224 
COMPENDIUM OF GEOGEAPHY AND TEAYEL 
that it is often possible to pass from one river-basin to 
another without any great ascent, and this arrangement 
of the mountains may be regarded as a characteristic 
feature of the orography of the island. 
Borneo is remarkable both for its plains and rivers. 
The southern and eastern portions of the island are, in 
the main, areas of flatness and little elevation, as may be 
gathered from a glance at the map, which shows the 
rivers to be of almost phenomenal tortuousness. In some 
places quite flat, in others gently undulating, these plains 
occupy the spot where, in pre-Tertiary days, the sea 
flowed. Towards the coast, and in the vicinity of rivers, 
this flat land often exists as vast and impassable 
morasses, which in the wet season become much en¬ 
larged, so that enormous areas become submerged. 
Schwaner estimated that 160 square geographical miles 
are daily flooded by tidal action in the basin of the 
Barito, and 580—or more than one-third of the entire 
basin—in the rainy season. Like phenomena may be 
witnessed upon many, if not most, other of these rivers, 
and Dr. Posewitz, in his work on the geology of the 
island, gives the following graphic description of the 
appearance of the district surrounding the Negara, an 
affluent of the Barito. “ During my first journey every¬ 
thing, as far as the eye could see, was covered with water : 
it appeared to extend to the mountain-chain skirting the 
eastern horizon, the foot of which is surrounded by steep 
Tertiary coral reefs. In the midst of the flooded district 
one could see Negara, an important seat of industry, extend¬ 
ing along the end of the great sheet of water, as if it were 
situated on an inland sea. In the swampy parts there 
were thick patches of rushes, which formed welcome 
resting-places for dense swarms of mosquitoes, and the 
oarsman in threading his way is obliged to keep a sharp 
