130 Notes on Central Asia. [No. 3, 
charged with the humid vapours of the Indian Ocean, which settle on 
the cold mountain slopes in the form of snow, while the winds on the 
northern slopes of Thibet are completely free from moisture. The 
extraordinary dryness of the atmosphere of the Celestial mountains, 
compared to the Altai and Caucasus, is strikingly exemplified by the 
following instances. In the neighbourhood of Riddersk, in the Altai 
mountains, the dew falls so heavily that the horseman is completely 
drenched, when riding through the high grass, while in the sombre 
forests of the North-Western Altai, called locally Taigi, the atmos- 
phere is still more humid, and rain, during some summers, falls inces- 
santly. Now during the two years I spent in the Celestial mountains 
and Trans-Ili-Altai I positively saw no dew; notwithstanding that 
the summer of 1857 was remarkably wet, and the Altai was rendered 
impassable from this cause, the fall of rain was very small. In addi- 
tion, the very vegetation of the Tian-Shan bears evidence to the 
dryness of the surrounding air. 
While the slopes of the Caucasus are clothed with dark and impene- 
trable forests, which proved so troublesome in the military operations 
of the Russians, the wooded surfaces of the Tian-Shan are of limited 
extent, and rhododendrons, which are so widely spread in the moist 
climates of the southern slope of the Himalayas and of the Caucasus, 
do not grow at all in the Celestial range. 
If to this extraordinary dryness of the air inthe Celestial mountains, 
be added the intense heating of the broad plateau by the scorching 
rays of the sun, accompanied by cloudless skies and a rare atmosphere, 
a natural explanation will then be found for the height of the snow- 
line being at 11,000—11,500 feet. The few measurements of heights 
made by other travellers in Djungaria, and moreover by other methods, 
serve to confirm the accuracy of my figures. Fédorof determined 
trigonometrically, that is by the most accurate process, the altitude of 
the highest point in the Tarbagatai at about 9,900 feet. The Tarbagatai 
range extends under Lat. 47° N. and is consequently nearer by 1° of 
latitude to the Tigeretski Belki, than to the Celestial range. Com- 
puting the elevation of the snow-line of the Tarbagatai theoretically, 
by a comparison of the heights in the Altai and Tian-Shan, we should 
obtain a result of about 8,600 feet, while in reality the true elevation 
is considerably greater, as throughout the Tarbagatai range the existing 

