and S. W., it again changes its direction and now runs W. N. W.— E. S. E. At 85° 2 5' East Long. I crossed it at Lamlung-la, 5 118 m. high, and a few kilometers further east in the deep transverse valley of Rong-chu, the upper Sa-chu. The group of Chomo-uchong belongs to it. Just east of the latter I crossed the range in Kule-la, 5088 m. high, obviously Ryder's Ku-la to which he gives 5091 m. Thence it continues nearly straight east, between the Raga-tsangpo and the Tsangpo-Brahmaputra where it has heen crossed by a Pundit in Cha-zang-la, and by Ryder's expedition in Gang-la. Still farther east the range is pierced by the great river at Ladse-dsong. East of Ladse-dsong the range runs on the southern side of the Tsangpo. Eastwards it probably continues much farther than 9 2 ° East Long., where it ends according to Burrard. This question has to be settled in the future. It would not be easy to say whether the section of the range which is situated to the east of Ladse-dsong and south of the Tsangpo belongs to Transhimalaya or Himalaya. I would say to both systems. For if we speak of the original tectonic structure it certainly is the prolongation of the Lunkar — Lunpo - gangri — Chomo - uchong fold and therefore belongs to the Transhimalayan system of earth-waves. But if we attach more importance to the orographical arrangement, it would perhaps be more correct to say that it is a part of the Himalayan system. In the latter case the Tsangpo should be regarded as the boundary between the two great mountain systems. In its eastern section the range may be said to be a bridge joining the Transhimalaya with the Himalaya, thus giving a new support to the name Transhimalaya.
We have now finished with the western region of Central Transhimalaya. The central part, as I have said before, is situated between the two meridional lines of rift-valleys between fractures and faults, and has been compressed and crumpled in a most violent way. Beginning in the south we find what I believe is the westernmost section of the Nien-chen-tang-la. It begins S. E. of Samye-la where it is pierced by the deep-cut valley of Rukyok. Some 20 km. farther east it is pierced by the upper Chaktak-tsangpo in a deep, wild gorge. Another 24 km. farther east I crossed it in Gyägong-la, 5490 m. high. W. N. W. of this pass it has some fairly high peaks which, like the great range farther north, were called Kanchung-gangri by the Tibetans. Some 78 km. farther east I crossed it in the pass Sao-lungring, 5387 m. high. Between the two last-mentioned passes at least a part of the range was called Lombo by my guides, a word that is certainly the same as Lunpo. Still, I have left it on the map as I heard it. The effluent from Amchok-tso, Dongmo-chu, pierces the range between rather high, partly snow-covered mountains.' Except the Rukyokand Chaktak-tsangpo, the Dongmo-chu seems to be the single river piercing the range in this region.
i In Vol. III, p. 295 it is said that the river leaves the lake from its N. E. corner, which of course is a misprint for S. E. corner.
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