66 FROM CENTRAL TIBET TO LADAK.
which bears unmistakable evidences of carrying appreciable quantities of water after rain. On the strength of these orographical relations, and of the soundings which I made en route, certain general conclusions may be drawn with regard to the bottom relief of the western basin of the lake. The deeper channel which I have assumed to run quite close to the northern shore ought to be interrupted opposite to the end of the transverse glen by a belt of shallower water, not only because the temporary stream which courses down it ought to deposit the solid material it brings with it, but also because it has immediately south of it the large mud-delta, the flat, gently sloping »scree» of which possibly reaches as far as the northern shore of the lake. West of that shallow belt the deeper channel ought, on the other hand, to continue until it is succeeded by the shallow shore region in the extreme innermost bay on
the west.
This basin of the lake, which I have just cursorily described, narrows somewhat towards the north-east, and finally is bounded by a long promontory, little more than i m. broad, that juts out from the eastern shore, but slightly above the surface of the lake; it rises, however, a little towards its extremity, though not more than a couple of decimeters. It is built up of sand, and consequently is different from the three promontories that project from the southern shore of the island, for these are formed of mud, and point towards the east or south-east. Nor can this long sandy promontory be regarded as an immediate continuation of the nearest mountain-fork; everything is against that supposition — its consistency, its shape, and its position. If however the view which I have thrown out above is correct, that from the river-valley on the west there issued a glacier-arm, which, splitting against the mountainous upswelling of the island, continued as a double ice-stream, one branch proceeding north-east and the other south-east, it ought not to be considered too bold a supposition to look upon this circa too meter long pier-like projection as an old terminal moraine, which was formed at a time when the glacier in its westward retreat had reached the position that »the pier» now occupies. Its surface, like that of the »pier» at Camp LXXX, is very level, except for the slight elevation towards its extremity. It must be left to future investigators to solve this problem, and to determine how far my view is right or the reverse. Before continuing the further development of my view, I will finish my description of the »pier» itself.
The surface of this moraine ridge, unlike the surface of that at Camp LXXX, is barren, and it curves like a bow; in fact, it is shaped approximately like a scythe, with its concave side facing south-west, that is to say the mouth of the glen out of which the glacier formerly flowed. In the bay which is thus created on the south of the river-arm the lake-bottom lies, so to speak, flush with the water-level and is formed of soft ooze and decaying vegetable matter, clearly Alga and seaweed of the same description as those which we found in the cut-off deltaic arm ; it is carried thither by the movement of the current along the lake, but gets arrested on the way by the »pier», where it forms a mass of sludge. This promontory may be regarded as the boundary between two very unlike parts of the Naktsong-tso, being situated at the narrowest spot in that section of the lake, while east of it the lake spreads out into one of the largest continuous sheets of water that it possesses.
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