6 EXPLORATIONS IN TURKKSTAN. 
Along the base of the southern mountains stretches a chain of narrow oases at 
the mouths of the mountain valleys ; there are other very narrow strips alonj^ the 
larger river courses, and more extensive areas inclosed between the projecting 
spurs of the eastern mountains ; all the rest of the basin has become the pre>- of 
the mo\ing sands, which are still ver\- slowly but surely invading the oases. The 
boundary is sharply defined ; within it is high cultivation ; beyond it is a sea of 
waves of sand. 
As they extend eastward the southern mountains increase in height, till both 
they and the great spurs of the Tian Shan, giant snow and ice co\-ered crests and 
peaks, dominate the oases which are the offspring of their waters. It is on these 
mountains of snow and ice that the life of the whole region is and has been from 
a remote period absolutely dependent. 
This life is also limited by another factor — itself a result of the desiccation — 
the moving sands. For, other things remaining equal, while the shrinkage of the 
water areas can continue only till equilibrium between supph' and evaporation is 
reached, and while there might be also cyclical periods of revivif\'ing afflux, these 
compensations are offset in the oa.ses by the slow but steadily overwhelming pro- 
gress of the sands. 
The progressive desiccation of Turkestan is shown by direct obser\-ations 
during the past centim-, by artificial landmarks, by historical statements, and by 
natural records. The Aibughir Gulf of the Aral was 133 kilometers long and 3,500 
square kilometers in area in 1842, and dr^' land in 1S72. 
The vohime of the Svr Darva has diminished greatly, as shown by the remains 
of old irrigating canals along its whole lower course, which are now too high to 
receive water. The statements of Arabian writers show that, within recent histor- 
ical times, there was a far more numerous population than the country could support 
now, when all available water is utilized. Old water-level lines occur at various 
heights up to 225 feet above the Aral. 
The progress is not uniform, but is broken by periods of temporarily increa.sed 
precipitation. Dorandt measured in 1874-75 a fall of 70 mm. in the year in the 
Aral Sea. Schultz, in comparing his surveys of 1880 with earlier maps, found a 
lowering of the level of 38 cm. in nine years. On the other hand. Berg, in 1901, 
comparing the gage established by Tillo, found the level 121 cm. higher than in 
1874. He calculates the total rise between 1882 and 1901 to be at least 3 meters, 
or 178 nun. yearly. 
Judging from our observations and from those of others, especially of the 
Arabian writers and of the later Russian explorers, it would seem that the country- 
has long been an interior region, dependent for its life mainly on the snows 
and glaciers of the mountains ; that there have been within the present geological 
period great fluctuations in the amount of water derived from the mountains, as 
recorded in high and low shorelines of the seas and in the strata containing living 
fonns left by difTerent expansions of the united waters of the Aral and Caspian, and 
that man already existed within the region during at least the last great maximum 
of moisture. 
