BORNEO 227 
fifty miles, and trading praus ascend it for an immense 
distance. 
The Mahakkam, like all the great rivers of Borneo, 
rises in the unexplored regions of Mount Tebang, and 
follows a south-east course for over 400 miles, to pour its 
waters into the Strait of Makassar. It receives numerous 
tributaries, and exhibits in a marked degree the phe¬ 
nomenon of lake expansion. The permanent lakes in its 
course are filling up gradually, but they are still of con¬ 
siderable depth, for Mr. Carl Bock, who lately travelled in 
this region, speaks of getting soundings of 8 0 feet or more. 
The Mahakkam has the large town of Samarinda at its 
mouth, and forms, like the Kapuas, a very considerable 
delta. Farther north, the rivers in Dutch territory are 
little known. The most important waterway in British 
North Borneo is the Kinabatangan, which debouches be¬ 
tween Darvel and Sandakan Bays, and is navigable by 
boats for about 200 miles. 
Certain marked characteristics, then, are exhibited by 
the majority of Bornean rivers, but more especially by 
those of the southern and eastern portions of the island, 
and these peculiarities are determined to a great extent 
by the flatness and slight elevation of the surrounding 
land. Most are surrounded in the lower part of their 
course with a greater or less extent of impassable morass. 
In most cases deltas are formed, sometimes of very large 
size, and here, aided by the mangroves, the land gains 
very rapidly on the sea. The slight fall in the river 
beds causes daily tidal inundation, and periodic flooding 
of vast areas occurs in the rainy season. For like 
reasons the rivers are extremely serpentine in their 
course, and in flood time the intervening land is often 
cut across at the narrow part of the bend. The old bed 
becomes partially blocked, and the phenomenon is thus 
