280 CLIMATIC CONDITIONS OF THE GLACIAL EPOCH. 



once in large part occupied by water,* and of decidedly lower elevation 

 tlian the Khor Plateau. 



In all of the explored region of mountain chains forming the borders 

 of the Central Asiatic mass, the distribution of snow and ice is strictly 

 subordinated to those physical laws which have already been discussed 

 in this volume. The chain which is nearest the tropics, at whose south- 

 ern base no snow ever falls, but where during most of the year the heat 

 is intense, is the one where the glaciers are most extensively developed : 

 some occurring there are much larger than the grandest of the Alps them- 

 selves. As we penetrate farther in towards the centre of the elevated 

 region, we find ranges of immense elevation, regions of intense cold, and all 

 the requisites for extensive glaciation, except the most essential one of 

 all, abundant precipitation. Chains of mountains rising to more than 20,000 

 feet in height are only sparsely covered with snow at their very summits ; 

 large glacier systems are wanting altogether; and the snow line rises higher 

 and higher — not that we are approaching warmer regions, but because we 

 have come to parts of the country from which the precipitation has been 

 almost entirely cut off by the exterior ranges of mountains. Although we 

 seem to have in Central Asia all of those conditions which are considered by 

 most geologists as essential to the development of extensive glaciation, yet 

 the facts prove, beyond possibility of doubt, that this region of very low 

 mean temperature is by no means generally glaciated, but that, taken as 

 a whole, with the exception of the southern border — which is exceedingly 

 high and faces prevailing winds characterized by extreme moisture — the 

 occurrence of snow and glaciers is something very exceptional, and confined, 

 as a rule, to the higher portions of the highest ranges. A few facts may be 

 cited as illustrative of the truth of this statement, which might be supported 

 by a much longer array of them. 



In Leh, in Thibet, at an elevation of from 11,000 to 12,000 feet, so dry 

 is the climate that there are winters when no snow falls. At the same 

 place and in Lassa there are years when the entire amount of precipitation 

 does not exceed one inch.t 



Dr. Henderson remarks as follows in regard to the region traversed by 

 him after crossing the Himalaya, in going from Lahore to Yarkand : " The 

 line of perpetual snow in Ladak is probably not under 20,000 feet. On 



* See aiiti-., pp. 132, 133. 



t Hermann von Srli]aj;int\veit, in Reisen in Indien und Hocha.sien, Jena, 1872, Band III. p. 312. 



