appear in very rugged, rocky and irregular forms. The little limestone ridge continues eastwards until it is suddenly interrupted by a large meridional valley from the south, which opens up a distant view in this direction and shows, in the background, a dark range higher than the rest and of a rounded outline, indicating that it consists of another kind of rock. From this valley several gravelly beds come down, directed to the narrow gate to the north, from which the Bogtsang-tsangpo again comes out.
A little west of this valley, Pan. 98, Tab. 17, was taken. This sketch gives a much better idea of the general appearance of the country and its relief than any descriptions in words. To the N. 75° W. it shows Mount Lamar, and to the N. 53° W., Mount Karvung, and the southeastern ramifications and ridges of this group. To the N. i7° E. is the narrow transverse valley where the Bogtsang-tsanb f o pierces the mountains and again returns to the latitudinal valley we had followed hitherto. Just at the place where the river flows out of its rocky gate, Camp XCIII of 1 90 I was situated, about 3 km. N. W. of Camp LXXXV of 1906. The photos taken on the first occasion and published in Vol. IV of Scientific Results, should be corn-pared with this panorama. To the N. E. and E. N. E., we see the mountain ranges bounding the large valley of the river. The view to the north is brilliant. In the gate between the mountains, the river winds with its ribbon of blue ice and its yellow banks. In meanders, sometimes forming three quarters of a circle, the river seeks its way along the base of the northern mountains, proving that the ground of the latitudinal valley slowly falls to the north, as can also be seen on all the dry watercourses from the transverse valleys in the southern mountains. The northern mountains are wild and rugged with rocky shoulders and steep slopes; their screes and fans are steep and rounded and pierced by all the small tributary valleys and their erosion beds. The base of these screes and fans, is cut and eroded by the river. It seems curious that the stream, instead of sticking to the flat and open latitudinal valley where no obstacles rise in its course, accomplishes these extraordinary roundabout ways between the mountain groups north of this valley, sometimes piercing ranges of hard rock which ought to have been insurmountable obstacles in its way. This seemingly surprising arrangement can only be explained by a thorough geological survey of the whole region and a deep understanding of the history of the river. The river is old, it is almost dying. An insignificant secular upheaval of the ground in the midst of its course would cut it into two parts, the eastern of which would belong to the Dagtse-tso, the western forming a new self-contained basin. It is also surprising that the river has not had force enough to cut out a deep and well-defined bed, but is flowing in a very superficial way on the top of recent deposits in the valleys. Though it is diminishing by the general desiccation of the whole country, which also forces the lakes to dwindle, it is still
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