THE LOP-NOR PROBLEM 877 
These measurements were made between April i8th and 
April 23rd. 
At Kum-chappgan the river splits up and becomes lost 
in a multitude of lakes and marshes, the largest of which, 
namely those in the middle, contain perfectly fresh water ; 
whilst in the lagoons all round the outsides the water is 
salt. The table above shows, that the breadth, the velocity 
of the current, and its volume all decrease as the river 
advances to the east ; whilst the depth increases. 
We have thus found that the quadruple Lop-nor of the 
Chinese has become refilled with water during the last nine 
years, whereas during the last twelve years the southern 
Lop-nor has dwindled to a series of shallow marshes. Is 
not the conclusion, therefore, not merely justified, but even 
forced upon us, that the two lake-systems are mutually 
related in an extraordinarily close and intimate way ; or in 
other words, as the northern Lop-nor increases, the southern 
Lop-nor decreases, and vice-versd. 
I cannot refrain from pointing to one or two other 
features which support the theory, that the lakes discovered 
by Przhevalsky are, geologically speaking, of quite recent 
origin. 
Each of the streams of East Turkestan which unite to 
form the Tarim is accompanied by belts of poplar forest 
along its banks. Even the Keriya-daria, which is now cut 
off from the Tarim system and becomes lost in the sand, is 
no exception to the rule. In places it possessed a poplar 
forest so thick as to be quite impenetrable. The forest 
generally begins at the point where the several rivers 
debouch upon the plains, and consequently on the border 
of the same climatic region. Now rivers count amongst 
the safest and most reliable means of transport in the 
geographical distribution of vegetable species. Hence it 
would be only reasonable to suppose, that in the district in 
which the tributaries of the Tarim converge, the poplar 
forest would be more abundant than anywhere else. Now, 
as a matter of fact, at the point of present convergence the 
forest suddenly ceases altogether. The last specimens of 
Popuhis diversifolia which I saw at Chegghelik-uy were 
