contained basin, Wellby's was fresh. Immediately east of the latter begins the Tschumar or Namchutu-ulan-muren. Wellby, after marching for some days beside this, turned away from it into eastern Tsajdam, Koko-nor, and Tenkar. In so doing he intersected the routes of Rockhill, Prschevalskij, and Krishna successively, and then gradually worked his way into regions that are relatively well known.
Wellby cannot however be considered to have solved in a satisfactory way the interesting hydrographical problem which here confronted him, namely the question as to where the sources of the Tschumar really are situated. For three days he marched along the northern shore of the freshwater lake, and then he says, under date 26th August, »A short distance from the lake we were lucky enough to strike another small stream, that took its rise from some of the neighbouring hills. This stream flowed away in an easterly direction, sometimes sluggish, at others fairly fast. The water was clear with a sandy bottom, a few yards across, and only about a foot deep. In some places we could see numbers of tiny fish, which always made off at our approach. The banks of this little stream were sandy and grassy. We decided, whatever happened, to follow it. By so doing we knew we must be descending the whole time, and what was more important still, we knew we should never suffer from scarcity of water.... We made a double and pleasant march along the stream, which all the time was increasing in volume.»
On the 29th August, thus barely three days after they left the lake, we are told that the river was so big that it would have been rash to attempt to ford it. Several days lower down Wellby fell in with a party of Tibetan traders, from the chief of whom he gleaned a good deal of information. »To our great astonishment and delight he informed us that the name of the river where we had first seen his camp was no other than the Chu Ma, the very one we had been in search of. Without being aware of it at the time, we had actually discovered the source of the Chu Ma just after leaving the beautiful freshwater lake. We had also followed its course for nearly twelve days, a distance of about 120 miles. This river is also known to the Tibetans as the Ma Chu, and to the Mongols as the Napchitai-ulen.»*
But though this brief description leaves us in uncertainty as to the exact situation of the source of the Tschumar, the map on the other hand makes the position quite plain. It is shown as starting a few miles east of the north-east corner of the lake; and that there may be no doubt about it, we read there the words, »Source of Chumar». Wellby is clearly of opinion, that the river has no sort of connection with the freshwater lake. Nevertheless everything seems to point to the river being an effluent from the lake, or more correctly speaking, the lake is merely a vast expansion of the river, and its true source must be looked for a long way farther west, in the vicinity of Wellby's camp of the 10th August. From that locality, which lies at an altitude of 5060 m., the river flows steadily east until it empties itself into the lake, the altitude of which is 4800 m. There are one or two little irregularities in the altitudes on the map which ought to have been eliminated, for between Camp 90 and Camp 91 the river is made to flow 5o m. uphill! Camp 97 lies at an altitude of
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