as by numerous smaller rivers. Of the other three, which constitute
Dutch Borneo, the north-eastern is drained by the Batang Kayan or
Balungan river; the south-eastern by the Kotei and Banjermasin rivers;
and the south-western by the Kapuas, the largest of all the rivers,
whose course from the centre of the island to its south-west corner
is estimated at 700 miles. Although the point of intersection of the
two principal mountain chains lies almost exactly midway between the
northern and southern and the eastern and western extremities of the
island, the greater width of the southern half of the island gives a
longer course to the rivers of that part, in spite of the fact that
all the six principal rivers mentioned above have their sources not
far from this central point. The principal rivers thus radiate from
a common centre, the Batang Kayan flowing east-north-east, the Kotei
south-east by east, the Banjermasin south, the Kapuas a little south
of west, the Rejang west, and the Baram north-west. This radiation of
the rivers from a common centre is a fact of great importance for the
understanding of the ethnography of the island, since the rivers are
the great highways which movements of the population chiefly follow.

In almost all parts of the island, the land adjoining the coast is
a low-lying swampy belt consisting of the alluvium brought down by
the many rivers from the central highlands. This belt of alluvium
extends inland in many parts for fifty miles or more, and is especially
extensive in the south and south-east of the island.

Between the swampy coast belt and the mountains intervenes a zone of
very irregular hill country, of which the average height above the
sea-level is about one thousand feet, with occasional peaks rising
to five or six thousand feet or more.