DRAINAGE OF THE SINGU-TANGYI HILLS. £$ 



Sandstones and shales which resist weathering unequally. On the east 

 side of the anticlinal arch, where the beds are dipping at high angles, 

 the hills take the form of a number of narrow parallel ridges, but oa 

 the west side of the anticline, where they have only gentle dips, the 

 ridges have a dip slope on the west side and a steep scarp facing 

 towards the east. The pliocene area, as a rule, rises more gradually 

 from the surrounding country and tends to form broad plateaux, 

 which are, however, cut into by innumerable stream-beds. 



Very numerous stream-beds drain the Singu-Tangyi hills, with 

 courses both to the east and to the west, but the watershed 

 is not at the crest of the anticlinal fold ; in the Singu hills it is 

 the ridge of pliocene beds on the eastern side of the arch, and in 

 the Tangyi hills it is the ridges of miocene beds about half-way 

 between the crests of the fold and their western boundary. In 

 the hills the general course of the main streams is at right angles to 

 the axis of the anticline and the strike of the beds, and here, 

 flowing over the miocene rocks, the tributary streams largely run 

 along the strike, but in the pliocene hills they radiate in all direc- 

 tions. Many of the larger streams have cut deep nullahs and valleys 

 in the hills, which often have lofty and precipitous sides ; but in some 

 places, especially amongst the pliocene hills and where aided by 

 numerous tributary streams, they have worn out broad valleys and 

 deposited alluvium in them. Most of these stream beds were quite 

 dry during the whole of the time, November to April, which I spent 

 in the country, and in no case was the water flowing into the 

 Irrawaddi. The only exceptions to the rule of being perfectly 

 dry in the cold and hot seasons were a few stream-beds in the Tangyi 

 hills, where the nullahs have been cut through miocene beds, 

 in which small pools are found in places, and the water sometimes 

 flows for a short distance before sinking again underneath the sands, 

 but in no case does the water flow on the surface of the ground into 

 the Irrawaddi. 



The Yaw-Chaung, which flows along the base of the Tangyi 

 D ( 33 ) 



