From it the Oxus, or Amu, flows off to the west, and the Jaxartes, or Syr, to the north, through the Turki state of Khokand, while to the east the waters run down past Kashgar to the central desert of the Gobi, uniting with the streams from the northern slope of the Tibetan plateau that traverse the principalities of Yarkand and Khotan, which are also Turki.
It was perhaps this Philoponus who tried to save the Alexandrian library from the caliph Omar after Amu's victory in 639.
Two rivers only - the Syr and the Amu - succeed in getting across the desert and reaching the Sea of Aral.
The only tributaries which the Amu retains are those whose whole course is within the highlands.
One of the most striking instances of this is the very thick Cretaceous and Tertiary deposits which cover the bottom of the valley of the Vakhsh (right tributary of the Amu) and are continued for about 300 m.