4 COGGIN BROWN : MINES & MINERAL RESOURCES OF YUNNAN. 



ranges, the river itself being nearer 2,000 feet. The ranges between 

 the Irrawaddy river and the frontier are held to belong to the Hima- 

 layan system as distinct from the Mekong chains. 



The parallel courses of the Salween, Mekong and Yangtze, 



flowing to the south-south-east through Yunnanes'e Tibet form 



one of the most remarkable geographical features of the earth's 



surface. £i Each of these rivers drains a large area of Eastern Tibet 



and on the surface of the plateau they flow at considerable distances 



from one another. But during their descent they bend to the 



east-south-east, and assume absolutely parallel courses, the Mekong 



in the centre being 28 miles from the Yangtze and 20 miles from 



the Salween " (Burrard and Hayden : The Geography and Geology of 



tfte Himalaya Mountains and Tibet, p. 127). The parallel arrangement 



of their courses extends across more than 2 degrees of latitude. The 



direction of their flow is along well-known tectonic lines, and the 



profound depths of their canons is due to late Tertiary or Subrecent 



uplifts on a grand scale, evidences of which are found throughout 



the province. 



Central Yunnan, extending say from the Mekong valley to the 

 region of the lakes, has been referred to by most writers as a plateau. 

 It is difficult to understand how such a misconception has arisen 

 as this portion is occupied by the western limb and central portion 

 of the Yunnanese arc. Between the Mekong and the Red River 

 the direction of the mountain ranges is north-west and south-east, 

 between the Red River and the lakes a rapid change of direction 

 takes place to approximately east and west, while further on in 

 north-eastern Yunnan high mountain chains stretch far to the 

 north-north-east and form the eastern limb of the Yunnanese arc. 

 The central portion of the arc is thus narrow and compressed ; it 

 does not extend much below lat. 23° 30', and the mountain ranges 

 of the southern part of central Yumian below this line belong to 

 the Indo-Chinese system. 



A little to the south of the 27th parallel and close to the 100th 

 meridian, the Yangtze abruptly changes its course which has up 

 to this point followed the same direction as those of the Mekong 

 and Salween, and after making its well-known bend commences 

 to flow to the east. No satisfactory reason was apparent for this 

 until Deprat pointed out how it depends on the direction of the 

 main lines of folding as apparent in the mountain ranges. " If 

 the Salween, Mekong and Upper Yangtze flow in parallel directions 



