186C] Tableau of High Asia. 59 



the highest, remain open throughout the year. In some parts of 

 Tibet the winter is the only season, when atmospheric precipitation 

 at all takes place. 



In the Kunliln, even on its southern slopes, a greater amount of 

 snow is precipitated than on the northern side of the Karakorum, 

 whilst its Turkistani (northern) slopes differ still more from the 

 Karakorum in this respect, they being visited by very heavy rains and 

 great snow-falls. Even at Kashgar (about 3,500 ft ), in Turkistan, 

 there are said to be several snowy days every winter. 



The data, which I was able to collect on snow-fall in the Andes, are 

 so few and vague, that I could not draw any conclusion from them. 

 Also for the Alps, I could not bring forward any new facts with 

 reference to the snow-fall. 



2. Snow -line. 

 The snow-line, or the average height where snow remains perpetu- 

 ally throughout the year, lias offered unexpected difficulties in its de- 

 termination for the Himalaya. When Webb and Moorcroft first 

 pointed out the general heights reached by the snow-line, when they 

 first discovered the remarkable fact, that, in spite of the influence 

 arising from exposition, the snow-line of the Himalaya descends lower 

 on its southern (Indian) than on its northern (Tibetan) slopes, the 

 statements of these travellers, now proved to be correct in all material 

 points, were discredited by men of science both in Europe and in 

 India. Humboldt, however, was among the first who endeavoured 

 to remove the distrust with which these discoveries were received ; 

 he also gave an explanation* of the causes which were possibly suffi - 

 cient to originate so remarkable a phenomenon as this of the unlooked- 

 for differences existing between the snow-lines of the Tibetan and 

 Indian slopes. He considers it " the results conjointly of the radiation 

 of heat from the neighbouring elevated plains, the serenity of the sky, 

 and the infrequent formation of snow in very cold and dry air." Of 

 all these causes, however, the last is the most important. The direct 

 insolation, being less interrupted on the Tibetan side, has also its 

 share of influence ; but the effect is comparatively small. As the best 

 corroboration of the quantity of snow-fall being the principal cause of 

 the depression on the southern (Indian) slope of the Himalaya, may 

 * " Asie Centrale," pp. 284, 327 ; " Kosmos ; " Vol. I. p. 358. 



