hypothesis, that the lake has a capacity of only 2,50o million cub.m., is at all events not too low; and that Kosloff's statements as to the enormous extension of the lake to the north-east may be entirely left out of account. On the basis that the length and breadth really are what I have assumed them to be, namely 1 oo and 25 km. respectively, and if the volume is 2,018 million cub.m., then the actual mean depth will be only o.si m., and this I regard as being very near the actual truth. If, again, the annual evaporation amounts to one meter or more, it follows as a direct consequence, that in the summer, when the evaporation is incomparably much more active than at other seasons of the year, exceptionally large areas of the lake must dry up completely, and water will remain only in the deepest basins, especially in that part of the lake which is traversed by the northern waterway, in which, as we have found, the mean depth was 2.7 m. At the present time this is the only part of the lake in which fishing is carried on, apart from the westernmost division of the southern waterway, where there is water all the year round. Hence it is easy to understand why the natives pay no heed to the desiccation of the other sections of the lake. The information I gleaned, already set forth above, agrees in every respect with the assumptions I have just made.
The great changes which are taking place in the country of Lop must be considered in common from several different points of view. For, if we merely take into account the hydrographical relations, and reflect that even Prschevalskij pronounced the Kara-koschun to be a dwindling lake, and remember that since his time it has gone on shrinking still further and to a very considerable degree, it does seem absurd, that now, when it is less than it ever has been before, it should overflow the bounds within which it has hitherto been confined. But if we take as the focus of the entire series of operations the solid material, which, transported by wind and water, has accumulated in its basin, then the overflow is no longer a matter for special remark, but is in the highest degree both natural and inevitable.
In Chapter XIX of vol. I I have made certain calculations with regard to the 35 marginal lakes on the right bank of the Tarim, and found that their area amounted to about 564 million square meters, or about one-quarter of the area of the Kara-koschun. Their combined capacity amounted to 2667 million cub.m., or rather more than that of the terminal lake, the reason being that their mean depth is as much as 4.73 m., or more than double the mean depth of the open parts of the Kara-koschun, and nearly six times as much as its assumed mean depth. These small marginal lakes have a very innocent appearance on the map, where their combined area is only equal to one-fourth the area of the terminal lake; but their volume is greater than that of the Kara-koschun, and that in the beginning of April, just after this basin has been filled by the high flood. The volume of these desert lakes does not however mean that that amount of water is abstracted annually from the Tarim, for several of them have their connection with the river severed for years together. The tribute they levy upon the Tarim, and hence the detriment they do to the Kara-koschun, is caused for the most part by their evaporation ; and that we have assumed to be equivalent to a layer of water one meter deep every year, or in other words a total amount of 564 cub.m. annually, or an average of 18 cub.m. in the second. The disappearance of these marginal lakes would mean an increase
Heflin, Journey in Central Asia. H. 27
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