bank of the stream that we touched every north-going winding at a tangent. Except at a couple of places only, the volume was always collected into a single channel, which retained its breadth almost unaltered. The banks are everywhere low, and the existing erosion terraces, which rise vertically or with a very steep slope from the water's edge, seldom reach more than one meter above it. The grazing improved, though it was confined to small patches and stretches along the banks. On the other hand, there runs on the left or northern bank of the river an old erosion terrace, which sometimes lies a score of meters or so distant from the existing bank and sometimes approaches so close to it, that there was only just room for the camels to march between the two. The terrace in question consists
of hard consolidated gravel, has a steep slope, and rises about 4 m. in height. It accompanied us all day, with but few interruptions. There exists a similar terrace on the opposite or right bank, and during the second half of the day's march this terrace was more developed than its vis-a-vis. These erosion terraces are memorials of a time when the Bogtsang-tsangpo exercised a far more energetic erosive activity than it does to-day; but the ascent of the latitudinal valley from the river's mouth in the Dagtse-tso is so exceedingly slight that at the present time one can scarcely speak with propriety of any actual erosion. If the lake possesses an absolute altitude of 4544 m., the rise up to Camp XCII (alt. 4623 m.), a distance of
IIIFカラー高解像度
