m. In this case we may indeed speak legitimately of a transverse threshold across the great latitudinal valley; and on the east it descends by successive steps, though the height of each step is insignificant. Faunal life was represented by yaks, kulans, marmots, and ravens.
The river, beside which we were encamped, appeared to gather its waters from over a considerable area of the slopes of the Koko-schili. At the point where we forded it, it had the appearance of being the biggest stream that we had yet seen south of the Arka-tagh. Its breadth was 2 2 m., mean depth 0.6 m., mean velocity I m., and volume i 3 cub. m. in the second, and yet we crossed it at the period of the day when its flood is wont to be the smallest. Fresh marks on its eroded terraced banks showed plainly that quite recently it had indeed been twice as big. The river-valley is inclosed between two parallel ranges, which did not appear to have any direct connection with the main ranges; the one to the north was the larger. Hard rock cropped out pretty frequently; it consisted of schists, which split into slabs, and its dip was 74° towards the N. 20° E.
We travelled down beside this river; but leaving its delta at some distance to the east, and skirting the western end of the lake, we began to look for a pass across the Arka-tagh. It was high time we crossed it in search of the Mongols,
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