OASES. Su 
Prosperity of oases is wrought by two great factors, water-supply and geo- 
graphical 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 Merv 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 
4» Odontche Tepe: oe a5 
ae Siecieaely here oS. f 
Sultan Kala ;, ¢ one 
Qo Ghiaur Kala : 
° Bairaim-Ali 
Ne 
[3] Kurgan = P 
[Pees] High sandhills: 
| Low sand hills 
> 
Scale of miles 
10 20 

Fig. 488.—Map of the Murg-ab Delta. The Oasis of Merv. 
the caravans had opened out their routes across the sand, Merv 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 Merv is less than 200 miles, from Khiva 300, from Paikent or 
Bokhara 190, from Samarkand 300, and from Balkh 275, measured along the 
route. 
In their peculiar state as oases of type Ia, those of Merv must have been 
especially sensitive to climatic change. To begin with, we must believe that 
