of red earth covered with sage-bush, 

 alternating with bare patches, where a stunted vegetation flourishes 

 in clefts. Such regions have been described as esserts. 



PONORS AND DOLINAS. 



The funnel-shaped hollows which are so frequently met with on 

 the surface of the karst are termed ponors. Many of these are largely 

 filled with red earth, formed by the decomposition of the limestone, 

 and are then known as dolinas. The former Austrian maps of the 

 country to the east of Trieste indicate upwards of two hundred 

 ponors in an area of some 30 square miles, not including innumerable 

 minor hollows and dolinas. One of the largest is known as Katchna- 

 Jama, and is close to the village of Divatcha. It is over 1,500 feet 

 deep ; around it are no signs of faulting or movement, and it appears 

 to have originated along a major joint in the massive Cretaceous 

 limestone, and to have been enlarged solely by the action of running 

 water. 



The mode of origin of the lUyrian dolinas has given rise to con- 

 siderable discussion. Cvijic (2) many years ago pointed out that it 

 is only in exceptional cases where they originate through the collapse 

 of vaults of underground watercourses and grottoes. There is now 

 general agreement that in the first place they are due to the simple 

 penetration of meteoric waters localized by small fissures. An 

 important feature is the marked abundance of dolinas in such areas 

 as Southern Istria and the neighbourhood of Adelsberg, where there 

 is a fairly continuous covering of red earth, and a dense growth of low 

 vegetation, while they are comparatively infrequent on the bare 

 limestone surfaces. In the former cases the enlargement of the clefts 

 takes place more rapidly, presumably because of the greater erosive 

 power of water when charged with suspended matter, and also 

 (accordiag to Chaix-Du-Bois (9), who has studied the Adelsberg 

 district) probably because chemical erosion is powerfully augmented 

 where the vegetation is more intense. 



According to Grund (7), the greatest erosion probably takes place 

 inimediately above a uniform plane of saturation or water-table 

 at the base of the karst limestones. The continued uplift since 

 Miocene times has lowered this plane, with the result that with each 

 successive uplift vertical erosion has ensued, while with each 

 stationary period lateral erosion took place, resulting in the com- 

 plicated system of hollows that now stud the karstlands. Martel (4), 



