CAENIOLA, CROATIA, SLAVONIA. 



67 



form temporary lakes. One of these lakes, formed by the Gaika near Oto6ac, 

 sometimes attains a depth of no less than 160 feet. 



The Piuka, which is swallowed up by the caverns of Postoina, or Adelsberg 

 (Arse Posthumii), so rich in stalactites, is perhaps quite as remarkable a river as 

 the Timavo. After an underground course of about 6 miles the Piuka once 

 more reaches the surface, a calm and powerful river. Soon after its junction with 

 the Unz it is again swallowed up, and only reappears a short distance above 

 Laibach. 



Amongst the rivers which discharge themselves into the Unz is the effluent of 



Fig. 42. — The Lake of Zirknitz. 



Scale 1 : 115,000. 



2 Miles. 



the famous Lake of Zirknitz. In the dry season its water is drained off through 

 the numerous fissures and caverns which perforate its bed. After rains it rises to 

 the surface, sometimes very suddenly, and occasionally the lake spreads over a 

 surface of 30 square miles. Drainage works have to some extent regulated 

 the ebb and flow of the lake. In former times, however, the whole of the plain 

 was occasionally converted into a lake, and the villagers alternately gained a 

 livelihood by fishing and by tilling the land when it emerged. 



The plain of Laibach, 66 square miles in extent, was formerly occupied by 

 a lake similar to that of Zirknitz, fed by the Unz, and from numerous sinks, 

 locally known as " windows." Weeks passed sometimes before the waters were 



