18 LA TOUCHE: GEOLOGY OF NORTHERN SHAN STATES. 



that of the tributary, seem to suggest that the original drainage of 

 the plateau was more complex than it is at present, and that the 

 courses of these rivers were in former times more independent of 

 each other. The present Nam-Tu seems to be the result of a 

 ' cutting-back ' of one river, which has gradually invaded the 

 valleys of the other streams, and turned them into its own channel. 

 This action was no doubt aided by the numerous dislocations 

 affecting the mass of limestone forming the plateau, of which there 

 appear to be two systems, more or less at right angles to each 

 other. If this view is correct, the Nam-Tu, as we find 

 it at present, is as a whole of later date than some of its 

 tributaries. The original courses of these tributaries cannot now 

 be detected, owing to the peculiar nature, to be described below, 

 of the denudation that the limestone of the plateau has under- 

 gone. 1 



The ' cutting back ' action of the streams along the edge of the 

 , plateau, is well shown in the case of that 



Sedaw gorge. . . 



which issues from the western scarp at Sedaw 

 (B 5), where the railway begins the ascent to Maymyo by a 

 series of zig-zags. This gorge extends eastwards parallel to the 

 railway to within a few miles of Maymyo, and for the greater part 

 of its length is of great depth, flanked on either side by perpendi- 

 cular cliffs of limestone. At the head of the gorge the cliffs draw 

 together, forming a roughly defined cirque, over which the stream 

 plunges in a cataract several hundred feet high. Above this the 

 valley is open, and the stream sluggish. Its source is in the hills 

 north of Maymyo, which lies on the watershed between this stream 

 and the Ke-laung, a tributary of the Nam-Tu. Should the cutting 

 back action at the head of this gorge continue, it will in time 

 capture part of the area drained by the Ke-laung, and if the latter 



1 Perhaps the comparatively recent origin of the course of the Nam-Tu may be the 

 source of a legend current among the Palaungs, a people inhabiting the hilly country of 

 Tawng-peng. According to this, the river was brought into existence by a Chinese 

 Princess named Nang Hkam Long, possessed of miraculous powers, who visited the Shan 

 States on a raft which she could cause to travel in any direction she pleased, by pro- 

 ducing water in front of it. Coming to Loi Hpra, a hill in Tawng-peng, she wished 

 the Sawbwa, or chief of the State, to marry her ; but was rejected by him on the plea 

 that ' her bosom indicated old age,' and that he already possessed too many wives. 

 Repulsed by him, she proceeded to Hsipaw, where, she was apparently entertained 

 more hospitably, and thence to Ava ; and the Nam-Tu marks the course of her 

 journey. The Palaungs believe that if their Sawbwa had not beon so ungallant, the 

 river would have rim bv Loi Hpra, and that their country would not be so mountain 

 ous (J. (J. Scott, Gazetteer of Upper Burma and the Shan States Part I. Vol. 

 p. -188) 



