16 DUTCH BORNEO-EXPEDITION. 



in the neighbourhood — must be considered as the remains 

 of an extremely large, old plateau of volcanic tuff, and 

 the valleys between as the work of the eroding power of 

 numerous roai'ing rivulets which form as many southern 

 tributaries of the Mandai River. 



One of these tributaries is the Raoen River, draining the 

 valley between the Liang Koeboeng-chaiu and the Tiloeng- 

 range. It falls into the Mandai River below Nanga Raoen, 

 and this latter name means, in fact, nothing but mouth 

 of the Raoen. About a mile above its mouth it receives 

 from the east the Siniai River, a small but very impetuous 

 torrent, which drains the narrow and very sharply cut 

 valley between the Liang Agang and the Liang Koeboeng- 

 chain. 



Being very anxious to get a chance to explore a region 

 in Dutch Borneo above the altitude of 1500 meter, I was 

 very much pleased to take the advice of Resident Tromp 

 and to choose for that purpose the Liang Koebang which, 

 according to his manuscript map of the Topographical 

 Survey, had a height of 1825 meter. After a few days' 

 stay at Nanga Raoen , and having secured two guides from 

 that place, I began the ascent of the Liang Koeboeng- 

 range. The ascent of the very steep flanks of the northern- 

 most top, the Ami Amit, with my voluminous outfit and a 

 large stock of provisions, proved to be extremely difficult, 

 no path whatever leading through the dense mountain 

 forest , which , hitherto , had been visited only by some Poe- 

 nans in search of rattan and dammar. It was only cutlass 

 in hand that our guides were able to open a narrow path 

 for the heavily ladeu carriers , and it was only after many 

 long hours of hard work that we reached the western foot 

 of the perpendicular rock-wall which flanks all round, at 

 an average height of 200 — 300 feet, the almost inacces- 

 sible top-platform of the mountain. 



The western slope of the mountain , the basis of the 

 huge bastion-like rocky plateau above us , was covered 

 with large boulders of rock , and roaring torrents , fed by 



Notes from tlie Leyden IMuseum, Vol. XIX. 



