and behind every terrace; at a few places it was even 1 m. deep. Between the furrows, there is no snow at all. Paths of wild animals are numerous. The antelopes are seen by the hundreds, and in larger flocks than ever. The kyangs come to this plain at another season, their dung was common but the animals were absent. Of nomads' visits, we only once saw the signs, viz. an old camping place. The mountains to the south are moderate; at two places they seemed to present an easy passage to the south. The hills to the north are somewhat higher, but not considerable. At noon a very strong wind began from W. S. W. Pan. 42 I A and B, Tab. 76, was drawn from this camp. It gives a representation of the contours of the low hills both south and north of the valley, the stretching of which, both westwards and eastwards, is readily visible.
On February 25th, we accomplished a section of the endless latitudinal valley in which we were at a loss to tell in what direction the ground was falling. Our course was a little north of due east and the distance, I o km.; Camp CCCXXXVIII we had found to be at 5,118 m., and Camp CCCXXXIX was at 5, I o8 m. The difference of 1 o m. would give a fall at a rate of I : I o00. During the march I was under the impression that the ground was rising eastwards, and only the next day, February 26//i, it became quite evident that we had passed, somewhere between the two last-mentioned camps, the transverse threshold of the latitudinal valley which, to the east, marks the boundary of the drainage area of Lemchung--tso. The principal erosion furrow of the latitudinal valley which we crossed between Camps CCCXXX VII and CCCXXX VIII, is obviously fed by small tributary beds from the southern and northern mountains. Then follows, east of Camp CCCXXXIII, the quite imperceptible threshold, east of which the small feeders from both sides join the principal bed flowing eastwards a short distance north of Camp CCCXXXIX.
The minimum temperature of the night, —20.2°, was somewhat higher than usual as it had snowed, and the night had been cloudy and windy. In the morning the whole ground was covered with a very thin sheet of snow and so were the hills to the north. The landscape had exactly the same morphological features as the days before. The ground no doubt was still rising a few kilometers before it reached the imperceptible water-parting. So much was perfectly clear already from the start, that this time we were not approaching a high pass, but only a transverse and very flat threshold of the same kind as in the autumn of 1906, in the latitudinal valley east of the Aksai-chin Lake. This is the great difference between high passes and flat thresholds in latitudinal valleys. Where such a valley is narrow, as between Camps CCCXXIX and CCCXXX, the transverse water-parting pass is very high; whilst when the valley is broad and open like a plain, the water-parting pass is extremely flat and low and, as a rule, difficult to determine; in the latter case the rise
of the floor of the valley is very gradual and slow, and may take several days. In fro
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