216 ' FLORA INDICA. 



in contact. The Tibetan Flora of the Indus, therefore, ends a 

 little below Iskardo, pines appearing in the district of Rondu, 



and throughout the valley of Hasora, which latter may hence 

 be regarded as not Tibetan. 



The mean elevation of Western Tibet exceeds that of all 

 countries of which we have any definite knowledge, and, if 

 not surpassed by part of Eastern Tibet, is without doubt the 

 loftiest area of any considerable extent on the surface of the 

 globe. Captain H. Strachey gives 15,000 feet as the approxi- 

 mate mean elevation ; and when we consider that there are 

 throughout Tibet many ranges of a uniform elevation of 19- 

 20,000 feet, and peaks innumerable of 21-25,000, as also that 

 the very lowest level of the Indus valley (itself a mere cleft in 

 the mountain mass) is 6000 feet, the above estimate will not 

 be considered exaggerated. Of the passes over the main axis of 

 the Kouenlun and Himalaya, and over their principal ramifi- 

 cations, far more are above than below 17,000 feet, many are 

 18,000, and a few 19,000; besides which many extensive areas 

 m Guge, Nari, Nubra, Rupehu, and Zanskar, are continu- 

 ously above 15,000 feet for many miles in all directions. 



The climate of Western Tibet can only be approximately 

 ascertained, no continued records of temperature, humidity of 

 the air, or rain-fall, having ever been kept. Captain H. Stra- 

 chey has however reduced all the detached observations that 

 were procurable, and we are indebted to his valuable paper on 

 the Physical Geography of Western Tibet * for most of the 

 following data- 

 in the basin of the Indus at Le, elevated 11,800-12,000 

 feet, and 1300-1500 above the bed of the river, which is con- 

 siderably below the mean elevation of Western Tibet, and 

 in a sheltered locality, the mean temperature of the year is 

 assumed to be 35°: of January 10° (variation —5° to +25°), 

 and of July 60° (variation 50° to 70°) . Constant frost sets in 

 at that elevation early in November, and lasts till the end of 

 February ; but night-frosts continue till the middle of April, 



* Read before the Royal Geographical Society, November, 1853; 



