Pacific drainage area, which along the Huang-ho or Yellow river extends to the adjoining parts of the Kansu province and to the north-eastern uplands of Tibet. Favoured by the moisture which air currents from the Pacific Ocean carry up at different seasons of the year, abundant vegetation clothes the valleys from the westernmost limits of the drainage of the Su-chou river. To eyes accustomed to the barrenness of the K`un-lun it is an impressive experience to see the excellent summer grazing offered by the open valleys at the headwaters of the Su-chou and the Kan-chou rivers, notwithstanding the great elevation, in parts well over i r,000 feet. Still farther to the south-east increasing snow and rainfall permits of plentiful forest growth in the valleys drained by the Kan-chou river in the northernmost range of the Nan-shan (Fig. 4) .
We have now arrived close to the watershed of the region which the Huang-ho drains into the Pacific Ocean, and thus to the eastward border of that wide belt of innermost Asia with which we are dealing. This is strikingly brought home to us by the fact that from the edge of the Kan-chou oasis eastwards climatic conditions along the fertile foot of the Nan-shan permit of cultivation being carried on without irrigation and dependent on rain and snowfall only.
But none of this moisture reaches the ocean.
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From here we must turn back in order to complete our circuit of the mountains. Westwards of the Etsin-gol which carries the waters from the Nan-shan into a drainageless basin there extend the barren ranges and plateaux of the Pei-shan (the `Northern Mountains') . These merge into the equally arid hill chains known by the Turki name of Kuruk-tagh, the `Dry Mountains'. These again continue the
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