the gorge is joined by several similar ravines, all deeply cut and all without water. At length the gorge opened out again and we began to march along a level, slowly ascending swelling, that rises between two main watercourses, which unite to make the gorge I have just described. Here we found, though in insular patches, as in the main valley, fairly good grass, tall, but yellow and hard, such as it usually gets towards autumn. The valley was now inclosed between two small mountain-ranges, steeper and with sharply defined crests; in the southern one is the summit 02. The two main watercourses run each at the foot of one of these two ranges. The altitude of Camp XCI was 4637 ni. In its vicinity a hundred tame yaks were grazing; so that there were nomads in the neighbourhood. Our Tibetan attendants called this region Bigdo.
When we compare the three latitudinal valleys together, the following principal differences may be observed between them. The one farthest north is broad, open, and level, and possesses no distinct watercourse — according to Littledale. The middle one, which we were following, is considerably narrower, its floor very appreciably broken, and its watercourse energetically developed. The southern valley, along which the Bogtsang-tsangpo flows, is, according to the report of my Cossacks, in point of relief even more wild and inaccessible than the middle valley. These differences reflect on a small scale the peculiarities which on a large scale characterise the Tibetan highlands, that is to say in its central and more northerly parts predominantly plateau formations with open, flat, broad latitudinal valleys; but in the south a more accentuated relief, with narrow latitudinal valleys, more seldom plateau country. Nevertheless there do exist in Southern Tibet, at the northern foot of the Himalayas, plateau-like regions of the same kind as those which are so common at the southern foot of the Kwen-lun.
September 29th. We still continued up the latitudinal valley towards the west-south-west, at first ascending imperceptibly to a flat pass, only a couple of
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