From the East Turkestan lowlands on the north the ascent is very steep, and the passes across both sets of ranges lie at great altitudes; for example, the pass of Sanju-davan in the lower range is 16,325 ft.
Above sea-level, and the Kyzyl-davan, farther east, is 16,900 ft., while the Sughetdavan in the higher range is 17,825 ft.
From the transverse breach of the Keriya-darya (about 811° E.) to that of the Kara-muren in the longitude of Cherchen (about 852° E.) the parallel border-ranges of the Tibetan plateau trend to the E.N.E., and here occur in the lower or outer range the passes of Dalai-kurghan-art (14,290 ft.), Choka-davan, i.e.
11,500 ft., while in the upper range are the At-to-davan (16,600 ft.), Yapkak-lik-davan (15,550 ft.), Sarshu-davan (15,680 ft.) and others not named at 16,590 and 17,300 ft.
(Tash-davan), though one pass beside the Charkhlik-su is only 9660 ft.
In the western part of this valley occurs the very important transverse water-divide of Gulcha-davan (14,150 ft.), which separates the basin of the Cherchen-darya that goes down into the Tarim basin from the area that drains down to the Ghaz-kol, which belongs to the Tsaidam depression.
In the Kalta-alaghan, which is the culminating range of this part of the Kuen-lun, and is overtopped by towering, snow-clad peaks, the passes climb to considerably higher altitudes, namely, 14,560, 1 4,47 0, 1 4,43 0 and 14,190 ft., while the pass of Avraz-davan ascends to 15,700 ft.
This range appears to be linked on to the Tokuz-davan by the Muzluk-tagh, in which there are passes at 16,870 and 15,450 ft.
Indeed Bogdanovich considers that the Tokuz-davan, the Muzluktagh, the Moscow Range and the Chimen-tagh form one single closely connected chain, in which he also places Przhevalsky's isolated peak of Mount Kreml (15,055 ft.).
After crossing the Kara muren davan in the Arka Tagh, they Dutreuil de entered the lake region of north Tibet and followed a Rhins and general southerly direction across low ranges of hills F., Grenard, 1893-1894.