CHAPTER XIV. 
GEOGRAPHICAL SUMMARY 
ARON VON RICHTHOFEN divides the whole 
I J of the Asiatic continent into three distinct regions 
of very unequal extent — the Central, in which the rivers 
drain into inland lakes ; the Peripheral or border lands, 
in which the streams make their way down to the seas 
which wash the coasts of the continent ; and the Transition 
or Intermediate tracts, which partake of the characteristics 
of the other two. The subdivision also holds good when 
applied to the Pamirs. Here too there are three similar 
geographical districts — a central district draining into lakes 
Kara-kul and Rang-kul, a peripheral draining to the Amu- 
daria (and so into Lake Aral) and to the Tarim (which 
empties into the lake Lop-nor). 
The most remarkable feature in the region of internal 
drainage is the process of levelling-up which goes on 
unceasingly. The detritus which results from the dis- 
integrating action of the weather, and the more or less 
mechanical agency of wind and water and gravity, is 
constantly being carried down from the mountains all round 
its borders towards the lower parts of its depressions, 
and being deposited there. In this way the natural in- 
equalities in the configuration of the ground are being 
gradually smoothed away. Although, broadly speaking, 
this process is going on in the tracts around Lake Kara- 
kul, it is also true that there are very great differences in 
the relative altitudes in that same quarter. For instance, 
the lake lies at an elevation of 13,000 feet above sea-level. 
It has been sounded to a depth of 756 feet, a remarkable 
depth considering that Kara-kul is a saline lake in the 
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