402 B. A. Wray— 



Dinaric (N.W.-S.E.) trend. The more easterly group includes those 

 of Grahovo, Njegus, Cettinje, and Ljubotin. West of these occur 

 the poljes of Nitchitchi, Danilovgrad, and Podgoritsa. 



All the Bosnian poljes are considered by Katzer (10) to have 

 originated with the Miocene orogenic movements, and to be bordered 

 by longitudinal fractures. Cvijic (3), on the other hand, maintains 

 that every gradation exists between the minor erosion hollows of the 

 karst and the poljes ; the remarkably rectilinear form of the latter 

 being due to the prevailing strike of the limestones. 



All the Bosnian poljes agree in possessing remarkably straight and 

 almost precipitous walls surrounding a flat featureless depression, 

 and are largely basins of internal drainage. The largest polje of the 

 Western Balkans is that of Livno, which extends in a N.W.-S.E. 

 direction for over 40 miles and is from 3 to 7 miles in width. Its 

 walls consist mainly of Cretaceous limestones, and to the north-west 

 include Triassic and Jurassic limestones, while it is floored with 

 Upper Oligocene or Lower Miocene freshwater limestones and marls, 

 with beds of lignite up to 10 feet in thickness. The drainage of the 

 polje is towards the centre, streams flowing from the north-west, 

 eventually disappearing in deep swallow holes, termed " ponors ", 

 while those draining in from the south-eastern end around Livno 

 also eventually disappear in ponors below the surface. The Livno 

 polje has two subterranean outlets, which each pass by means of east 

 and west courses under the Dinaric range to the west into the Cetina 

 valley and eventually enter the sea opposite the island of Brazza. 

 Each of these underground channels following the line of the major 

 joints in the Cretaceous limestones is upwards of 8 miles long. The 

 more northern disappears in the ground to the immediate north of 

 Bujani, and emerges close to the village of Hrvace, in the Cetina 

 valley, while the more southern one enters the Sinjsko polje at the 

 village of Otok. Li wet seasons these channels are unable to take 

 the whole of the drainage of the basin and for upwards of seven 

 months of the year the Livansko polje forms an inland sea or marsh. 

 The floor of the polje forms, however, the only fertile region in the. 

 district ; consequently within the past few years efforts have been 

 m.ade to drain it by means of irrigation. The Glamoc, Kupres, and 

 Duvno poljes are similar in almost every respect to that of Livno. 



The Nevesinje polje, which is 15 miles long and has an 

 average width of 5 miles, is in Central Herzegovina, to the east of 

 Mostar. That of Gacko, which has an area of 30 square miles, lies 

 to the east of Nevesinje, and close to the Montenegrin borders. The 

 floor of the polje, consisting of lignite-bearing Miocene con- 

 glomerates, marls, and freshwater limestones, is just over 3,000 feet 

 above sea-level, and is abruptly hemmed in by the Bjelasitsa and 

 Lebrsnik ranges of massive limestone, which each attain over 6,000 feet 

 above the level of the sea. Li the Gacko polje the mountain streams, 

 which formerly converted it into a marsh for the major portion of the 

 year, have been dammed, collected in large storage reservoirs, and 



