The Pagan Tribes of Borneo | Page 9

these two principal mountain chains which determine
the main features of the river-system, there are several isolated peaks of
considerable height, and a minor ridge of hills runs from the centre
towards the south-cast corner. With the exception of the northern
extremity, which geographically as well as politically stands apart from
the rest of the island, the whole of Borneo may be described as divided
by the two principal mountain chains into four large watersheds. Of
these, the north-western basin, the territory of Sarawak, is drained by
the Rejang and Baram, as well 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.
There seems good reason to believe that at a comparatively recent date
Borneo was continuous with the mainland of Asia, forming its
south-eastern extremity. Together with Sumatra and Java it stands upon
a submarine bank, which is nowhere more than one hundred fathoms
below the surface, but which plunges down to a much greater depth
along a line a little east of Borneo (Wallace's line). The abundance of
volcanic activity in the archipelago marks it as a part of the earth's crust
liable to changes of elevation, and the accumulation of volcanic matter
would tend to make it an area of subsidence; while the north-east
monsoon, which blows with considerable violence down the China Sea
for about four months of each year, may have hastened the separation
of Borneo from the mainland. That this separation was effected in a
very recent geological period is shown by the presence in Borneo of
many species of Asiatic mammals both large and small, notably the
rhinoceros (R. BORNIENSIS, closely allied to R. SUMATRANUS);
the elephant (E. INDICUS, which, however, may have been imported
by man); the wild cattle (BOS SONDIACUS, which occurs also in
Sumatra); several species of deer and pig (some of which are found in
Sumatra and the mainland); several species of the cat tribe, of which
the tiger-cat (FELIS NEBULOSA) is the largest; the civet-cat
(VIVERRA) and its congeners HEMIGALE, PARADOXURUS, and
ARCTOGALE; the small black bear (URSUS MALAYANUS); the
clawless otter (LUTRA CINEREA); the bear-cat (ARCTICTIS
BINTURONG); the scaly ant-eater (MANIS JAVANICUS); the lemurs
(TARSIUS SPECTRUM and NYCTICEBUS TARDIGRADUS); the
flying lemur (GALEOPITHECUS VOLANS); the porcupine
(HYSTRIX CRASSISPINIS); numerous bats, squirrels, rats and mice;
the big shrew (GYMNURA); several species of monkeys, and two of

the anthropoid apes. The last are of peculiar significance, since they are
incapable of crossing even narrow channels of water, and must be
regarded as products of a very late stage of biological evolution. Of
these two anthropoid species, the gibbon (HYLOBATES MULLERI) is
closely allied to species found in the mainland and in Sumatra, while
the MAIAS or orang-utan (SIMIA SALYRUS) is found also in
Sumatra and, though not now surviving on the continent, must be
regarded as related to anthropoids whose fossil remains have been
discovered there.[2]
The zoological evidence thus indicates a recent separation of Borneo
and Sumatra from the continent, and a still more recent separation
between the two islands.
The climate of the whole