1865.] Notes on Central Asia. 129 
range. Inthe same zone, parallel with the Celestial mountains the 
height of the snow-line is as follows : 
In the Pyrennees ; (between Lat. 422° and 43° North), ... 8,400 ft. 
On mounts Elburuz and Kazbek in the Caucasus (43° N, 
MAE NE eee Seatac iiss Lanse! URRY Ch spices dali sen ves 10,170 ft. 
Onmoncy Ararat) (uat. 39° North), oi. i0.c06. 00s... esecedenwe 13,300 ft. 
In the Rocky mountains of N. America (Lat. 43° N.)...... 11,700 ft. 
Humboldt, in his observations on my letter to Ritter, refers exclusively 
to the Pyrennees and to the Elburuz mountains. With regard to the 
first they cannot be taken at all into account in determining the height 
of the snow-line in the Celestial range, as they are situated in a moist 
sea atmosphere, where the snow-line must be considerably lower than 
in the continental climate of the interior of Asia. The Caucasus, 
however, supplies a better point of comparison, if treated with proper 
discrimination. The height of the snow-line of the Kazbek and 
Elburuz occurs at 10,170 feet, under a latitude of more than 1}° to 
the northward that that of the Tian-Shan, and with a climate consi- 
derably more humid. On mount Ararat, where the surrounding 
atmosphere is drier, and the latitude 24° more to the south, we find 
that the height of the snow-line is 13,300 feet above the level of the 
sea. Ifa range of mountains existed between the Elburuz and mount 
Ararat, under climatic conditions of an intermediate character as 
compared to those characterising mounts Ararat and Elburuz, and 
situated under the same parallel as the Celestial range, the height 
of the snow-line of these mountains would be determinable at 11,300 
feet. All these figures, computed theoretically by comparing the 
heights of the snow-line on different parallels of the same meridian with 
the Celestial mountains, and on different meridians of the same parallel, 
coincide very nearly with my determinations. The considerable 
elevation of the snow-line of the Celestial mountains is to be explained 
by the peculiarity of their geographical position, and the character 
of the surrounding atmosphere. It is generally admitted as a fact 
that a dry atmosphere has the effect of elevating the line of eternal 
snow very considerably. Thus for instance the snow-line on the 
southern slope of the Himalayas occurs at 12,180 feet, while on the 
northern side it rises to 15,600 feet. This anomaly is only to be 
accounted for by the southern side of the range being exposed to winds 
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