Prosperity of oases is wrought by two great factors, water-supply and geographical position. With the rivers of Central Asia, Murg-ab ranks fourth in volume and, unlike the Zerafshan, which feeds a myriad of oases along its course above ere nourishing the last, Murg-ab water flows to spread in full among the gardens of its delta. In it we find a river whose life-giving has been concentrated into one veined mass of gardens safely housed far out amid the dunes. The cities of Mery have thus long been favored with abundant water combined with sound protection by its wide surrounding desert. Alexander found it populous and full of wealth, and so did the Persians and afterwards the Arabs. And once
Fig. 488.—Map of the Murg-ab Delta. The Oasis of Merv.
the caravans had opened out their routes across the sand, Mery ranked as one of the world's great trade centers. Lying midway between the Caspian Sea and Roof of the World, it centers that whole region of ancient oases. By caravan from Meshed to Mery is less than 200 miles, from Khiva 300, from Paikent or Bokhara 19o, from Samarkand 300, and from Balkh 275, measured along the
route. .
In their peculiar state as oases of type I a, those of Mery must have been especially sensitive to climatic change. To begin with, we must believe that
IIIF Color HighRes
