MINDANAO AND SULU : II. PHYSIOGRAPHY. 



351 



narrow strip of moderately elevated 

 Pulangui, flowing northwest in a 

 valley with long, gentle slopes up 

 to Mount Katunlud on the west, 

 but with very rugged hills on the 

 east. In the upper part of its 

 course its tributaries join it, mak- 

 ing an acute angle upstream in 

 the normal way, but below the 

 confluence of the Manguina and 

 the Tagoloan Eivers the latter 

 enters a narrow gorge with only 

 one side stream coming in from 

 the west in a distance of 19 kilo- 

 meters, but with 24 entering from 

 the east and all of these approxi- 

 mately at right angles. ( See Plate 

 III.) This remarkable drainage 

 arrangement must be due to fault- 

 ing and joining. There undoubt- 

 edly was a local uplift east and 

 west across the courses of these 

 rivers, after they had become well 

 established. The country to the 

 south of their headwaters be- 

 comes more open and flat. 



(4) The Tumaga River is very 

 small and scarcely navigable above 

 1| kilometers from its mouth. It 

 is mentioned here because of 

 its importance to Zamboanga as 

 a source of potable water. It is 

 not much over 32 kilometers in 

 length and very narrow and 

 shallow. It rises on the slopes of 

 Mount Panubigan, flows about due 

 south over schists and along their 

 strike until it issues from the 

 Zamboanga gorge onto the plain, 

 where after a short distance it 

 turns sharply to the east. Just 

 what has so sharply deflected this 

 stream is not apparent, unless, 

 perchance, during a freshet it de- 

 posited on the plain near Zam- 



country from the headwaters of the 



