TO THE SATSCHU-TSANGPO: A PADDLE DOWN THE SAME. 19
must penetrate a little distance up most of them. It is owing to this that the layers of clay nearest to the river are more broken and crumbling, and consequently fall a readier prey to destruction.
After maintaining its constricted channel for no particularly great distance, the river widens out again, making room for long, narrow strips of alluvia. In some places the depth is so great, that the velocity is hardly perceptible. Here the river is joined from the right by a broad, dry watercourse, the bottom of which was overgrown with grass; while on the left there is a large gully, likewise dry, except for a pool in its throat. Some other similar watercourses come no doubt from the nearest hilly regions, though these are, it is true, a good way off. After a while the river describes a remarkably regular and wide-sweeping curve to the north-east. At the very apex of the loop it picks up a medium-sized tributary, which is unquestionably identical with an arm that branches off to the left just above Camp LXXIII.
After making a little bend to the south-south-west, the river turns due south — indeed it is amazingly straight for a river, and that in a place where one would expect an irregular delta with any number of arms, branching out all over the flat alluvial slope. The side-gullies now began to decrease in number; probably the systems of gullies that no doubt still exist on both sides make their way directly into the lake. On both banks of the river the scarped terraces are vertical and a couple of meters higher than before: at one place where we measured them they were 6.68 m. high. When they are not vertical, they are at all events so steep that it is almost everywhere impossible to climb up them. The river flowing between these escarpments still continues to bear a remarkable resemblance to an artificially dug canal, being amazingly straight and regular. The long narrow strips of sediment appeared above the water in only one or two places; but later in the year, in the autumn and winter, when the volume must be incomparably small, and the river frozen, these alluvial deposits will occupy a much more extensive area. The breadth was now increasing slowly, but constantly. At one point where the eroded banks reached an altitude of 8 meters, the breadth amounted to 400 m. ; while the depth almost everywhere was about a meter, and varied but slightly anywhere. After the point just indicated the breadth increased more rapidly, while at the same time the scarped banks decreased in height. At one spot, where the breadth amounted to at least 500 m., the bank was only 55 cm. high. A few hundred meters lower down it was 25 cm.; then, but for a very short distance, i m.; and after that it merged into the belt of flat alluvium that forms the lake-shore, though next the river there was still a distinctly visible edge barely i dm. high. During the last section of the river's course the banks are perfectly barren: not a single blade of grass was to be seen, the ground being a light yellow.
If ever the term »funnel-shaped» is correctly applied to the mouth of a river, then it certainly is here, where the Satschu-tsangpo enters the salt lake of Selling-tso. Straight as a die, almost as though its course had been drawn out with a ruler, flows the river towards the south, except that at its very end it makes a slight bend towards the south-south-west, while the breadth increases to r km., to i I/2 km., to 2 km., and the banks swing away to right and left and disappear as thin yellow lines,
IIIF Color HighRes
