Thus in the short space of 4 years by far the greatest part of the volume had shifted over into the right deltaic arm. But the table appears to indicate that a return to the former condition of things has just begun. In i goo the proportion which the volume of the Tusun-tschapghan bore to the volume of the Kum-tschapghan was as 2.26 to I ; in 1901 as 1.65 to I . And while the former stream diminished by 3 cub.m., the latter increased by i cub.m. Just as the whole of the lower Tarim swings like a pendulum to and fro across the Desert of Lop, so too do these deltaic arms oscillate, although with a much shorter period. Plotted out on a map, the lowermost Tarim and its deltaic arms present the appearance of a tree, the main river being the stem, its arms the branches, and its lakes the crown of the tree. It is an »inland» delta, and in configuration is just as changeable and as capricious as a coastal delta. The measurements quoted above prove that the deltaic arms are travelling backwards up the river, whereas the lakes, as we shall see presently, are migrating towards the north.
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