INTRODUCTORY ESSAY. 315 



laya, the rain-fall is much greater at the eastern extremity of 

 the chain than it is to the westward. Hence Western Tibet 

 is considerably drier than Eastern Tibet ; indeed, the lower 

 part of the course of the Indus, where that river enters the 

 Panjab plain, is situated in a rainless climate ; but the lower 

 part of the course of the Yarn, where under the name of the 

 Dihong it joins the Brahmaputra, lies in one of the raiaiest 

 climates of the globe. 



The chain of the Kouenlun, where it forms the northern 

 boundary of Western Tibet, is not less elevated than the Hi- 

 malaya, and is covered throughout a great part of its length 

 with perpetual snow. Its axis has not been crossed by any 

 European traveller, but has been reached by Dr. Thomson, 

 who visited the Karakoram Pass, elevated 18,300 feet. This 

 chain has been called the Mus-tagh, Karakoram, Hindu Kush, 

 and Tsungling or Onion mountains (from the prevalence of a 

 species of Allium) ; it is also the Belur-tagh,* which (accord- 

 ing to Cunningham) is synonymous with " Balti mountains," 

 and its continuation forms the Pamir range west of Yarkand. 

 In Western Tibet, the axis of this chain is in general distant 

 about 150 miles from the Himalaya, and the country between 

 the two consists of a complication of ranges of lofty and rugged 

 mountains, separated from one another by stony vaUeys, which 

 on the higher parts of the courses of the rivers expand at in- 

 tervals into alluvial plains. 



The Indus, near its source, has an elevation of 18,000 feet, 

 and where it debouches on the plains of the Panjab it is ele- 

 vated only 1000 feet. At Le it is 10,500 feet, and at Iskardo 

 7200 feet. Below 10,000 feet, the summer heat, from the ab- 

 sence of rain, is intense, and the Tibetan flora becomes more 

 Sindian and Persian in character. West of Kashmir and the 

 great peak of Dayamar, the Himalaya diminishes rapidly in 

 elevation, and allows access to the humid atmosphere, which 

 is condensed on the first ranges of Tibet with which it comes 



* The Bulut-Tag (or Cloud Mountains) of Captain H. Strachey, who confinca 

 the term to the range east of Samarkand and south of Khokand. 



