Nain Singh explored the sources of the Indus and of the Upper Brahmaputra in the years 1865-1867; and in 1874-1875 he followed a line from the eastern frontiers of Kashmir to the Tengri Nor lake and thence to Lhasa, in which city he remained for some months.
The Alai range of the Pamir, continued by the Kokshaltau range and the Khan-tengri group of the Tian-shan, and the Sailughem range of the Altai, which is continued in the unnamed border-range of West Sayan (between the Bei-kem and the Us), belong to this category.
By the mountains Khan-tengri, Muz-art, Terskei, Eshik-bashi and Narat.
Of altitude in Khan-tengri, and are covered with snow and glaciers - the only pass through them being the Muzart.
The lake region is noted for a vast number of hot springs, which are widely distributed between the Himalayas and 34° N., but are most numerous to the west of Tengri Nor (north-west of Lhasa).
The southern portion, from Lake Pangong to Tengri Nor, is inhabited by pastoral tribes of Tibetans, and possesses a few hamlets, such as Ombo, Rudok and Senja jong.
The general structure of the trans-Himalayan chains appears to indicate that the main axis of upheaval of the whole vast mass of the Tibetan highlands is to be found on two approximately parallel lines, represented the one by the Kuen-lun and the other by a line which is more or less coincident with the watershed between India and the central lake region, extending from Lake Pangong to Tengri Nor, the plateau enclosed between the two being wrinkled by minor folds, of which the relative elevation is comparatively low, averaging from woo to 1500 ft.
For convenience of classification we may include in Khamdo a long strip of country extending along the northern border of the Lhasa territory of Lhorong jong and Larego as far as Tengri Nor, and bounded to the north by the Dang-la mountains, which is designated by Tibetans as Gyade or " the Chinese province."
The pastoral or Dokpa tribes, north and north-east of Tengri Nor, are also under its rule.
It continues through the central lake district to Tengri Nor and Lhasa.
On the second journey (1874) he started from Ladak, crossing the vast and elevated plateau by the Tengri Nor and other great lakes, and again reaching Lhasa on the 18th of November.
The travellers were able to push on as far as the north-eastern bank of the great Tengri Nor, which they reached on the 30th of November 1893.
Pursuing, amid great difficulties, his southerly course, he finally reached the western bank of Tengri Nor.
He confirmed the existence, long suspected, of a lofty mountain chain extending right across the country from the lake Tengri Nor (i.e.
Deposits of purer material (chic 'sale or water borax) occur at the lakes of Rudok, situated to the east of the Pugha district; also still farther to the east at the great lakes Tengri Nor, north of Lhasa, and several other places.
The former is worshipped by the Mongolians as Okkin Tengri, " the Virgin Goddess "; but in Tibet and China the role of the divine virgin is filled by Kwan Yin, a personification of Avalokitesvara as the heavenly word, who is often represented with a child in her arms. Srong Tsan Gampo has also become a saint, being looked upon as an incarnation of Avalokitesvara; and the description in the ecclesiastical historians of the measures he took for the welfare of his subjects do great credit to their ideal of the perfect Buddhist king.