THE NAKTSONG-TSO, ITS SOUND, AND ITS WESTERN HALF. 63
sank into it a foot deep; but a little way from the water's edge it was dry and hard, and bore a sprinkling of thin grass. From the shape and consistency of this belt of sedimentary matter, it is hardly possible to err as to the manner of its origination. At the foot of each mountain-wall, both that on the north and that on the south, a long narrow bay runs towards the north-west; while between them comes a third, very much narrower. It was into this last that we drove our skiff. It soon ended at a point, and its upper part was excessively shallow. The bottom consisted entirely of mud and clay. However, it was easy to see that this formation was the deltaic arm of a river, which had laid down vast deposits of sediment, and these send out two long pier-like projections, flush with the surface of the water, and terminating in the south-east in a couple of points
that block the mouth of the river. I have already called attention to the extremely peculiar shape of the Naktsong-tso: it resembles a ring of water surrounding a large island placed excentrically in its south-western part. All the way from the moraine-ridge at Camp LXXX we have found the lake to consist of a narrow water-way, slightly increasing in breadth however towards the north-west. But here, in the western part of the lake, immediately north-west of basin No. I, the watery ring is interrupted by a river that enters it from the west and forms a delta reaching right across it. From the route I was following I was only able to observe this deltaic region from the distance, though, had time permitted, it would well have repaid a thorough examination.
My observations as to the distribution of the water and the characteristics of the river amount to this. The little branch of the stream that is inclosed between the mud piers», the one into which we drove our skiff, terminates, as I have said, in a point, and is thus cut off and dead, being in fact now nothing more than a bay of the lake, which has penetrated into an abandoned eroded bed. In the line of its continuation towards the N. 78° W. we perceived evidences of water. This showed, that this branch had been fed by a far bigger branch, and after a tramp of barely 400 m. across the deltaic mud we reached the right bank of the latter. It was however cut off and isolated from its fellow, although full of very muddy water, with a mean depth of I to 2 m. It formed a sharply defined channel, about I o to 15 m. broad, and was crowded with Algae and sea-weed. The water was however perfectly motionless: we were unable to detect even the slightest sign of a current. It was indeed at first surprising to find, that the water in a stationary, cutoff branch such as this was muddy; but the cause was I dare say the great number of wild-geese, wild-duck, and gulls that we observed swimming and diving on it, making no end of a quacking and screaming; it is no doubt they that stir up the mud at the bottom, as they hunt about amongst the Algae.
The mouth by which the river actually discharges at the present time lay some distance west of my route, and reaches the lake by two principal arms, and off them are a number of very low mud-islands and mud-banks. The amount of water in this river was at that time insignificant, only a couple of cubic meters at the most, so far at least as I was able to estimate it at a distance. Now it is perfectly self-evident, that the two detached branches farther east are either definitively cut off and abandoned, or are only used when the river rises exceptionally high.
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