Of the rivers traversing Bhutan, the most considerable is the Manas, flowing in its progress to the Brahmaputra under the walls of Tasgaon, below which it is unfordable.
The Lhobrak was finally identified with the Manas river, a geographical discovery of some importance.
Travelling by way of Khamba jong directly to Gyantse and Shigatse, he turned eastwards at the latter town, finished the survey of the Yamdok t'so, and crossed the Himalaya into the valley of the Lobratsangpo or Upper Manas river.
Along the south foot of the Tian-shan, and in the high valleys which intervene between the constituent ranges of that system, there exist numerous flourishing oases, such as Uch-turfan, Ak-su, Kucha, Korla, Kara-shahr, Hami, Barkul, Turfan, Urumchi, Manas and Kulja.
Glaciers occur also on Manas mount to the south of the town of Aulie-ata.