At Otrar, after receiving its last tributary, it is no more than 250 yards wide.

Below this point it continually dwindles, partly from evaporation, partly from the branch stream which it throws off right and left, of which the chief are the Cazala and the Kuvan Deria.

On its way through the desert it spreads but little fertility along its banks, which are in places high and arid, in others depressed and swampy.

The branch streams are of some service for irrigation; and it is possible that a scientific system might turn the water of the main channel to good account, and by its means redeem from the desert large tracts which have never yet been cultivated.

But no such system has hitherto been applied to the Sir, and it is doubtful whether success would attend it.