579 and to the Tsanyi-la, 5150 m., of BONVALOT, after which the range seems to follow the valley of Salwen to the east, S. E. and south.
In a smaller parallel range south of it, DE RHINS crossed Rejen - la, 5094 m. high. Parallel ridges, running east and west, are situated between Selling-tso and Addan-tso and were seen from the south by BOWER in 1891-92, and by me from
the north in 1901.
Along the southern shores of Addan-tso, Naktsang-tso or Tso-ngombo and Selling-tso, there is a range along the northern base of which BOWER travelled, and which farther east was crossed by LITTLEDALE in a nameless pass, 5004 m. high. It seems to come to an end at the western shore of Pam-tso.
The next range to the south runs along the northern shore of Mokieu - tso, Bul-tso, Ring-tso and Tengri-nor. It was crossed twice by BONVALOT, twice by DE RHINS, and twice by LITTLEDALE. BONVALOT's Kol-targa-la, 4700 m., belongs to it. It seems to come to an end north of Nakchu. Between these ranges are, as usual, several ridges and folds parallel with them.
The mountain system which borders the Selling-tso — Panggong-tso depression to the north, starts, as the preceding system which is situated south of the same depression, from the mountain knot north of Panggong-tso. Just north of Tso-nyak it can be clearly traced, but to the west of this point its orographical connection with other ranges in the neighbourhood cannot be settled with any degree of certainty. It cannot be told whether we have to deal with a bifurcation north of Tsonyak, or whether the systems north and south of the Selling-Panggong depression are originally parallel with one another, though deformed and unrecognizable by reason of denudation and erosion. Both systems belong to the same series of crustal folds as the Central Kara-korum. The northern one may well be the same as that crossed in Marsimik-la, 5593 m., and Demchur-la, 5580 m. N. E. of Tso-nyak it was traversed in Spanglung - la, 5180 m., by ZUGMAYER in 1906. Farther east it was crossed by DEASY in two nameless passes, 4770 and 5051 m. high. In this region it borders to the north the latitudinal valley of Tsanger-shar which I followed in I 90 I. Still farther E. S. E., south of Shemen - tso, DEASY crossed it at Chukyar, 5225 m. high. A short distance from there we come to the pass Chardo - mirdo, 5029 m. high, discovered by RAWLING in 1903. The Thachap-gangri group obviously is part of it. From here its stretching is uncertain, though it seems probable that I crossed it somewhere near Pankur, 4748 m., in 1908. Some 170 km. farther E. S. E. it may again be traced in the nameless pass of 5209 m. used by BOWER 1891-92. My pass Yumrang-lopchangs, 5032 m., 1906, and DE RHINS' Palou-la, 5134 m., belong to it. For a distance of 135 km. DE RHINS was able to trace it as he travelled along its southern base. Here follows BOwER's pass of 5 718 m., at Tagla-gapo. At a distance of another 120 km. east it has again been checked
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