The Upper. Kapoewas, the Boengan, the Boelit, and the boundary mountains between West and East Borneo 1 ).

The mountain-land of the Upper Kapoewas is very thinly populated and exclusively by nomadic Poenan tribes frequenting the forests. The nomadic Dyaks in the Upper Kapoewas district are generally called Boekats, while more towards the east, in the boundary mountains of East Borneo, their collective name is Poenans. The houses on the right shore of the Kapoewas, Poetoes Sibau are all fortified as a defence against the Batang Loepars of Sarawak, who until quite lately extended their head-hunting expeditions as far as the Upper Kapoewas. The Kapoewas itself meanders greatly in its upper course, and for long distances forms longitudinal valleys running from east to west, which are connected by short transverse valleys running north and south. The development in length of the stream therefore is very great. The source of the Kapoewas is only 19 kilometres from pangkalan Djemoeki, as the crow flies, but the actual length of the river between those two points is 49 kilometres.