The bed of the Oxus in its lower reaches is muddy. Taking the course of the river as a whole, measurements which have been made at a series of points demonstrate that there are no less than 16,000,000 tons of sedimentary matter constantly passing down to form the vast delta that distinguishes its mouth, as well as to fertilise its banks or any areas which, from time to time, may be submerged. It is unnecessary to mention all the various channels through which, below the fortress of Nukus, the stream flows. The principal are the Ulkan Daria, the Taldik and the Yani Su. These present the usual features of a delta; but the triangular space contained within the Yani Su and the Taldik, its extreme eastern and western channels, is not a true delta, since it consists of an original formation through which the river has cut its way to the Aral sea, and upon which other matter has been deposited. Actual deltas, however, have been developed about the mouths of the Taldik and Yani Su, their existence constituting a bar to vessels drawing over 4 feet of water. [Illustration: VILLAGE ON THE LOWER OXUS] The tendency of the Oxus, like that of the great Siberian rivers, is to press continually on its right or east bank. The consequence of this deflection, which is due to the rotation of the earth round its axis from west to east, is that the stream has turned from the Kungrad channel eastwards to the Taldik channel and thence to the Yani Su which, at present, is receiving the main discharge. In former times a far greater deviation took place. No less than twice during its history has the Oxus oscillated between the Caspian and the Aral seas. In the time of Strabo it was a sort of eastern continuation of the Kura route from Georgia across the Caspian and the Kara Kum to Charjui. Its course across the desert is indicated by the Igdy and other wells dotted over the plains in a line with its former bed, which reached the Caspian in the depression between the Great and Little Balkan hills. Later on Edrisi found the Oxus flowing into the Aral. But in the fourteenth century it was flowing into the Caspian--this time along the Uzboi channel. The bed ran from near Nukus westwards to the Sara Kamish Steppe and thence southwards to the Igdy wells, along the original course between the Balkans to the Caspian, close to Mikhailovsk.