ampart of
limestone. These _poljes_ may be described as oases in what is otherwise
a desert expanse of mountains. The surface of some, as notably the
_Mostarsko Blato_, lying west of Mostar, is marshy, and in spring forms
a lake; others are watered by streams which disappear in swallow-holes
of the rock, and make their way by underground channels either to the
sea or the Narenta. The most conspicuous example of these is the
Trebinjcica, which disappears in two swallow-holes in Popovopolye, and
after making its way by a subterranean passage through a range of
mountains, wells up in the mighty source of Ombla near Ragusa, and
hurries in undiminished volume to the Adriatic. The Narenta, or Neretva,
is the one large river of Herzegovina which flows above ground
throughout its length. Rising on the Montenegrin border, under the
Lebrsnik mountains, it flows north-westwards at the foot of the Dinaric
Alps; and, near Konjica, sweeps round suddenly to the south, and falls
into the Adriatic near Metkovic, after traversing 125 m. North of
Mostar, it cleaves a passage through the celebrated Narenta defile, a
narrow gorge, 12 m. long, overshadowed by mountains which rise on either
side and culminate in Lupoglav (6796 ft.) on the east, and Cvrstnica
(7205 ft.) on the west.

2. _Geology and Minerals._--Geologically, the highlands of Bosnia and
Herzegovina are to be regarded, in both their orographic and tectonic
character, as a continuation of the South Alpine calcareous belt. Along
the west frontier there appear broad and strongly marked zones of
Cretaceous limestone, alternating with Jurassic and Triassic, joined by
a strip of Palaeozoic formations running from the north-west corner of
Bosnia. Next, proceeding from this region in an easterly direction, are
the Neogene freshwater formations, filling up the greatest part of the
north-east of Bosnia, as also a zone of flysch intermingled with several
strips of eruptive rock. In the south-east of Bosnia the predominant
formations are Triassic and Palaeozoic strata with red sandstone and
quartzite. Along the whole northern rim of Bosnia, as also in the
fluvial and Karst valleys (_poljes_), are found diluvial and alluvial
formations, interrupted at one place by an isolated granite layer.
Bosnia is rich in minerals, including coal, iron, copper, chrome,
manganese, cinnabar, zinc and mercury, besides marble and much excellent
building stone. Among the mountains, gold and silver were worked