These chains are: (1) the folded chain of the upper Kapuas, which divides the western division of Dutch Borneo from Sarawak, extends west to east, and attains near the sources of the Kapuas river a height of s000 to 6000 ft.; (2) the Schwaner chain, south of the Kapuas, whose summits range from 3000 to 7500 ft., the latter being the height of Bukit Raja, a plateau which divides the waters of the Kapuas from the rivers of southern Borneo; and (3) the Muller chain, between the eastern parts of the Madi plateau (presently to be mentioned) and the Kapuas chain, a volcanic region presenting heights, such as Bukit Terata (4700 ft.), which were once active but are now long extinct volcanos.
The Madi plateau lies between the Kapuas and the Schwaner chains.
From the eastern end of the Kapuas mountains there are further to be observed: (1) A chain running north-north-east, which forms the boundary between Sarawak and Dutch Borneo, the highest peak of which, Gunong Tebang, approaches io,000 ft.
Of these the shortest embraces the north-western slope, north of the Kapuas range, and discharges its waters into the China Sea.
In the south-western versant the largest river is the Kapuas, which, rising near the centre of the island, falls into the sea between Mampawa and Sukadana after a long and winding course.
The Sambas, north of the Kapuas, is navigable in its lower course for vessels drawing 25 ft.
Rivers lying to the south of the Kapuas, but of less importance in the way of size, commerce and navigation, are the Simpang, Pawan and Kandawangan, in the neighbourhood of whose mouths, or upon the adjacent coast, the principal native villages are situated in each case.
Cross branches unite it with two rivers of considerable size towards the west, the Kapuas Murung or Little Dyak, and the Kahayan or Great Dyak.
At a great distance from its mouth it has still a depth of three fathoms, and in all its physical features it is comparable to the Kapuas and Barito.
In the flood area of the upper Kapuas, of which mention has already been made, there occurs Lake Luar, and there are several lake expanses of a similar character in the basins of the Barito and Kutei rivers.
The Kapuas valley has so far yielded the largest quantity, and Pontianak is, for diamonds, the principal port of export.